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1. Introduction: Our Journey Implementing a Micro Frontend

16 December 2021 at 17:08

Introduction: Our Journey Implementing a Micro Frontend

In the current world of frontend development, picking the right architecture and tech stack can be challenging. With all of the libraries, frameworks, and technologies available, it can seem (to say the least) overwhelming. Learning how other companies tackle a particular challenge is always beneficial to the community as a whole. Therefore, in this series, we hope to share the lessons we have learned in creating a successful micro-frontend architecture.

What This Series is About

While the term “micro-frontend” has been around for some time, the manner in which you build this type of architecture is ever evolving. New solutions and strategies are introduced all the time, and picking the one that is right for you can seem like an impossible task. This series focuses on creating a micro-frontend architecture by leveraging the NX framework and webpack’s module federation (released in webpack 5). We’ll detail each of our phases from start to finish, and document what we encountered along the way.

The series is broken up into the following articles:

  • Why We Implemented a Micro Frontend — Explains the discovery phase shown in the infographic above. It talks about where we started and, specifically, what our architecture used to look like and where the problems within that architecture existed. It then goes on to describe how we planned to solve our problems with a new architecture.
  • Introducing the Monorepo and NX — Documents the initial phase of updating our architecture, during which we created a monorepo built off the NX framework. This article focuses on how we leverage NX to identify which part of the repository changed, allowing us to only rebuild that portion.
  • Introducing Module Federation — Documents the next phase of updating our architecture, where we broke up our main application into a series of smaller applications using webpack’s module federation.
  • Module Federation — Managing Your Micro-Apps —Focuses on how we enhanced our initial approach to building and serving applications using module federation, namely by consolidating the related configurations and logic.
  • Module Federation — Sharing Vendor Code —Details the importance of sharing vendor library code between applications and some related best practices.
  • Module Federation — Sharing Library Code — Explains the importance of sharing custom library code between applications and some related best practices.
  • Building and Deploying — Documents the final phase of our new architecture where we built and deployed our application utilizing our new micro-frontend model.
  • Summary —Reviews everything we discussed and provides some key takeaways from this series.

Who is This For?

If you find yourself in any of the categories below, then this series is for you:

  • You’re an engineer just getting started, but you have a strong interest in architecture.
  • You’re a seasoned engineer managing an ever-growing codebase that keeps getting slower.
  • You’re a technical director and you’d like to see an alternative to how your teams work and ship their code.
  • You work with engineers on a daily basis, and you’d really like to understand what they mean when they say a micro-frontend.
  • You really just like to read!

In conclusion, read on if you want a better understanding of how you can successfully implement a micro-frontend architecture from start to finish.

How Articles are Structured

Each article in the series is split into two primary parts. The first half (overview, problem, and solution) gives you a high level understanding of the topic of discussion. If you just want to view the “cliff notes”, then these sections are for you.

The second half (diving deeper) is more technical in nature, and is geared towards those who wish to see how we actually implemented the solution. For most of the articles in this series, this section includes a corresponding demo repository that further demonstrates the concepts within the article.

Summary

So, let’s begin! Before we dive into how we updated our architecture, it’s important to discuss the issues we faced that led us to this decision. Check out the next article in the series to get started.


1. Introduction: Our Journey Implementing a Micro Frontend was originally published in Tenable TechBlog on Medium, where people are continuing the conversation by highlighting and responding to this story.

2. Why We Implemented A Micro Frontend

16 December 2021 at 17:11

Why We Implemented A Micro Frontend

This is post 2 of 9 in the series

  1. Introduction
  2. Why We Implemented a Micro Frontend
  3. Introducing the Monorepo & NX
  4. Introducing Module Federation
  5. Module Federation — Managing Your Micro-Apps
  6. Module Federation — Sharing Vendor Code
  7. Module Federation — Sharing Library Code
  8. Building & Deploying
  9. Summary

Overview

This article documents the discovery phase of our journey toward a new architecture. Like any engineering group, we didn’t simply wake up one day and decide it would be fun to rewrite our entire architecture. Rather, we found ourselves with an application that was growing exponentially in size and complexity, and discovered that our existing architecture didn’t support this type of growth for a variety of reasons. Before we dive into how we revamped our architecture to fix these issues, let’s set the stage by outlining what our architecture used to look like and where the problems existed.

Our Initial Architecture

When one of our core applications (Tenable.io) was first built, it consisted of two separate repositories:

  • Design System Repository — This contained all the global components that were used by Tenable.io. For each iteration of a given component, it was published to a Nexus repository (our private npm repository) leveraging Lerna. Package versions were incremented following semver (ex. 1.0.0). Additionally, it also housed a static design system site, which was responsible for documenting the components and how they were to be used.
  • Tenable.io Repository — This contained a single page application built using webpack. The application itself pulled down components from the Nexus repository according to the version defined in the package.json.

This was a fairly traditional architecture and served us well for some time. Below is a simplified diagram of what this architecture looked like:

The Problem

As our application continued to grow, we created more teams to manage individual parts of the application. While this was beneficial in the sense that we were able to work at a quicker pace, it also led to a variety of issues.

Component Isolation

Due to global components living in their own repository, we began encountering an issue where components did not always work appropriately when they were integrated into the actual application. While developing a component in isolation is nice from a developmental standpoint, the reality is that the needs of an application are diverse, and typically this means that a component must be flexible enough to account for these needs. As a result, it becomes extremely difficult to determine if a component is going to work appropriately until you actually try to leverage it in your application.

Solution #1 — Global components should live in close proximity to the code leveraging those components. This ensures they are flexible enough to satisfy the needs of the engineers using them.

Component Bugs & Breaking Changes

We also encountered a scenario where a bug was introduced in a given component but was not found or realized until a later date. Since component updates were made in isolation within another repository, engineers working on the Tenable.io application would only pull in updated components when necessary. When this did occur, they were typically jumping between multiple versions at once (ex. 1.0.0 to 1.4.5). When the team discovered a bug, it may have been from one of the versions in between (ex. 1.2.2). Trying to backtrack and identify which particular version introduced the bug was a time-consuming process.

Solution #2 — Updates to global components should be tested in real time against the code leveraging those components. This ensures the updates are backwards compatible and non-breaking in nature.

One Team Blocks All Others

One of the most significant issues we faced from an architectural perspective was the blocking nature of our deployments. Even though a large number of teams worked on different areas of the application that were relatively isolated, if just one team introduced a breaking change it blocked all the other teams.

Solution #3 — Feature teams should move at their own pace, and their impact on one another should be limited as much as possible.

Slow Development

As we added more teams and more features to Tenable.io, the size of our application continued to grow, as demonstrated below.

If you’ve ever been the one responsible for managing the webpack build of your application, you’ll know that the bigger your application gets, the slower your build becomes. This is simply a result of having more code that must be compiled/re-compiled as engineers develop features. This not only impacted local development, but our Jenkins build was also getting slower over time as things grew, because it had to lint, test, and build more and more over time. We employed a number of solutions in an attempt to speed up our build, including: The DLL Plugin, SplitChunksPlugin, Tweaking Our Minification Configuration, etc. However, we began realizing that at a certain point there wasn’t much more we could do and we needed a better way to build out the different parts of the application (note: something like parallel-webpack could have helped here if we had gone down a different path).

Solution #4 — Engineers should be capable of building the application quickly for development purposes regardless of the size of the application as it grows over time. In addition, Jenkins should be capable of testing, linting, and building the application in a performant manner as the system grows.

