RE: [VOTE] Maven incremental build for BIG-sized projects with local and remote caching
This feature caches Tests results too, but granularity is per-project. In our case we even cache result of long-running integration tests as well so developers rerun unit/integration tests only for changed projects and dependents from them. That’s significant time win.
In our multi module project if you change just 1 module of 600, you invalidate only that module and run test for that module.
If project is invalidated by changed inputs – it will be rebuild from scratch by usual plugins regardless of which features are supported by particular plugin. In case of Takari and incremental compiler that will result in faster compilation for second and consequent runs.
Any plugin could benefit from cache/incremental nature for multi-module project.
From: Tibor Digana [mailto:[hidden email]]
Sent: Friday, September 13, 2019 5:18 PM
To: Maven Developers List <[hidden email]>
Cc: Alexander Ashitkin <[hidden email]>
Subject: Re: [VOTE] Maven incremental build for BIG-sized projects with local and remote caching
In theory, the incremental compiler would make it faster.
But this can be told only if you present a demo project with has trivial tests taking much less time to complete than the compiler.
In reality the tests in huge projects take significantly longer time than the compiler.
Some developers say "switch off all the tests" in the release phase but that's wrong because then the quality goes down and methodologies are broken.
I can see a big problem that we do not have an interface between Surefire and Compiler plugin negotiating which tests have been modified including modules and classes in the entire structure.
Having incremental compiler is easy, just use compiler:3.8.1 or use the Takari compiler.
But IMO the biggest benefit in performance would be after having the truly incremental test executor.
We want to create upstream change to Maven to support true incremental build for big-sized projects.
To raise a pull request we have to pass long chain of Deutsche Bank’s internal procedures. So, before starting the process we would like to get your feedback regarding this feature.
Our project is hosted in mono-repo and contains ~600 modules. All modules has the same SNAPSHOT version.
There are lot of test automation around this, everything is tested before merge into release branch.
Current setup helps us to simplify build/release/dependency management for 10+ teams those contribute into codebase. We can release everything in 1-click.
The major drawback of such approach is build time: full local build took 45-60 min (-T8), CI build ~25min(-T16).
To speed-up our build we needed 2 features: incremental build and shared cache.
Initially we started to think about migration to Gradle or Bazel. As migration costs for the mentioned tools were too high, we decided to add similar functionality into Maven.
Current results we get: 1-2 mins for local build(-T8) if build was cached by CI, CI build ~5 mins (-T16).
The idea is to calculate checksum for inputs and save outputs in cache.
Each node checksum calculated with:
• Effective POM hash
• Sources hash
• Dependencies hash (dependencies within multi-module project)
Project sources inputs are searched inside project + all paths from plugins configuration:
How does it work in practice:
1. CI: runs builds and stores outputs in shared cache
2. CI: reuse outputs for same inputs, so time is decreasing
3. Locally: when I checkout branch and run ‘install’ for whole project, I get all actual snapshots from remote cache for this branch
4. Locally: if I change multiple modules in tree, only changed subtree is rebuilt
Impact on current Maven codebase is very localized (MojoExecutor, where we injected cache controller).
Caching can be activated/deactivated by property, so current maven flow will work as is.
And the big plus is that you don’t need to re-work your current project. Caching should work out of box, just need to add config in .mvn folder.
Please let us know what do you think. We are ready to invest in this feature and address any further feedback.
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