or, how we stopped using fastlane for continuous integration
I previously wrote about how to set up continuous integration for an iOS app with fastlane and Jenkins. I have since changed my mind about that approach.
Why we used fastlane
When I was initially tasked with setting up CI for our team, I used fastlane because
- Senior developers said “I heard about this thing called fastlane that can automate iOS deployment. You should use that.”
- and when I looked up fastlane it had a large community around it
To be fair, fastlane did work. For about a year, on every push it would build our app, run our tests, and report back to git if the branch was OK to merge. This brought huge improvements to our development process because previously we were basically relying on due diligence and the honor system to make sure that tests got run.
What sucks about fastlane
- Xcode sucks
- It’s a huge dependency
- It’s buggy
- Everyone uses it
- It’s an additional layer of complexity
- It has way 👏 too 💯 many 😂 emoji 🚀
Let’s dive into each of these a bit.
fastlane advertises itself as making your life as an iOS developer so much easier. Perhaps in certain areas that is true, but for a lot of what we were using fastlane for it was ultimately just wrapping commands to Xcode. And here’s the problem: Xcode really really sucks. A lot. I hate it.
Ever since the release of Xcode 10, some frameworks in our app sometimes have build cycles reported inside them. Somehow Xcode thinks that linking the files in a framework can require the framework itself to already be built? I have a 500 point bounty on Stackoverflow about this. Let’s not get into that. The point is that sometimes, seemingly randomly, Xcode will decide it won’t build our app anymore. That means the Jenkins build fails, which means no tests run, which means no merge.
Or sometimes the build succeeds and Xcode won’t run the tests. Why? “Early unexpected exit,” it says. “No restart will be attempted,” even though restarting the tests is literally the only fix for this error. So again, no tests, no merge, seemingly at random.
fastlane doesn’t help with this. And I don’t expect it to, because fastlane is built on the insane assumption that Xcode will always work. So this isn’t a mark against fastlane, but for us it made me start to question why we used this tool if it was doing nothing to address the two main pain points for our continuous integration setup. Especially considering that fastlane is a
When you finally get fastlane running and look at your cute little
you’ll feel giddy:
So simple! So clean! Just don’t look at your
That simplicity doesn’t come cheap. And since we want to keep our Jenkins workspaces clean, that’s 67 dependencies to install on the build machine for every push.
And it’s not just big in terms of build dependencies. fastlane does a lot at runtime that I don’t care about. For example, every one of our builds gets tons of messages like this:
Sometimes it takes three or four of these timeouts (with increasing durations) before it succeeds. Why run this at all? And when you look at the build command it ends up running…
Yeah. Seeing this stuff makes me nervous, because I worry that fastlane is doing a bunch of extra work that
- at best, I don’t care about or
- at worst, is going to cause problems that I have to fix (don’t laugh, read on…)
I now know that fastlane is buggy, especially in the realm of generating test reports. There are two main ways to do this with fastlane and both of them are bad.
xcpretty, the default. This tries to generate test results by parsing Xcode’s output while it runs tests. If you’ve ever written a tool that tries to parse another piece of software’s logs, you know how insane and fragile this is. Unsurprisingly, this results in errors like success/fail being mixed up or large numbers of tests being missed entirely.
trainer, a fastlane plugin. This does the sane thing of actually reading the Xcode test report. But while working on it I found two bugs that made it unsuitable for use on Jenkins (it doesn’t handle Jenkins workspaces well, and you end up with weird test durations and test suites when Jenkins parses the report).
All software has bugs, I don’t blame fastlane for this. But what makes it awful is that
Everyone uses fastlane
Have you ever needed to go to a government office to get some bureacratic paperwork processed? Or have you ever needed to go to your cable company’s office in person to exchange some hardware or resolve a billing dispute?
These are universally awful experiences and I theorize that they are both awful for these two reasons:
- They have to serve a wide audience with a broad range of needs and capabilities
- The people being served are only there out of necessity and would much rather be doing something else
These translate into awfulness because the employees need to treat every customer like they have the same lowest possible baseline of intelligence. It doesn’t matter if you’re a professional network engineer, the cable company is going to make sure you restart your computer and check the internet again before they replace your cable modem that is literally on fire. And the employees aren’t entirely at fault because the people are desperate to get out of there, meaning they are liable to misrepresent facts, misreport problems, and often expect the employees to magically fix things that are completely out of their control.
fastlane’s bug tracker is exactly this situation.