The Solution

At a certain point, we decided that our architecture was not satisfying our needs. As a result, we made the decision to update it. Specifically, we believed that moving towards a monorepo based on a micro-frontend architecture would help us address these needs by offering the following benefits:

  • Monorepo — While definitions vary, in our case a monorepo is a single repository that houses multiple applications. Moving to a monorepo would entail consolidating the Design System and the Tenable.io repositories into one. By combining them into one repository, we can ensure that updates made to components are tested in real time by the code consuming them and that the components themselves are truly satisfying the needs of our engineers.
  • Micro-Frontend — As defined here, a “Micro-frontend architecture is a design approach in which a front-end app is decomposed into individual, semi-independent ‘microapps’ working loosely together.” For us, this means splitting apart the Tenable.io application into multiple micro-applications (we’ll use this term moving forward). Doing this allows teams to move at their own pace and limit their impact on one another. It also speeds up the time to build the application locally by allowing engineers to choose which micro applications to build and run.

Summary

With these things in mind, we began to develop a series of architectural diagrams and roadmaps that would enable us to move from point A to point B. Keep in mind, though, at this point we were dealing with an enterprise application that was in active development and in use by customers. For anyone who has ever been through this process, trying to revamp your architecture at this stage is somewhat akin to changing a tyre while driving.

As a result, we had to ensure that as we moved towards this new architecture, our impact on the normal development and deployment of the application was minimal. While there were plenty of bumps and bruises along the way, which we will share as we go, we were able to accomplish this through a series of phases. In the following articles, we will walk through these phases. See the next article to learn how we moved to a monorepo leveraging the NX framework.


2. Why We Implemented A Micro Frontend was originally published in Tenable TechBlog on Medium, where people are continuing the conversation by highlighting and responding to this story.

3. Introducing The Monorepo & NX

16 December 2021 at 17:11

Introducing The Monorepo & NX

This is post 3 of 9 in the series

  1. Introduction
  2. Why We Implemented a Micro Frontend
  3. Introducing the Monorepo & NX
  4. Introducing Module Federation
  5. Module Federation — Managing Your Micro-Apps
  6. Module Federation — Sharing Vendor Code
  7. Module Federation — Sharing Library Code
  8. Building & Deploying
  9. Summary

Overview

In this next phase of our journey, we created a monorepo built off the NX framework. The focus of this article is on how we leverage NX to identify which part of the repository changed, allowing us to only rebuild that portion. As discussed in the previous article, our teams were plagued by a series of issues that we believed could be solved by moving towards a new architecture. Before we dive into the first phase of this new architecture, let’s recap one of the issues we were facing and how we solved it during this first phase.

The Problem

Our global components lived in an entirely different repository, where they had to be published and pulled down through a versioning system. To do this, we leveraged Lerna and Nexus, which is similar to how 3rd-party NPM packages are deployed and utilized. As a result of this model, we constantly dealt with issues pertaining to component isolation and breaking changes.

To address these issues, we wanted to consolidate the Design System and Tenable.io repositories into one. To ensure our monorepo would be fast and efficient, we also introduced the NX framework to only rebuild parts of the system that were impacted by a change.

The Solution

The Monorepo Is Born

The first step in updating our architecture was to bring the Design System into the Tenable.io repository. This involved the following:

  • Design System components — The components themselves were broken apart into a series of subdirectories that all lived under libs/design-system. In this way, they could live alongside our other Tenable.io specific libraries.
  • Design System website — The website (responsible for documenting the components) was moved to live alongside the Tenable.io application in a directory called apps/design-system.

The following diagram shows how we created the new monorepo based on these changes.

It’s important to note that at this point, we made a clear distinction between applications and libraries. This distinction is important because we wanted to ensure a clear import order: that is, we wanted applications to be able to consume libraries but never the other way around.

Leveraging NX

In addition to moving the design system, we also wanted the ability to only rebuild applications and libraries based on what was changed. In a monorepo where you may end up having a large number of applications and libraries, this type of functionality is critical to ensure your system doesn’t grow slower over time.

Let’s use an example to demonstrate the intended functionality: In our example, we have a component that is initially only imported by the Design System site. If an engineer changes that component, then we only want to rebuild the Design System because that’s the only place that was impacted by the change. However, if Tenable.io was leveraging that component as well, then both applications would need to be rebuilt. To manage this complexity, we rebuilt the repository using NX.

So what is NX? NX is a set of tools that enables you to separate your libraries and applications into what NX calls “workspaces”. Think of a workspace as an area in your repository (i.e. a directory) that houses shared code (an application, a utility library, a component library, etc.). Each workspace has a series of commands that can be run against it (build, serve, lint, test, etc.). This way when a workspace is changed, the nx affected command can be run to identify any other workspace that is impacted by the update. As demonstrated here, when we change Component A (living in the design-system/components workspace) and run the affected command, NX indicates that the following three workspaces are impacted by that change: design-system/components, Tenable.io, and Design System. This means that both the Tenable.io and Design System applications are importing that component.

This type of functionality is critical for a monorepo to work as it scales in size. Without this your automation server (Jenkins in our case) would grow slower over time because it would have to rebuild, re-lint, and re-test everything whenever a change was made. If you want to learn more about how NX works, please take a look at this write up that explains some of the above concepts in more detail.

Diving Deeper

Before You Proceed: The remainder of this article is very technical in nature and is geared towards engineers who wish to learn more about how NX works and the way in which things can be set up. If you wish to see the code associated with the following section, you can check it out in this branch.

At this point, our repository looks something like the structure of defined workspaces below:

Apps

  • design-system — The static site (built off of Gatsby) that documents our global components.
  • tenable-io — Our core application that was already in the repository.

Libs

  • design-system/components — A library that houses our global components.
  • design-system/styles — A library that is responsible for setting up our global theme provider.
  • tenable-io/common — The pre-existing shared code that the Tenable.io application was leveraging and sharing throughout the application.

To reiterate, a workspace is simply a directory in your repository that houses shared code that you want to treat as either an application or a library. The difference here is that an application is standalone in nature and shows what your consumers see, whereas a library is something that is leveraged by n+ applications (your shared code). As shown below, each workspace can be configured with a series of targets (build, serve, lint, test) that can be run against it. This way if a change has been made that impacts the workspace and we want to build all of them, we can tell NX to run the build target (line 6) for all affected workspaces.

At this point, our two demo applications resemble the screenshots below. As you can see, there are three library components in use. These are the black, gray, and blue colored blocks on the page. Two of these come from the design-system/components workspace (Test Component 1 & 2), and the other comes from tenable-io/common (Tenable.io Component). These components will be used to demonstrate how applications and libraries are leveraged and relate to one another in the NX framework.

The Power Of NX

Now that you know what our demo application looks like, it’s time to demonstrate the importance of NX. Before we make any updates, we want to showcase the dependency graph that NX uses when analyzing our repository. By running the command nx dep-graph, the following diagram appears and indicates how our various workspaces are related. A relationship is established when one app/lib imports from another.

We now want to demonstrate the true power and purpose of NX. We start by running the nx affected:apps and nx affected:libs command with no active changes in our repository. Shown below, no apps or libs are returned by either of these commands. This indicates that there are no changes currently in our repository, and, as a result, nothing has been affected.

Now we will make a slight update to our test-component-1.tsx file (line 19):

If we re-run the affected commands above we see that the following apps/lib are impacted: design-system, tenable-io, and design-system/components:

Additionally, if we run nx affected:dep-graph we see the following diagram. NX is showing us the above command in visual form, which can be helpful in understanding why the change you made impacted a given application or library.

