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What’s so cool about micro frontends?

11 July, 2019 | 25 min 14 sec
Podcast Host Rebecca Parsons | Podcast Guest Cam Jackson
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Brief Summary

Rebecca Parsons and Cam Jackson, a senior consultant at ThoughtWorks Australia explore the trend of breaking up a web application into decoupled micro frontends, and how such an architecture can improve delivery quality and efficiency for the teams working on frontend code.

Podcast Transcript


Rebecca Parsons:

Hello. My name is Rebecca Parsons. I am here today for the ThoughtWorks podcast and I'm speaking to Cam Jackson and we're going to discuss micro frontends. Welcome Cam.


Cam Jackson:

Thanks for having me.


Rebecca Parsons:

Tell us a little bit about yourself and how you got involved in frontend technology and micro frontends in particular.


Cam Jackson:

Sure. So I'm a developer here with ThoughtWorks. I've been working as a consultant for about five years, a little over five years. I didn't join as a frontend developer, just as a developer consultant. My first project was actually very infrastructure focused, so no frontend work at all. And then I sort of just fell into doing frontend work over the years and that's where I've spent most of my time doing. And I certainly enjoy it. But you know, I really think of myself as a full stack dev. But yeah, probably what I've spent most of my time focusing on is the frontend world. And I guess the work that I'm most interested in and proudest of is helping large organizations to scale their frontends development processes and practices across many teams and across some really complex products.


Rebecca Parsons:

Great. So what is a micro frontend? I mean everybody's talking about microservices. Is it just microservice ish stuff applied to frontends? What does it really look like?


Cam Jackson:

There's certainly a lot of parallels to microservices. So I sometimes start by talking about that because that's what more people are familiar with. I can give you a sort of a dictionary definition, that I use, which is that micro frontends is an architectural style where independently deliverable frontend applications are composed into a greater whole. So there's a couple of things in there. There's the composition part of it, which is probably not that exciting. I mean most UIs are being built using composition as the main sort of pattern for putting things together. Probably the more interesting part is that independently deliverable bit. So we usually end up with something like each micro frontend is maybe a page in part of a greater product or maybe there might even be several micro frontends on the one page.


Cam Jackson:

But the important thing is that each one of those micro frontends should be end to end independently deliverable. So that usually looks like each micro friend has its own source code repository. It's got its own set of dependencies. It's own automated test suite and a delivery pipeline that takes it all the way to production and it's probably owned by a single team. So that's pretty powerful. What we usually end up seeing there is if we need to add a new feature to our product, a single team can pick up that feature and take it from analysis all the way through to production on their own. Nice and autonomous and independent from all the other teams and without having to do lots of coordination.


Rebecca Parsons:

And is there something in the overall architecture of the application that enables that level of separation? I mean, do you require a particular frontend to backend style architecture to really make this work?


Cam Jackson:

I think the main thing is making sure that if you're drawing boundaries within your application in terms of I guess where the seams are, they definitely need to be very business oriented and feature oriented. If you've built teams around kind of bounded contexts and domain concepts, it works really well. So you know if you've got a products page and your application having a products team that owns that page, that works really well and it works even better if they also own the backend part of the stack because it means again they can go end to end full stack features all the way to production without having to wait on other teams to do stuff for them.


Rebecca Parsons:

And it's amazing how often people think that it's so much more efficient to have those, you know, frontend technology team in this back end technology team and then you have to coordinate all those teams to get anything into production.


Cam Jackson:

Yeah, definitely. And I also try to steer people away from even just within the frontend space having I guess horizontal teams that focus on things like having a styling team or a forms team or a validation team. Like those shouldn't be teams. There should just be things that each one of your product teams has to do.


Rebecca Parsons:

Even if there's a certain level of consistency, you're trying to maintain a consistent style that doesn't mean you need a team to maintain a consistent style. So what are the problems that are actually addressed through micro frontends?


