Remove expiringmap in favour of caffeine

[SimunKaracic]

The expiringMap dependency has been replaced with caffeine https://github.com/ben-manes/caffeine.

This should fix #110.

I have a small reproduction example, based on https://github.com/akka/akka-samples/tree/2.6/akka-sample-distributed-workers-scala/src/main/scala/worker, and I've been unable to get this PR to deadlock in 2k startups of the app.

All tests pass, most Kamon tests pass (expect for kamon-annotation, which depend on expiringMap being inside the kanela jar, but I have that fixed locally and can open another PR if this goes through).

The only downside I see is that the agent jar file has grown in size from 5.4 MB to 6.4 MB.

Check it out and let me know what you think

[dpsoft]

Hi @SimunKaracic thanks for proposing this PR, I thinking that using this: https://github.com/raphw/weak-lock-free/blob/master/src/main/java/com/blogspot/mydailyjava/weaklockfree/WeakConcurrentMap.java + a ScheduledThreadPoolExecutor is enough WDYT?

[pseudocode]

import com.blogspot.mydailyjava.weaklockfree.WeakConcurrentMap

private final WeakConcurrentMap<Object, TypePool.CacheProvider> cache =
        new WeakConcurrentMap<Object, TypePool.CacheProvider>(false);

Executors.newScheduledThreadPoolExecutor("cache-pool-cleaner") //deamon
            .scheduleWithFixedDelay(new Runnable() {
                @Override
                public void run() {
                    cache.expungeStaleEntries();
                }
            }, 1, 1, TimeUnit.MINUTES);

[SimunKaracic]

Sure I can try to put that in and run all the tests, should be simple enough.

The reason I used caffeine was because I wanted a popular, safe solution.
But I also wasn't sure of what exactly were the usage parameters for the ExpiringMap.

I'll put this in, rerun all the tests, and report back!

But on the final decision on this, I'll defer to your expertise

[SimunKaracic]

Pushed the new version in, the deadlock tests are still running, but kamon tests pass.

A couple differences:

1. Kamon-annotation will need an actual cache implementation (caffeine? :D), or some bigger code changes.
2. There's no way to specify a loader, so I added a simple null check to the locate method that fills the map with data.
3. The jar size did not go down :/

[dpsoft]

Awesome! I think in relation to the point 1 we have 2 options:

1 - Keep using ExpiringMap or
2 - Caffeine in favor to Expiring map

in both options we need shade the dependency in this manner:

https://github.com/kamon-io/Kamon/blob/master/build.sbt#L339-L342

[dpsoft]

@SimunKaracic done!

[SimunKaracic]

🎉
Thanks for the assist!

I'll go on kamon next, I'll keep the expiringmap and just add it as a shaded dependency!

[ivantopo]

Please, don't keep expiring map! We already know it has a concurrency bug in there. We should not spread the chances of that bug biting us again.

[SimunKaracic]

Good point!
WIll replace it with caffeine