With all of this in place, we can now accomplish a great deal. For instance, a common scenario (and one our initial goals from the previous article) is to run tests for just the workspaces actually impacted by a code change. If we change a global component, we want to run all the unit tests that may have been impacted by that change. This way, we can ensure that our update is truly backwards compatible (which gets harder and harder as a component is used in more locations). We can accomplish this by running the test target on the affected workspaces:

Summary

Now you are familiar with how we set up our monorepo and incorporated the NX framework. By doing this, we were able to accomplish two of the goals we started with:

  1. Global components should live in close proximity to the code leveraging those components. This ensures they are flexible enough to satisfy the needs of the engineers using them.
  2. Updates to global components should be tested in real time against the code leveraging those components. This ensures the updates are backwards compatible and non-breaking in nature.

Once we successfully set up our monorepo and incorporated the NX framework, our next step was to break apart the Tenable.io application into a series of micro applications that could be built and deployed independently. See the next article in the series to learn how we did this and the lessons we learned along the way.


3. Introducing The Monorepo & NX was originally published in Tenable TechBlog on Medium, where people are continuing the conversation by highlighting and responding to this story.

4. Introducing Module Federation

16 December 2021 at 17:13

Introducing Module Federation

This is post 4 of 9 in the series

  1. Introduction
  2. Why We Implemented a Micro Frontend
  3. Introducing the Monorepo & NX
  4. Introducing Module Federation
  5. Module Federation — Managing Your Micro-Apps
  6. Module Federation — Sharing Vendor Code
  7. Module Federation — Sharing Library Code
  8. Building & Deploying
  9. Summary

Overview

As discussed in the previous article, the first step in updating our architecture involved the consolidation of our two repositories into one and the introduction of the NX framework. Once this phase was complete, we were ready to move to the next phase: the introduction of module federation for the purposes of breaking our Tenable.io application into a series of micro-apps.

The Problem

Before we dive into what module federation is and why we used it, it’s important to first understand the problem we wanted to solve. As demonstrated in the following diagram, multiple teams were responsible for individual parts of the Tenable.io application. However, regardless of the update, everything went through the same build and deployment pipeline once the code was merged to master. This created a natural bottleneck where each team was reliant on any change made previously by another team.

This was problematic for a number of reasons:

  • Bugs — Imagine your team needs to deploy an update to customers for your particular application as quickly as possible. However, another team introduced a relatively significant bug that should not be deployed to production. In this scenario, you either have to wait for the other team to fix the bug or release the code to production while knowingly introducing the bug. Neither of these are good options.
  • Slow to lint, test and build — As discussed previously, as an application grows in size, things such as linting, testing, and building inevitably get slower as there is simply more code to deal with. This has a direct impact on your automation server/delivery pipeline (in our case Jenkins) because the pipeline will most likely get slower as your codebase grows.
  • E2E Testing Bottleneck — End-to-end tests are an important part of an enterprise application to ensure bugs are caught before they make their way to production. However, running E2E tests for your entire application can cause a massive bottleneck in your pipeline as each build must wait on the previous build to finish before proceeding. Additionally, if one team’s E2E tests fail, it blocks the other team’s changes from making it to production. This was a significant bottleneck for us.

The Solution

Let’s discuss why module federation was the solution for us. First, what exactly is module federation? In a nutshell, it is webpack’s way of implementing a micro-frontend (though it’s not limited to only implementing frontend systems). More specifically, it enables us to break apart our application into a series of smaller applications that can be developed and deployed individually, and then put back together into a single application. Let’s analyze how our deployment model above changes with this new approach.

As shown below, multiple teams were still responsible for individual parts of the Tenable.io application. However, you can see that each individual application within Tenable.io (the micro-apps) has its own Jenkins pipeline where it can lint, test, and build the code related to that individual application. But how do we know which micro-app was impacted by a given change? We rely on the NX framework discussed in the previous article. As a result of this new model, the bottleneck shown above is no longer an issue.

Diving Deeper

Before You Proceed: The remainder of this article is very technical in nature and is geared towards engineers who wish to learn more about how module federation works and the way in which things can be set up. If you wish to see the code associated with the following section, you can check it out in this branch.

Diagrams are great, but what does a system like this actually look like from a code perspective? We will build off the demo from the previous article to introduce module federation for the Tenable.io application.

Workspaces

One of the very first changes we made was to our NX workspaces. New workspaces are created via the npx create-nx-workspace command. For our purposes, the intent was to split up the Tenable.io application (previously its own workspace) into three individual micro-apps:

  • Host — Think of this as the wrapper for the other micro-apps. Its primary purpose is to load in the micro-apps.
  • Application 1 — Previously, this was apps/tenable-io/src/app/app-1.tsx. We are now going to transform this into its own individual micro-app.
  • Application 2 — Previously, this was apps/tenable-io/src/app/app-2.tsx. We are now going to transform this into its own individual micro-app.

This simple diagram illustrates the relationship between the Host and micro-apps:

Let’s analyze a before and after of our workspace.json file that shows how the tenable-io workspace (line 5) was split into three (lines 4–6).

Before (line 5)

After (lines 4–6)

Note: When leveraging module federation, there are a number of different architectures you can leverage. In our case, a host application that loaded in the other micro-apps made the most sense for us. However, you should evaluate your needs and choose the one that’s best for you. This article does a good job in breaking these options down.

Workspace Commands

Now that we have these three new workspaces, how exactly do we run them locally? If you look at the previous demo, you’ll see our serve command for the Tenable.io application leveraged the @nrwl/web:dev-server executor. Since we’re going to be creating a series of highly customized webpack configurations, we instead opted to leverage the @nrwl/workspace:run-commands executor. This allowed us to simply pass a series of terminal commands that get run. For this initial setup, we’re going to leverage a very simple approach to building and serving the three applications. As shown in the commands below, we simply change directories into each of these applications (via cd apps/…), and run the npm run dev command that is defined in each of the micro-app’s package.json file. This command starts the webpack dev server for each application.

The serve target for host — Kicks off the dev servers for all 3 apps
Dev command for host — Applications 1 & 2 are identical

At this point, if we run nx serve host (serve being one of the targets defined for the host workspace) it will kick off the three commands shown on lines 10–12. Later in the article, we will show a better way of managing multiple webpack configurations across your repository.

Webpack Configuration — Host

The following configuration shows a pretty bare bones implementation for our Host application. We have explained the various areas of the configuration and their purpose. If you are new to webpack, we recommend you read through their getting started documentation to better understand how webpack works.

Some items of note include:

  • ModuleFederationPlugin — This is what enables module federation. We’ll discuss some of the sub properties below.
  • remotes — This is the primary difference between the host application and the applications it loads in (application 1 and 2). We define application1 and application2 here. This tells our host application that there are two remotes that exist and that can be loaded in.
  • shared — One of the concepts you’ll need to get used to in module federation is the concept of sharing resources. Without this configuration, webpack will not share any code between the various micro-applications. This means that if application1 and application2 both import react, they each will use their own versions. Certain libraries (like the ones defined here) only allow you to load one version of the library for your application. This can cause your application to break if the library gets loaded in more than once. Therefore, we ensure these libraries are shared and only one version gets loaded in.
  • devServer — Each of our applications has this configured, and it serves each of them on their own unique port. Note the addition of the Access-Control-Allow-Origin header: this is critical for dev mode to ensure the host application can access other ports that are running our micro-applications.