Cam Jackson:

I guess the one that we've already been talking about is team autonomy. So particularly in larger organizations that's where I see this pattern happening the most. There's a lot of coordination that ends up happening between teams. For one team to put a feature into production they've got to work with lots of other teams. They've got to coordinate their release processes, talk about who owns which piece of code. Micro frontends tries to avoid all of that by saying each feature should live just within a micro frontend and you don't have to coordinate with anybody else to put it into production. So that's probably the biggest one which comes up front. You then see a little bit deeper at the technical level. You can sort of detangle the various parts of your application or your product. When all of the code for a product is located altogether and you've got maybe a hundred developers all working on the one product, you always get this kind of accidental entanglement or coupling that happens across different parts of the application.


Cam Jackson:

No one really intended for this section over here to be related to this other section, they shouldn't really have any common code, but somehow they just always end up with some shared global state or some module that they both depend on. It now becomes really difficult to make changes to one without having to make changes to the other as well. So microphones kind of help us to draw I guess thicker boundaries around different parts of our product and say when I work on this part of it, I shouldn't need to look at this part over here.


Cam Jackson:

The other one that comes up, and actually a lot of people sort of accidentally fall into doing something like micro frontends is when you're trying to do incremental upgrades of your tech stack. So we see this all the time, it's probably a pretty familiar story to people, you've got your frontend which was built in an old technology and it's a huge monolith that might be all done in backbone JS, maybe it's an angular 1.0 thing, which has been around for a while, and it's old tech and nobody really wants to work on it and no one really understands it anymore because everyone's moved on since it was first built. So we want to do an upgrade, we want to do a migration from that to some newer technology, which is nicer to work with.


Cam Jackson:

Now obviously what we want to avoid is stopping all feature development so we can rewrite the entire thing, that very rarely works out. So we want to find ways to incrementally upgrade it. I guess the strangler pattern is a pattern that people often talk about on the back end side of things where we're able to just gradually extract out piece by piece and rewrite or replace small parts of the application until eventually there's nothing left of the old thing. I think people have been doing that for a long time on backend code, but it hasn't been done so much on frontend code. So you often see people saying, well I've got this big angular 1.0 thing, I'm going to take just one page because that's the page I need to work on right now and as I add new features to it, I'm going to rewrite it in react for example. If you do that several times very quickly, you've accidentally implemented micro frontends just by doing that. I see a lot of people getting into micro frontends just because they're trying to do an upgrade of their tech stack.


Rebecca Parsons:

So one of the critical design decisions when you talk about microservices is that domain or that boundary around the microservice. From a business domain, from a bounded context perspective, how you draw those boundaries is critical. Do you think that this accidental falling into a micro frontend architecture, how good are those boundary choices? I mean when you look at it dispassionately, are those sensible boundaries? I mean you, you could make the argument that since that's kind of the way it was designed before because they were pages, it's probably not so bad, but what's your sense about that?


Cam Jackson:

Yeah, I think you're right. I think it tends to work out really well. I think there's a lot to be said for designing our code in the way that our users would think of it. If we have the mental model from a technical point of view of how our application works, if it matches with how our users think the software should work or what the different sections of the application are, I think that usually goes pretty well. Definitely I think there's almost doing it in the frontend space is easier to draw those boundaries because you just look at the application in your web browser and say well that page there, that looks like a micro frontend, let's split that out and I think that applies to frontend code in general. I'm trying to figure out what should be a component and what things should compose together. You can often just look at the design and if you just draw boxes around the different parts of the page that serves you pretty well I think for figuring out how to divide up your code as well.


Rebecca Parsons:

Are micro frontends new or is this just something that we've figured out a name for?


