Coroutine scheduler monitoring

Are there any monitoring tools available for how many coroutines are currently active and their state etc? It would be nice if it could be exposed so that something like Prometheus can scrape it and visualise it in grafana.

It will also help in debugging leaks - and errors that might occur if we see coroutines just rising linearly

If not can this be done by looking at the thread stats instead?

Go exposes it via runtime.NumGoroutines()

Related:? https://github.com/Kotlin/kotlinx.coroutines/issues/494

[glasser]

Interesting — is there a branch or design doc or something for the reworking? Curious how it’s changing.

My proposal is pretty simple. A few of the core objects involved with coroutine scheduling should be (a) publicly accessible and (b) expose a few properties that provide statistics about them. It’s fine if these are documented as “experiment, up for change, don’t rely on this” and as “fetching these properties may have a performance impact if done frequently” (eg, ConcurrentLinkedQueue.size is O(n)).

Most specifically, I’d want to have access to

• ExperimentalCoroutineDispatcher.coroutineScheduler (which perhaps would return an interface declared to only contain the metrics below)
• LimitingDispatcher.queueSize: Int
• CoroutineScheduler.corePoolSize: Int
• CoroutineScheduler.maxPoolSize: Int
• CoroutineScheduler.queueSizes: Map<WorkerState, List<Int>>
• CoroutineScheduler.globalQueueSize: Int
• CoroutineScheduler.schedulerName: String (for tagging in the unlikely case of multiple schedulers) (ie, basically all the stuff in CoroutineScheduler.toString(); I think getting the control state isn’t super necessary.)

I don’t need kotlinx.coroutines to provide any machinery for hooking this up to my metrics service: I’m happy to keep at application (or external library) level the code that takes the dispatchers I care about, polls them for metrics, and publishes to my metrics service of choice.

[qwwdfsad]

We aim to implement it in the next releases after 1.5.0