Webpack Configuration — Application

The configurations for application1 and application2 are nearly identical to the one above, with the exception of the ModuleFederationPlugin. Our applications are responsible for determining what they want to expose to the outside world. In our case, the exposes property of the ModuleFederationPlugin defines what is exposed to the Host application when it goes to import from either of these. This is the exposes property’s purpose: it defines a public API that determines which files are consumable. So in our case, we will only expose the index file (‘.’) in the src directory. You’ll see we’re not defining any remotes, and this is intentional. In our setup, we want to prevent micro-applications from importing resources from each other; if they need to share code, it should come from the libs directory.

In this demo, we’re keeping things as simple as possible. However, you can expose as much or as little as you want based on your needs. So if, for example, we wanted to expose an individual component, we could do that using the following syntax:

Initial Load

When we run nx serve host, what happens? The entry point for our host application is the index.js file shown below. This file imports another file called boostrap.js. This approach avoids the error “Shared module is not available for eager consumption,” which you can read more about here.

The bootstrap.js file is the real entry point for our Host application. We are able to import Application1 and Application2 and load them in like a normal component (lines 15–16):

Note: Had we exposed more specific files as discussed above, our import would be more granular in nature:

At this point, you might think we’re done. However, if you ran the application you would get the following error message, which tells us that the import on line 15 above isn’t working:

Loading The Remotes

To understand why this is, let’s take a look at what happens when we build application1 via the webpack-dev-server command. When this command runs, it actually serves this particular application on port 3001, and the entry point of the application is a file called remoteEntry.js. If we actually go to that port/file, we’ll see something that looks like this:

In the module federation world, application 1 & 2 are called remotes. According to their documentation, “Remote modules are modules that are not part of the current build and loaded from a so-called container at the runtime”. This is how module federation works under the hood, and is the means by which the Host can load in and interact with the micro-apps. Think of the remote entry file shown above as the public interface for Application1, and when another application loads in the remoteEntry file (in our case Host), it can now interact with Application1.

We know application 1 and 2 are getting built, and they’re being served up at ports 3001 and 3002. So why can’t the Host find them? The issue is because we haven’t actually done anything to load in those remote entry files. To make that happen, we have to open up the public/index.html file and add those remote entry files in:

Our host specifies the index.html file
The index.html file is responsible for loading in the remote entries

Now if we run the host application and investigate the network traffic, we’ll see the remoteEntry.js file for both application 1 and 2 get loaded in via ports 3001 and 3002:

Summary

At this point, we have covered a basic module federation setup. In the demo above, we have a Host application that is the main entry point for our application. It is responsible for loading in the other micro-apps (application 1 and 2). As we implemented this solution for our own application we learned a number of things along the way that would have been helpful to know from the beginning. See the following articles to learn more about the intricacies of using module federation:


4. Introducing Module Federation was originally published in Tenable TechBlog on Medium, where people are continuing the conversation by highlighting and responding to this story.

5. Module Federation — Managing Your Micro-Apps

16 December 2021 at 17:15

Module Federation — Managing Your Micro-Apps

This is post 5 of 9 in the series

  1. Introduction
  2. Why We Implemented a Micro Frontend
  3. Introducing the Monorepo & NX
  4. Introducing Module Federation
  5. Module Federation — Managing Your Micro-Apps
  6. Module Federation — Sharing Vendor Code
  7. Module Federation — Sharing Library Code
  8. Building & Deploying
  9. Summary

Overview

The Problem

When you first start using module federation and only have one or two micro-apps, managing the configurations for each app and the various ports they run on is simple.

As you progress and continue to add more micro-apps, you may start running into issues with managing all of these micro-apps. You will find yourself repeating the same configuration over and over again. You’ll also find that the Host application needs to know which micro-app is running on which port, and you’ll need to avoid serving a micro-app on a port already in use.

The Solution

To reduce the complexity of managing these various micro-apps, we consolidated our configurations and the serve command (to spin up the micro-apps) into a central location within a newly created tools directory:

Diving Deeper

Before You Proceed: The remainder of this article is very technical in nature and is geared towards engineers who wish to learn more about how we dealt with managing an ever growing number of micro-apps. If you wish to see the code associated with the following section, you can check it out in this branch.

The Serve Command

One of the most important things we did here was create a serve.js file that allowed us to build/serve only those micro-apps an engineer needed to work on. This increased the speed at which our engineers got the application running, while also consuming as little local memory as possible. Below is a general breakdown of what that file does:

You can see in our webpack configuration below where we send the ready message (line 193). The serve command above listens for that message (line 26 above) and uses it to keep track of when a particular micro-app is done compiling.

Remote Utilities

Additionally, we created some remote utilities that allowed us to consistently manage our remotes. Specifically, it would return the name of the remotes along with the port they should run on. As you can see below, this logic is based on the workspace.json file. This was done so that if a new micro-app was added it would be automatically picked up without any additional configuration by the engineer.

Putting It All Together

Why was all this necessary? One of the powerful features of module federation is that all micro-apps are capable of being built independently. This was the purpose of the serve script shown above, i.e. it enabled us to spin up a series of micro-apps based on our needs. For example, with this logic in place, we could accommodate a host of various engineering needs:

  • Host only — If we wanted to spin up the Host application we could run npm run serve (the command defaults to spinning up Host).
  • Host & Application1 — If we wanted to spin up both Host and Application1, we could run npm run serve --apps=application-1.
  • Application2 Only — If we already had the Host and Application1 running, and we now wanted to spin up Application2 without having to rebuild things, we could run npm run serve --apps=application-2 --appOnly.
  • All — If we wanted to spin up everything, we could run npm run serve --all.

You can easily imagine that as your application grows and your codebase gets larger and larger, this type of functionality can be extremely powerful since you only have to build the parts of the application related to what you’re working on. This allowed us to speed up our boot time by 2x and our rebuild time by 7x, which was a significant improvement.

Note: If you use Visual Studio, you can accomplish some of this same functionality through the NX Console extension.

Loading Your Micro-Apps — The Static Approach

In the previous article, when it came to importing and using Application 1 and 2, we simply imported the micro-apps at the top of the bootstrap file and hard coded the remote entries in the index.html file:

Application 1 & 2 are imported at the top of the file, which means they have to be loaded right away
The moment our app loads, it has to load in the remote entry files for each micro-app

However in the real world, this is not the best approach. By taking this approach, the moment your application runs, it is forced to load in the remote entry files for every single micro-app. For a real world application that has many micro-apps, this means the performance of your initial load will most likely be impacted. Additionally, loading in all the micro-apps as we’re doing in the index.html file above is not very flexible. Imagine some of your micro-apps are behind feature flags that only certain customers can access. In this case, it would be much better if the micro-apps could be loaded in dynamically only when a particular route is hit.

In our initial approach with this new architecture, we made this mistake and paid for it from a performance perspective. We noticed that as we added more micro-apps, our initial load was getting slower. We finally discovered the issue was related to the fact that we were loading in our remotes using this static approach.

Loading Your Micro-Apps — The Dynamic Approach

Leveraging the remote utilities we discussed above, you can see how we pass the remotes and their associated ports in the webpack build via the REMOTE_INFO property. This global property will be accessed later on in our code when it’s time to load the micro-apps dynamically.

Once we had the necessary information we needed for the remotes (via the REMOTE_INFO variable), we then updated our bootstrap.jsx file to leverage a new component we discuss below called <MicroApp />. The purpose of this component was to dynamically attach the remote entry to the page and then initialize the micro-app lazily so it could be leveraged by Host. You can see the actual component never gets loaded until we hit a path where it is needed. This ensures that a given micro-app is never loaded in until it’s actually needed, leading to a huge boost in performance.