Cam Jackson:

Yeah, I think it's not particularly new. When I first started trying to write about micro frontends, I sat down with Evan [inaudible] to get his inputs on it and one of the things he said is, "I feel like I was doing this 15 years ago and we were just doing everything was rented from templates on the server and we just did server-side includes. The page was composed together out of all these HTML static fragments on the service side and each one of those fragments was owned by a team. Is that micro frontends?" Initially I sort of thought, no, no, no, that can't be micro frontends. That's old school. But when I started to actually think about all the benefits and what the important attributes of micro frontends are, I couldn't really think of a reason why it's not micro frontends.


Cam Jackson:

So I gradually came round to, yeah, it doesn't matter what the technology is and yeah, it's not necessarily a new pattern. I do think it's helpful to give names to things, even if we've been doing them for a while. I would say that I think there's a renewed focus on these kinds of patterns because web applications are only getting more and more complex and they're getting bigger. I think as user experiences get more, it's more important to have a really solid user experience in your product. So we often see more code getting pushed to the frontend than we used to have. That means we've just got more frontend code to manage and so it becomes more difficult to manage the complexity in that because as things get bigger they get more complicated. So there is a renewed focus I think, in finding ways to divide up our products into these independent frontend pieces that can be worked on by teams independently of each other.


Rebecca Parsons:

So if we were doing this 15 years ago, or at least Evan was, where did we go wrong? Do you think there was some kind of dynamic that pushed us away from thinking about our user facing applications in that way? To these monoliths, which apparently we adore when we're not despising them.


Cam Jackson:

Yeah. I think part of that is traditionally frontend development. It sort of been seen as a bit of a lesser form of development by some people. That's certainly not what I've ever thought. Especially the first time I tried to do it, I realized, wow, this is really hard. And I suddenly had a lot more respect for the people who actually do it. So I think, yeah, maybe partly why we haven't been as good at this is we haven't given it the attention it deserves. And I think people who have are probably the people who've been doing this for a while and are going to say, so what I've always been dividing up my frontend code into these nicely segmented pieces, but maybe a lot of other people have not been treating frontend code as you know, real proper code that deserves attention and deserve some thought into its architecture so that's now something that I think more people are trying to do.


Rebecca Parsons:

The radar for the win once again. Several years ago we said treat JavaScript as a first class citizen. We need to think about engineering practices, design practices, all of those things in the same way, even if it's just frontend codes. So why did you choose to write about it now?


Cam Jackson:

Well, I chose to write about it a couple of years ago. I mean-


Rebecca Parsons:

I know how that goes.


Cam Jackson:

Anybody who's tried to write a long article or even a short article probably knows that it takes a lot longer than you think. It was a couple of years ago, mostly just because that's what I was spending most of my days doing and I was looking around me and seeing people who were doing something like this pattern were having a really good time with it and people who were not, some of them are doing really well, but a lot of them were really struggling. And so I saw almost everywhere I went, several clients in a row, there was a similar story. Oh we've got this big old frontend thing and it's really hard to work on and we're all stepping on each other's toes. We want to find ways to split it up. So it just seems to be a common theme that was popping up everywhere I went. And so I thought maybe this thing needs a name and maybe we need to sit down and as I guess as a profession, talk more about how we're doing this and how we can do it better.


Rebecca Parsons:

So one of the things about microservices, and I do see a lot of parallels really between microservices and what we're talking about here. Martin has the article, you have to be this tall to be able to do microservices. So there are clearly times when it's just not worth paying the cost. Do you feel the same way about micro frontend?


Cam Jackson:

Yeah, for sure. After writing my article though a lot of people were sort of saying this seems way too complicated, why would you do that? For sure there are times where the benefits that you get don't outweigh the extra complexity because there is a bit more complexity in doing things this way. If you are a one person company or even if you're a one team company, there's probably not much point in trying to do something like this. I mean as long as you are thinking about where the seams in your application are and I guess where the boundaries are between different things, it's pretty easy to start pulling things out later on. If your needs are small and simple, it's probably not worth it. I guess the other way of phrasing that is if you don't have the problems that micro frontends are supposed to solve, then there's probably not much point in it. If you're not trying to scale an organization to a hundred people working on the same product, if you're finding that you don't really have problems with lots of coupling in your monolith code base, and if you're not trying to move from one tech stack to another, there's probably not that much benefit in doing it.


