Fix performance issues when caching maven repository

There are huge performance issues with the caching mechanism of maven repositories

In the middle of the day, when building a maven artefact, to fetch the cache when my actions run can take from 2-3 minutes (!)

Then my maven build is done in 20-30 seconds…

After my build, then It takes approx one and a half minute before the cache is saved…

When the performance of the caching of the repository is so bad, it is better to run without caching (!). This is a serious setback in performance when developing and it is difficult to deliver code to our production environments in a quick manner.

I am sorry not to provide any examples, but my repositories are private belonging to https://github.com/navikt. A typical cache configuration looks like this:

      - uses: actions/cache@v1.1.2
        with:
          path: ~/.m2
          key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
          restore-keys: |
            ${{ runner.os }}-maven-

[dhadka]

Hi @jactor-rises, thanks for reporting this. Looking at our server-side telemetry for your repos, I’m not seeing any indication that calls to the cache server are slow. 95% of calls are completing in < 0.2 seconds. It’s likely either (1) slowness downloading the cache content from storage, or (2) slowness processing the cache action on the runner.

There are a couple of things you can try:

1. Enable debug logging and see if you can determine where the time is spent. You can also post a sample log here, or e-mail the log to dhadka (at) github (dot) com, and we can take a look.

2. There is a known issue where the hashFiles function can take a long time if it’s scanning a bunch of files. See https://github.com/actions/cache/issues/203, for example. Hopefully getting the debug logs will help determine if that’s the cause.

3. Check the size of the cache. If the cache is large, the time spent downloading and extracting the contents can add up. The debug logs should show the file size + the time to untar. If the issue is the time spent extracting the file, there is work underway to help improve that (https://github.com/actions/cache/issues/184).

4. Is the slowness you see occurring in all runs, or does it only occur periodically?

5. Make sure you’re using the latest version of the cache action. Using uses: actions/cache@v1 will always point to the latest version. I’m seeing a (very) small number of calls using an older (slower) version.

[jactor-rises]

…hmm… I have misread the documentation in that case… but it works for my purpose… it reduced the .m2-cached files from over 900 mb to amount 100 mb…