The actual logic of the <MicroApp /> component is highlighted below. This approach is a variation of the example shown here. In a nutshell, this logic dynamically injects the <script src=”…remoteEntry.js”></script> tag into the index.html file when needed, and initializes the remote. Once initialized, the remote and any exposed component can be imported by the Host application like any other import.

Summary

By making the changes above, we were able to significantly improve our overall performance. We did this by only loading in the code we needed for a given micro-app at the time it was needed (versus everything at once). Additionally, when our team added a new micro-app, our script was capable of handling it automatically. This approach allowed our teams to work more efficiently, and allowed us to significantly reduce the initial load time of our application. See the next article to learn about how we dealt with our vendor libraries.


5. Module Federation — Managing Your Micro-Apps was originally published in Tenable TechBlog on Medium, where people are continuing the conversation by highlighting and responding to this story.

6. Module Federation — Sharing Vendor Code

16 December 2021 at 17:16

Module Federation — Sharing Vendor Code

This is post 6 of 9 in the series

  1. Introduction
  2. Why We Implemented a Micro Frontend
  3. Introducing the Monorepo & NX
  4. Introducing Module Federation
  5. Module Federation — Managing Your Micro-Apps
  6. Module Federation — Sharing Vendor Code
  7. Module Federation — Sharing Library Code
  8. Building & Deploying
  9. Summary

Overview

This article focuses on the importance of sharing vendor library code between applications and some related best practices.

The Problem

One of the most important aspects of using module federation is sharing code. When a micro-app gets built, it contains all the files it needs to run. As stated by webpack, “These separate builds should not have dependencies between each other, so they can be developed and deployed individually”. In reality, this means if you build a micro-app and investigate the files, you will see that it has all the code it needs to run independently. In this article, we’re going to focus on vendor code (the code coming from your node_modules directory). However, as you’ll see in the next article of the series, this also applies to your custom libraries (the code living in libs). As illustrated below, App A and B both use vendor lib 6, and when these micro-apps are built they each contain a version of that library within their build artifact.

Why is this important? We’ll use the diagram below to demonstrate. Without sharing code between the micro-apps, when we load in App A, it loads in all the vendor libraries it needs. Then, when we navigate to App B, it also loads in all the libraries it needs. The issue is that we’ve already loaded in a number of libraries when we first loaded App A that could have been leveraged by App B (ex. Vendor Lib 1). From a customer perspective, this means they’re now pulling down a lot more Javascript than they should be.

The Solution

This is where module federation shines. By telling module federation what should be shared, the micro-apps can now share code between themselves when appropriate. Now, when we load App B, it’s first going to check and see what App A already loaded in and leverage any libraries it can. If it needs a library that hasn’t been loaded in yet (or the version it needs isn’t compatible with the version App A loaded in), then it proceeds to load its own. For example, App A needs Vendor lib 5, but since no other application is using that library, there’s no need to share it.

Sharing code between the micro-apps is critical for performance and ensures that customers are only pulling down the code they truly need to run a given application.

Diving Deeper

Before You Proceed: The remainder of this article is very technical in nature and is geared towards engineers who wish to learn more about sharing vendor code between your micro-apps. If you wish to see the code associated with the following section, you can check it out in this branch.

Now that we understand how libraries are built for each micro-app and why we should share them, let’s see how this actually works. The shared property of the ModuleFederationPlugin is where you define the libraries that should be shared between the micro-apps. Below, we are passing a variable called npmSharedLibs to this property:

If we print out the value of that variable, we’ll see the following:

This tells module federation that the three libraries should be shared, and more specifically that they are singletons. This means it could actually break our application if a micro-app attempted to load its own version. Setting singleton to true ensures that only one version of the library is loaded (note: this property will not be needed for most libraries). You’ll also notice we set a version, which comes from the version defined for the given library in our package.json file. This is important because anytime we update a library, that version will dynamically change. Libraries only get shared if they have a compatible version. You can read more about these properties here.

If we spin up the application and investigate the network traffic with a focus on the react library, we’ll see that only one file gets loaded in and it comes from port 3000 (our Host application). This is a result of defining react in the shared property:

Now let’s take a look at a vendor library that hasn’t been shared yet, called @styled-system/theme-get. If we investigate our network traffic, we’ll discover that this library gets embedded into a vendor file for each micro-app. The three files highlighted below come from each of the micro-apps. You can imagine that as your libraries grow, the size of these vendor files may get quite large, and it would be better if we could share these libraries.

We will now add this library to the shared property:

If we investigate the network traffic again and search for this library, we’ll see it has been split into its own file. In this case, the Host application (which loads before everything else) loads in the library first (we know this since the file is coming from port 3000). When the other applications load in, they determine that they don’t have to use their own version of this library since it’s already been loaded in.

This very significant feature of module federation is critical for an architecture like this to succeed from a performance perspective.

Summary

Sharing code is one of the most important aspects of using module federation. Without this mechanism in place, your application would suffer from performance issues as your customers pull down a lot of duplicate code each time they accessed a different micro-app. Using the approaches above, you can ensure that your micro-apps are both independent but also capable of sharing code between themselves when appropriate. This the best of the both worlds, and is what allows a micro-frontend architecture to succeed. Now that you understand how vendor libraries are shared, we can take the same principles and apply them to our self-created libraries that live in the libs directory, which we discuss in the next article of the series.


6. Module Federation — Sharing Vendor Code was originally published in Tenable TechBlog on Medium, where people are continuing the conversation by highlighting and responding to this story.

7. Module Federation — Sharing Library Code

16 December 2021 at 18:44

Module Federation — Sharing Library Code

This is post 7 of 9 in the series

  1. Introduction
  2. Why We Implemented a Micro Frontend
  3. Introducing the Monorepo & NX
  4. Introducing Module Federation
  5. Module Federation — Managing Your Micro-Apps
  6. Module Federation — Sharing Vendor Code
  7. Module Federation — Sharing Library Code
  8. Building & Deploying
  9. Summary

Overview

This article focuses on the importance of sharing your custom library code between applications and some related best practices.

The Problem

As discussed in the previous article, sharing code is critical to using module federation successfully. In the last article we focused on sharing vendor code. Now, we want to take those same principles and apply them to the custom library code we have living in the libs directory. As illustrated below, App A and B both use Lib 1. When these micro-apps are built, they each contain a version of that library within their build artifact.

Assuming you read the previous article, you now know why this is important. As shown in the diagram below, when App A is loaded in, it pulls down all the libraries shown. When App B is loaded in it’s going to do the same thing. The problem is once again that App B is pulling down duplicate libraries that App A has already loaded in.

The Solution

Similar to the vendor libraries approach, we need to tell module federation that we would like to share these custom libraries. This way once we load in App B, it’s first going to check and see what App A has already loaded and leverage any libraries it can. If it needs a library that hasn’t been loaded in yet (or the version it needs isn’t compatible with the version App A loaded in), then it will proceed to load on its own. Otherwise, if it’s the only micro-app using that library, it will simply bundle a version of that library within itself (ex. Lib 2).

Diving Deeper

Before You Proceed: The remainder of this article is very technical in nature and is geared towards engineers who wish to learn more about sharing custom library code between your micro-apps. If you wish to see the code associated with the following section, you can check it out in this branch.