Rebecca Parsons:

What is the source of the complexity? I mean it's pretty clear in the microservices world you've got all kinds of errors, for example, that just can't happen if you've got a monolith. Are there similar parallels or is the source of complexity different when you think about micro frontends?


Cam Jackson:

I think there's a couple of sources of complexity. Frontend code is a bit different in that even if we're trying to slice things up from a technical point of view, users still need to see a single application. Users shouldn't know the different pages in the app are deployed independently. It should feel like a single cohesive app or a single product. So that's probably where a lot of the complexity comes is saying, well we've got these five different teams working on one product, and they're meant to be independent from each other, how do we make sure that what they end up producing looks like a single product?


Cam Jackson:

So there are a bunch of things you can do with that. Having a well-documented design system or a shared library of reusable UI components, that goes a long way to making sure everyone's doing the same thing and just having people talk to each other. I mean, just because our teams are independent and they don't have to coordinate, it doesn't mean that they shouldn't collaborate. So you still want people talking to each other. You still want people saying, "Hey, I solved this problem already there's no need for you to solve it again", that's always something that we should be doing. And I think, I guess that's where the technical leadership becomes really important, to have people who are bringing those teams together to make sure they're all moving in the same direction.


Rebecca Parsons:

It also seems to me when I think about how microservices tend to be encapsulated and communicate with each other and then you think about it from the frontend perspective, particularly in the case where you have multiple micro frontends on a page. As a user, I expect all of those things to know about each other so that if I type something in one place, I type my zip code in over here, the little FedEx search box knows what my zip code is. Is that something that introduces additional complexity? How am I actually going to share this context across these multiple frontends when I still want them to be able to be deployed independently?


Cam Jackson:

Yeah, definitely. I mean integration is always the hardest thing, right?


Rebecca Parsons:

Absolutely. That's what makes it fun.


Cam Jackson:

Right. So figuring out ways for micro frontends to talk to each other or communicate or share knowledge is the hardest thing to do. Well without also making it so that we've got all that coupling that we were trying to eliminate in the first place. So I think the main thing is to be deliberate and explicit about what communication there is between micro frontends. And I think that's what we were doing wrong before is that we weren't deliberate or explicit about it. It was just everything knew about everything and that's why things were so tangled. So now that we've separated things, they still probably need to talk to each other a little bit. So if we put some thought into thinking about what is the contract here, what does this micro frontend expect of this other micro frontend, then then things are going to go a lot better.


Cam Jackson:

So you know, whether it's just using events or messages to publish something onto the page, to one micro frontend can say, "Hey, this piece of state changed and anybody else who's interested in that can listen for it and do what they need to do", that tends to work pretty well. What I usually tell people to avoid is direct state, which is shared directly across micro frontends. I mean shared, mutable state usually goes badly and I think the analogy for backend code would be having an integration database. So it's an anti-pattern that we talk about a lot is microservices that share a database because now they're completely coupled to the same domain model. You can't evolve your database or change out your models without having to change everyone all at once. So I think particularly when you look at a library like Redux for example, Redux on the frontend says there's a single global store, which is where we put shared state and everybody shares the same store, it works pretty well.


Cam Jackson:

But if you've got multiple micro frontends, I would say if you do want to use Redux, each micro frontend should have its own store. Don't share a single store across everyone because that's a great way to have a bunch of global state, which you can now never change the design of that state. You can never rename a field basically because renaming a field would require everyone to go and rename the field in their own code bases. The other thing which is I guess the complexity which is unique to the frontend side is styling and CSS collisions. And again this is not a new problem like we've been struggling with, you know two different people tried to use the same name for their CSS selector and they conflict or having specificity battles over making sure that my selector over overrides your selector.