Because it’s advertised as a time-saving miracle tool, lots of people use it. Because it tries to do all things iOS, people use it for a broad set of unrelated tasks. And people only show up in the bug tracker because all of a sudden they’re losing money and the only thing they know is that they’re running a fastlane command and getting an error message.
So getting a fastlane bug addressed is like waiting in line in the customer service department of your nightmares. If they listen to you at all it’s going to take a long time, and even longer for them to actually fix anything.
Because I never witnessed a bug report being addressed by fastlane developers, I ended up doing a lot of build debugging myself. Here’s the problem: Xcode is a really complicated tool and fastlane is a really complicated tool and fastlane needs to run Xcode to do almost anything. Surprisingly, it’s way harder to debug fastlane than it is to debug Xcode! It took me longer than I’d like to admit to realize this.
Once I finally stopped relying entirely on fastlane and started running Xcode commands directly, it became much easier to realize which problems were coming from where.
But while the Xcode problems were easy to debug because I could ignore the complexity of fastlane, I still would have to figure out how to make my solution work in fastlane. Like restarting tests if they fail for a very particular, mysterious reason; it wasn’t obvious how to do that in fastlane even though I knew exactly where that error appeared and in what Xcode command. And the fastlane problems were essentially unfixable as discussed in the previous section.
Again, I kept coming to the question, “Why am I even using this tool?”
Unrelated, but it seems like fastlane is kind of obsessed with them. I don’t get it. It’s weird right?
So we ditched fastlane. What now? I replaced it with four scripts. If you read my Jenkins post, the three bash scripts directly match the three steps in our Jenkins pipeline.
The simplest, sets up dependencies since Jenkins always starts with a clean
workspace. The only gem we need is
xcpretty, which has only one other
Pretty self-explanatory. I only use that
DERIVED_DATA variable so that it’s
easy to comment out in case I want to run with the default path. And note that I
xcpretty. It sucks at test reports, but it does make the log easier
And lastly, look at that simple fix for random cycle errors. We first try an incremental build (if the workspace wasn’t clean). If we see that error, clean it and start again. If it still fails, the cycle is probably legitimate.
Slightly more complicated. Sometimes Xcode really doesn’t want to start those tests, so this loops 5 times, only exiting the loop if the results did not show that random failure to start.
I was very hesitant to make this script for generating test reports. Perhaps the “proper” way to do this would be to use extensible stylesheet language transformations (XSLT) to transform Xcode’s test report plist (which is XML) into the JUnit report (which is slightly reorganized XML). But, first of all, I didn’t even know XSLT was a thing before finding this blog post about it when researching this exact issue. Secondly, XSLT seems to be some ancient lost art that would involve buying and reading a book from the 90s before I can even start hacking on it (seriously, bravo to XML; you have further secured your position as the most over-engineered language). Third, I love me some Ruby.
So I won’t paste this here because it’s a bit more beefy, though still less than 100 lines of Ruby. It’s on my github. Check the readme for the benefits of using it.
First, most importantly, our continuous integration reliability has shot through the roof. Previously I felt like I had to babysit it every day, constantly diagnosing whether build or test failures were legitimate. Consequently the rest of my team never trusted it.
Hopefully, from now on, errors should be actual errors that developers need to address in their code.
Secondly, I feel much more in control of our build process. Yes, less code is better code, and I did have to write more code to get rid of fastlane. But that increase in code size is utterly dwarfed by the 67 dependencies we were able to eliminate, even ignoring the increased reliability of the process. If something goes wrong, there are very few places I have to look.
This build process is easy to test, since you can just run the separate scripts yourself, or even copy-paste their commands directly into your terminal. I don’t need fastlane’s entire environment present to support the simple build commands I need.
fastlane doesn’t suck
But fastlane isn’t useless! I’m only critical of it in the realm of continuous integration where, as I explained, I think its meager benefits do not outweigh its costs.
But it has tons of other functionality, for example automated screenshots and automated deployments, that I wouldn’t dare replace with hacked-together shell scripts. We still have a Fastfile sitting around in our repo, we just don’t use it as often anymore.