To demonstrate sharing libraries, we’re going to focus on Test Component 1 that is imported by the Host and Application 1:

This particular component lives in the design-system/components workspace:

We leverage the tsconfig.base.json file to build out our aliases dynamically based on the component paths defined in that file. This is an easy way to ensure that as new paths are added to your libraries, they are automatically picked up by webpack:

The aliases in our webpack.config are built dynamically based off the paths in the tsconfig.base.json file

How does webpack currently treat this library code? If we were to investigate the network traffic before sharing anything, we would see that the code for this component is embedded in two separate files specific to both Host and Application 1 (the code specific to Host is shown below as an example). At this point the code is not shared in any way and each application simply pulls the library code from its own bundle.

As your application grows, so does the amount of code you share. At a certain point, it becomes a performance issue when each application pulls in its own unique library code. We’re now going to update the shared property of the ModuleFederationPlugin to include these custom libraries.

Sharing our libraries is similar to the vendor libraries discussed in the previous article. However, the mechanism of defining a version is different. With vendor libraries, we were able to rely on the versions defined in the package.json file. For our custom libraries, we don’t have this concept (though you could technically introduce something like that if you wanted). To solve this problem, we decided to use a unique identifier to identify the library version. Specifically, when we build a particular library, we actually look at the folder containing the library and generate a unique hash based off of the contents of the directory. This way, if the contents of the folder change, then the version does as well. By doing this, we can ensure micro-apps will only share custom libraries if the contents of the library match.

We leverage the hashElement method from folder-hash library to create our hash ID
Each lib now has a unique version based on the hash ID generated

Note: We are once again leveraging the tsconfig.base.json to dynamically build out the libs that should be shared. We used a similar approach above for building out our aliases.

If we investigate the network traffic again and look for libs_design-system_components (webpack’s filename for the import from @microfrontend-demo/design-system/components), we can see that this particular library has now been split into its own individual file. Furthermore, only one version gets loaded by the Host application (port 3000). This indicates that we are now sharing the code from @microfrontend-demo/design-system/components between the micro-apps.

Going More Granular

Before You Proceed: If you wish to see the code associated with the following section, you can check it out in this branch.

Currently, when we import one of the test components, it comes from the index file shown below. This means the code for all three of these components gets bundled together into one file shown above as “libs_design-system_components_src_index…”.

Imagine that we continue to add more components:

You may get to a certain point where you think it would be beneficial to not bundle these files together into one big file. Instead, you want to import each individual component. Since the alias configuration in webpack is already leveraging the paths in the tsconfig.base.json file to build out these aliases dynamically (discussed above), we can simply update that file and provide all the specific paths to each component:

We can now import each one of these individual components:

If we investigate our network traffic, we can see that each one of those imports gets broken out into its own individual file:

This approach has several pros and cons that we discovered along the way:

Pros

  • Less Code To Pull Down — By making each individual component a direct import and by listing the component in the shared array of the ModuleFederationPlugin, we ensure that the micro-apps share as much library code as possible.
  • Only The Code That Is Needed Is Used — If a micro-app only needs to use one or two of the components in a library, they aren’t penalized by having to import a large bundle containing more than they need.

Cons

  • Performance — Bundling, the process of taking a number of separate files and consolidating them into one larger file, is a really good thing. If you continue down the granular path for everything in your libraries, you may very well find yourself in a scenario where you are importing hundreds of files in the browser. When it comes to browser performance and caching, there’s a balance to loading a lot of small granular files versus a few larger ones that have been bundled.

We recommend you choose the solution that works best based on your codebase. For some applications, going granular is an ideal solution and leads to the best performance in your application. However, for another application this could be a very bad decision, and your customers could end up having to pull down a ton of granular files when it would have made more sense to only have them pull down one larger file. So as we did, you’ll want to do your own performance analysis and use that as the basis for your approach.

Pitfalls

When it came to the code in our libs directory, we discovered two important things along the way that you should be aware of.

Hybrid Sharing Leads To Bloat — When we first started using module federation, we had a library called tenable.io/common. This was a relic from our initial architecture and essentially housed all the shared code that our various applications used. Since this was originally a directory (and not a library), our imports from it varied quite a bit. As shown below, at times we imported from the main index file of tenable-io/common (tenable-io/common.js), but in other instances we imported from sub directories (ex. tenable-io/common/component.js) and even specific files (tenable-io/component/component1.js). To avoid updating all of these import statements to use a consistent approach (ex. only importing from the index of tenable-io/common), we opted to expose every single file in this directory and shared it via module federation.

To demonstrate why this was a bad idea, we’ll walk through each of these import types: starting from the most global in nature (importing the main index file) and moving towards the most granular (importing a specific file). As shown below, the application begins by importing the main index file which exposes everything in tenable-io/common. This means that when webpack bundles everything together, one large file is created for this import statement that contains everything (we’ll call it common.js).

We then move down a level in our import statements and import from subdirectories within tenable-io/common (components and utilities). Similar to our main index file, these import statements contain everything within their directories. Can you see the problem? This code is already contained in the common.js file above. We now have bloat in our system that causes the customer to pull down more javascript than necessary.

We now get to the most granular import statement where we’re importing from a specific file. At this point, we have a lot of bloat in our system as these individual files are already contained within both import types above.

As you can imagine, this can have a dramatic impact on the performance of your application. For us, this was evident in our application early on and it was not until we did a thorough performance analysis that we discovered the culprit. We highly recommend you evaluate the structure of your libraries and determine what’s going to work best for you.

Sharing State/Storage/Theme — While we tried to keep our micro-apps as independent of one another as possible, we did have instances where we needed them to share state and theming. Typically, shared code lives in an actual file (some-file.js) that resides within a micro-app’s bundle. For example, let’s say we have a notifications library shared between the micro-apps. In the first update, the presentation portion of this library is updated. However, only App B gets deployed to production with the new code. In this case, that’s okay because the code is constrained to an actual file. In this instance, App A and B will use their own versions within each of their bundles. As a result, they can both operate independently without bugs.

However, when it comes to things like state (Redux for us), storage (window.storage, document.cookies, etc.) and theming (styled-components for us), you cannot rely on this. This is because these items live in memory and are shared at a global level, which means you can’t rely on them being confined to a physical file. To demonstrate this, let’s say that we’ve made a change to the way state is getting stored and accessed. Specifically, we went from storing our notifications under an object called notices to storing them under notifications. In this instance, once our applications get out of sync on production (i.e. they’re not leveraging the same version of shared code where this change was made), the applications will attempt to store and access notifications in memory in two different ways. If you are looking to create challenging bugs, this is a great way to do it.

As we soon discovered, most of our bugs/issues resulting from this new architecture came as a result of updating one of these areas (state, theme, storage) and allowing the micro-apps to deploy at their own pace. In these instances, we needed to ensure that all the micro-apps were deployed at the same time to ensure the applications and the state, store, and theming were all in sync. You can read more about how we handled this via a Jenkins bootstrapper job in the next article.

Summary

At this point you should have a fairly good grasp on how both vendor libraries and custom libraries are shared in the module federation system. See the next article in the series to learn how we build and deploy our application.


7. Module Federation — Sharing Library Code was originally published in Tenable TechBlog on Medium, where people are continuing the conversation by highlighting and responding to this story.

8. Building & Deploying

16 December 2021 at 18:45

Building & Deploying

This is post 8 of 9 in the series

  1. Introduction
  2. Why We Implemented a Micro Frontend
  3. Introducing the Monorepo & NX
  4. Introducing Module Federation
  5. Module Federation — Managing Your Micro-Apps
  6. Module Federation — Sharing Vendor Code
  7. Module Federation — Sharing Library Code
  8. Building & Deploying
  9. Summary

Overview

This article documents the final phase of our new architecture where we build and deploy our application utilizing our new micro-frontend model.