Cam Jackson:

We've been, we've been having that problem with CSS forever, but it becomes worse when you've got multiple teams who are meant to be separate from each other. If they're all writing CSS which sits in the same scope, that's going to be a complete mess. So without getting into too many details, there are a whole bunch of different ways that you can solve that. It doesn't really matter which one you pick as long as your guiding needs to be when I'm writing some styling code and you're writing some styling code, we both need to be confident that we know what it's going to look like in the end. That mine is not going to override yours and yours isn't going to override mine.


Rebecca Parsons:

And we can continue to cheerfully ignore each other.


Cam Jackson:

Yes (laughter).


Rebecca Parsons:

Do what we need to do. Absolutely. Because that's of course one of the benefits we're trying to achieve here is to allow those teams to work in the play independently.


Cam Jackson:

Yep.


Rebecca Parsons:

So how do people go wrong when they're trying to work with micro frontends?


Cam Jackson:

I think what people struggle with sometimes is balancing this kind of a spectrum of centrally controlling and standardizing everything versus complete chaos where nobody talks to each other at all. I think both extremes of those spectrums are pretty wrong, but it's hard to find how to find the balance in the middle and different organizations will have different cultures around that sort of thing. You know, definitely if you're a startup which has grown into a big organization, there's probably more of a culture of move fast and just do whatever you want and that works well to a point, but one day you realize that, Oh my God, everyone's doing completely different things here. It's affecting the consistency of our UI. It's affecting our download sizes because we've got five different frameworks on the same page, so that's not good.


Cam Jackson:

At the other end what you sometimes see in I guess more corporate places is the desire to over standardize and over centralize. And so everybody has to do everything exactly the same way. We all have to use exactly the same versions of every single dependency. All of our build pipelines have to look the same and all of a sudden, well, you may as well have just built a monolith. If you're forcing everyone to endlessly coordinate and do things the same way and every single decision has to go to a committee, it would probably be faster to just do it in a monolith and stop pretending that you're doing micro frontends, I guess. So that's a balance which is really difficult to strike and that's probably where I spend a lot of my consulting time is trying to help people find the right balance. It would be different for each organization.


Rebecca Parsons:

Do you think it varies much by the style of application where that balance point is or is it more really organizational and cultural?


Cam Jackson:

Yeah, I think it can as well. I mean if you're building something for the general public, it's probably more important that things are really fast. So you want to put more effort into deduplicating dependencies and maybe sharing dependencies so you can reduce the number of bots. And the consistency of the user experience is absolutely paramount. If you are building, and I've seen this a few times, if you're building an internal product, which is basically just a portal into a bunch of, maybe slightly related but relatively independent little applications, it probably matters a little bit less that everything is totally consistent. And so in situation I would probably optimize more for speed of delivery and letting people do their own thing a little bit more. Because it doesn't really matter if things look slightly different in the various different internal web applications.


Rebecca Parsons:

So is there anything else you wanted to say that I didn't ask you about?


Cam Jackson:

I don't think so. I think the main thing is I really just want people to be thinking about this stuff. Like I said earlier, for a long time frontend development hasn't been seen as real development. Whether people go and do micro frontends or whether they do something completely different. It doesn't really bother me. Obviously I like working on micro frontends. That's why I'm writing about it and talking about it. But if they want to choose a completely different pattern that's awesome and I love that as long as people are actually putting the effort in, putting the thought in and treating frontend development as real development and trying to do things properly.


Rebecca Parsons:

Thank you very much. This has been the ThoughtWorks podcast and we'll see you next time.


Neal Ford:

Hi, this is Neal, one of your regular hosts. On our next episode of the podcast, we're going to talk about something that you can't even Google. This concept that comes from our colleagues in China, called Zhong Tai, you'll get the correct pronunciation in Chinese in the episode. It's an interesting way of thinking about encapsulating platforms as business models. So please join us for the next episode.

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