The Problem

If you have followed along up until this point, you can see how we started with a relatively simple architecture. Like a lot of companies, our build and deployment flow looked something like this:

  1. An engineer merges their code to master.
  2. A Jenkins build is triggered that lints, tests, and builds the entire application.
  3. The built application is then deployed to a QA environment.
  4. End-2-End (E2E) tests are run against the QA environment.
  5. The application is deployed to production. If it’s a CICD flow this occurs automatically if E2E tests pass, otherwise this would be a manual deployment.

In our new flow this would no longer work. In fact, one of our biggest challenges in implementing this new architecture was in setting up the build and deployment process to transition from a single build (as demonstrated above) to multiple applications and libraries.

The Solution

Our new solution involved three primary Jenkins jobs:

  1. Seed Job — Responsible for identifying what applications/libraries needed to be rebuilt (via the nx affected command). Once this was determined, its primary purpose was to then kick off n+ of the next two jobs discussed.
  2. Library Job — Responsible for linting and testing any library workspace that was impacted by a change.
  3. Micro-App Jobs — A series of jobs pertaining to each micro-app. Responsible for linting, testing, building, and deploying the micro-app.

With this understanding in place, let’s walk through the steps of the new flow:

Phase 1 — In our new flow, phase 1 includes building and deploying the code to our QA environments where it can be properly tested and viewed by our various internal stakeholders (engineers, quality assurance, etc.):

  1. An engineer merges their code to master. In the diagram below, an engineer on Team 3 merges some code that updates something in their application (Application C).
  2. The Jenkins seed job is triggered, and it identifies what applications and libraries were impacted by this change. This job now kicks off an entirely independent pipeline related to the updated application. In this case, it kicked off the Application C pipeline in Jenkins.
  3. The pipeline now lints, tests, and builds Application C. It’s important to note here how it’s only dealing with a piece of the overall application. This greatly improves the overall build times and avoids long queues of builds waiting to run.
  4. The built application is then deployed to the QA environments.
  5. End-2-End (E2E) tests are run against the QA environments.
  6. Our deployment is now complete. For our purposes, we felt that a manual deployment to production was a safe approach for us and one that still offered us the flexibility and efficiency we needed.
Phase 1 Highlighted — Deploying to QA environments

Phase 2 — This phase (shown in the diagram after the dotted line) occurred when an engineer was ready to deploy their code to production:

  1. An engineer deployed their given micro-app to staging. In this case, the engineer would go into the build for Application C and deploy from there.
  2. For our purposes, we deployed to a staging environment before production to perform a final spot check on our application. In this type of architecture, you may only encounter a bug related to the decoupled nature of your micro-apps. You can read more about this type of issue in the previous article under the Sharing State/Storage/Theme section. This final staging environment allowed us to catch these issues before they made their way to production.
  3. The application is then deployed to production.
Phase 2 Highlighted — Deploying to production environments

While this flow has more steps than our original one, we found that the pros outweigh the cons. Our builds are now more efficient as they can occur in parallel and only have to deal with a specific part of the repository. Additionally, our teams can now move at their own pace, deploying to production when they see fit.

Diving Deeper

Before You Proceed: The remainder of this article is very technical in nature and is geared towards engineers who wish to learn the specifics of how we build and deploy our applications.

Build Strategy

We will now discuss the three job types discussed above in more detail. These include the following: seed job, library job, and micro-app jobs.

The Seed Job

This job is responsible for first identifying what applications/libraries needed to be rebuilt. How is this done? We will now come full circle and understand the importance of introducing the NX framework that we discussed in a previous article. By taking advantage of this framework, we created a system by which we could identify which applications and libraries (our “workspaces”) were impacted by a given change in the system (via the nx affected command). Leveraging this functionality, the build logic was updated to include a Jenkins seed job. A seed job is a normal Jenkins job that runs a Job DSL script and in turn, the script contains instructions that create and trigger additional jobs. In our case, this included micro-app jobs and/or a library job which we’ll discuss in detail later.

Jenkins Status — An important aspect of the seed job is to provide a visualization for all the jobs it kicks off. All the triggered application jobs are shown in one place along with their status:

  • Green — Successful build
  • Yellow — Unstable
  • Blue — Still processing
  • Red (not shown) — Failed build

Github Status — Since multiple independent Jenkins builds are triggered for the same commit ID, we had to pay attention to the representation of the changes in GitHub to not lose visibility of broken builds in the PR process. Each job registers itself with a unique context with respect to github, providing feedback on what sub-job failed directly in the PR process:

Performance, Managing Dependencies — Before a given micro-app and/or library job can perform its necessary steps (lint, test, build), it needs to install the necessary dependencies for those actions (those defined in the package.json file of the project). Doing this every single time a job is run is very costly in terms of resources and performance. Since all of these jobs need the same dependencies, it makes much more sense if we can perform this action once so that all the jobs can leverage the same set of dependencies.

To accomplish this, the node execution environment was dockerised with all necessary dependencies installed inside a container. As shown below, the seed job maintains the responsibility for keeping this container in sync with the required dependencies. The seed job determines if a new container is required by checking if changes have been made to package.json. If changes are made, the seed job generates the new container prior to continuing any further analysis and/or build steps. The jobs that are kicked off by the seed (micro-app jobs and the library job) can then leverage that container for use:

This approach led to the following benefits:

  • Proved to be much faster than downloading all development dependencies for each build (step) every time needed.
  • The use of a pre-populated container reduced the load on the internal Nexus repository manager as well as the network traffic.
  • Allowed us to run the various build steps (lint, unit test, package) in parallel thus further improving the build times.

Performance, Limiting The Number Of Builds Run At Once — To facilitate the smooth operation of the system, the seed jobs on master and feature branch builds use slightly different logic with respect to the number of builds that can be kicked off at any one time. This is necessary as we have a large number of active development branches and triggering excessive jobs can lead to resource shortages, especially with required agents. When it comes to the concurrency of execution, the differences between the two are:

  • Master branch — Commits immediately trigger all builds concurrently.
  • Feature branches — Allow only one seed job per branch to avoid system overload as every commit could trigger 10+ sub jobs depending on the location of the changes.

Another attempt to reduce the amount of builds generated is the way in which the nx affected command gets used by the master branch versus the feature branches:

  • Master branch — Will be called against the latest tag created for each application build. Each master / production build produces a tag of the form APP<uniqueAppId>_<buildversion>. This is used to determine if the specific application needs to be rebuilt based on the changes.
  • Feature branches — We use master as a reference for the first build on the feature branch, and any subsequent build will use the commit-id of the last successful build on that branch. This way, we are not constantly rebuilding all applications that may be affected by a diff against master, but only the applications that are changed by the commit.

To summarize the role of the seed job, the diagram below showcases the logical steps it takes to accomplish the tasks discussed above.

The Library Job

We will now dive into the jobs that Seed kicks off, starting with the library job. As discussed in our previous articles, our applications share code from a libs directory in our repository.

Before we go further, it’s important to understand how library code gets built and deployed. When a micro-app is built (ex. nx build host), its deployment package contains not only the application code but also all the libraries that it depends on. When we build the Host and Application 1, it creates a number of files starting with “libs_…” and “node_modules…”. This demonstrates how all the shared code (both vendor libraries and your own custom libraries) needed by a micro-app is packaged within (i.e. the micro-apps are self-reliant). While it may look like your given micro-app is extremely bloated in terms of the number of files it contains, keep in mind that a lot of those files may not actually get leveraged if the micro-apps are sharing things appropriately.

This means building the actual library code is a part of each micro-app’s build step, which is discussed below. However, if library code is changed, we still need a way to lint and test that code. If you kicked off 5 micro-app jobs, you would not want each of those jobs to perform this action as they would all be linting and testing the exact same thing. Our solution to this was to have a separate Jenkins job just for our library code, as follows:

  1. Using the nx affected:libs command, we determine which library workspaces were impacted by the change in question.
  2. Our library job then lints/tests those workspaces. In parallel, our micro-apps also lint, test and build themselves.
  3. Before a micro-app can finish its job, it checks the status of the libs build. As long as the libs build was successful, it proceeds as normal. Otherwise, all micro-apps fail as well.

The Micro-App Jobs

Now that you understand how the seed and library jobs work, let’s get into the last job type: the micro-app jobs.

Configuration — As discussed previously, each micro-app has its own Jenkins build. The build logic for each application is implemented in a micro-app specific Jenkinsfile that is loaded at runtime for the application in question. The pattern for these small snippets of code looks something like the following:

The jenkins/Jenkinsfile.template (leveraged by each micro-app) defines the general build logic for a micro-application. The default configuration in that file can then be overwritten by the micro-app:

This approach allows all our build logic to be in a single place, while easily allowing us to add more micro-apps and scale accordingly. This combined with the job DSL makes adding a new application to the build / deployment logic a straightforward and easy to follow process.

Managing Parallel Jobs — When we first implemented the build logic for the jobs, we attempted to implement as many steps as possible in parallel to make the builds as fast as possible, which you can see in the Jenkins parallel step below:

After some testing, we found that linting + building the application together takes about as much time as running the unit tests for a given product. As a result, we combined the two steps (linting, building) into one (assets-build) to optimize the performance of our build. We highly recommend you do your own analysis, as this will vary per application.

Deployment strategy

Now that you understand how the build logic works in Jenkins, let’s see how things actually get deployed.

Checkpoints — When an engineer is ready to deploy their given micro-app to production, they use a checkpoint. Upon clicking into the build they wish to deploy, they select the checkpoints option. As discussed in our initial flow diagram, we force our engineers to first deploy to our staging environment for a final round of testing before they deploy their application to production.

The particular build in Jenkins that we wish to deploy
The details of the job above where we have the ability to deploy to staging via a checkpoint

Once approval is granted, the engineer can then deploy the micro-app to production using another checkpoint:

The build in Jenkins that was created after we clicked deployToQAStaging
The details of the job above where we have the ability to deploy to production via a checkpoint

S3 Strategy — The new logic required a rework of the whole deployment strategy as well. In our old architecture, the application was deployed as a whole to a new S3 location and then the central gateway application was informed of the new location. This forced the clients to reload the entire application as a whole.

Our new strategy reduces the deployment impact to the customer by only updating the code on S3 that actually changed. This way, whenever a customer pulls down the code for the application, they are pulling a majority of the code from their browser cache and only updated files have to be brought down from S3.

One thing we had to be careful about was ensuring the index.html file is only updated after all the granular files are pushed to S3. Otherwise, we run the risk of our updated application requesting files that may not have made their way to S3 yet.

Bootstrapper Job — As discussed above, micro-apps are typically deployed to an environment via an individual Jenkins job:

However, we ran into a number of instances where we needed to deploy all micro-apps at the same time. This included the following scenarios:

  • Shared state — While we tried to keep our micro-apps as independent of one another as possible, we did have instances where we needed them to share state. When we made updates to these areas, we could encounter bugs when the apps got out of sync.
  • Shared theme — Since we also had a global theme that all micro-apps inherited from, we could encounter styling issues when the theme was updated and apps got out of sync.
  • Vendor Library Update — Updating a vendor library like react where there could be only one version of the library loaded in.

To address these issues, we created the bootstrapper job. This job has two steps:

  1. Build — The job is run against a specific environment (qa-development, qa-staging, etc.) and pulls down a completely compiled version of the entire application.
  2. Deploy — The artifact from the build step can then be deployed to the specified environment.

Conclusion

Our new build and deployment flow was the final piece of our new architecture. Once it was in place, we were able to successfully deploy individual micro-apps to our various environments in a reliable and efficient manner. This was the final phase of our new architecture, please see the last article in this series for a quick recap of everything we learned.


8. Building & Deploying was originally published in Tenable TechBlog on Medium, where people are continuing the conversation by highlighting and responding to this story.

9. Wrapping Up Our Journey Implementing a Micro Frontend

16 December 2021 at 18:46

Wrapping Up Our Journey Implementing a Micro Frontend

We hope you now have a better understanding of how you can successfully create a micro-front end architecture. Before we call it a day, let’s give a quick recap of what was covered.

What You Learned

  • Why We implemented a micro front end architecture — You learned where we started, specifically what our architecture used to look like and where the problems existed. You then learned how we planned on solving those problems with a new architecture.
  • Introducing the Monorepo and NX — You learned how we combined two of our repositories into one: a monorepo. You then saw how we leveraged the NX framework to identify which part of the repository changed, so we only needed to rebuild that portion.
  • Introducing Module Federation — You learned how we leverage webpacks module federation to break our main application into a series of smaller applications called micro-apps, the purpose of which was to build and deploy these applications independently of one another.
  • Module Federation — Managing Your Micro-Apps — You learned how we consolidated configurations and logic pertaining to our micro-apps so we could easily manage and serve them as our codebase continued to grow.
  • Module Federation — Sharing Vendor Code — You learned the importance of sharing vendor library code between applications and some related best practices.
  • Module Federation — Sharing Library Code — You learned the importance of sharing custom library code between applications and some related best practices.
  • Building and Deploying — You learned how we build and deploy our application using this new model.

Key Takeaways

If you take anything away from this series, let it be the following:

The Earlier, The Better

We can tell you from experience that implementing an architecture like this is much easier if you have the opportunity to start from scratch. If you are lucky enough to start from scratch when building out an application and are interested in a micro-frontend, laying the foundation before anything else is going to make your development experience much better.

Evaluate Before You Act

Before you decide on an architecture like this, make sure it’s really what you want. Take the time to assess your issues and how your company operates. Without company support, pulling off this approach is extremely difficult.

Only Build What Changed

Using a tool like NX is critical to a monorepo, allowing you to only rebuild those parts of the system that were impacted by a change.

Micro-front Ends Are Not For Everyone

We know this type of architecture is not for everyone, and you should truly consider what your organization needs before going down this path. However, it has been very rewarding for us, and has truly transformed how we deliver solutions to our customers.

Don’t Forget To Share

When it comes to module federation, sharing is key. Learning when and how to share code is critical to the successful implementation of this architecture.

Be Careful Of What You Share

Sharing things like state between your micro-apps is a dangerous thing in a micro-frontend architecture. Learning to put safeguards in place around these areas is critical, as well as knowing when it might be necessary to deploy all your applications at once.

Summary

We hope you enjoyed this series and learned a thing or two about the power of NX and module federation. If this article can help just one engineer avoid a mistake we made, then we’ll have done our job. Happy coding!


9. Wrapping Up Our Journey Implementing a Micro Frontend was originally published in Tenable TechBlog on Medium, where people are continuing the conversation by highlighting and responding to this story.

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