On 1/7/21 12:57 PM, Jason Mehrens wrote:
Hi Doug,
What are your thoughts on promoting monitoring methods from TPE and or FJP to
AbstractExecutorService? The default implementations could just return -1. An
example precedent is OperatingSystemMXBean::getSystemLoadAverage. The
Executors.DelegatedExecutorService could then be modified to extend
AbstractExecutorService and forward the new methods and the existing
AES::taskFor calls when the wrapped Executor is also an
AbstractExecutorService. The return types of the Executors.newXXX would remain
the same.
Maybe. But for now, here's a cheap trick that might be tolerable: Add to
DelegatedExecutorService:
public String toString() { return e.toString(); }
The juc executors (ThreadPoolExecutor and ForkJoinPool that could be
wrapped here) both print pool size, active threads, queued tasks, and
completed tasks. It would require not-very-pleasant string parsing in
monitoring tools, but this might be good enough for Micrometer and others?
I suppose the tradeoff is that adding any new default method to ExecutorService
and or new methods to AbstractExecutorService could break 3rd party code.
Jason
________________________________________
From: core-libs-dev <core-libs-dev-r...@openjdk.java.net> on behalf of Doug Lea
<d...@cs.oswego.edu>
Sent: Thursday, January 7, 2021 7:09 AM
To: core-libs-dev@openjdk.java.net
Subject: Re: Monitoring wrapped ThreadPoolExecutor returned from Executors
On 1/5/21 10:11 PM, Tommy Ludwig wrote:
In the Micrometer project, we provide metrics instrumentation of
`ExectorService`s. For `ThreadPoolExecutor`s, we track the number of completed
tasks, active tasks, thread pool sizes, task queue size and remaining capacity
via methods from `ThreadPoolExecutor`. We are currently using a brittle
reflection hack[1] to do this for the wrapped `ThreadPoolExecutor` returned
from `Executors` methods `newSingleThreadExecutor` and
`newSingleThreadScheduledExecutor`. With the introduction of JEP-396 in JDK 16,
our reflection hack throws an InaccessibleObjectException by default.
I am not seeing a proper way to get at the methods we use for the metrics (e.g.
`ThreadPoolExecutor::getCompletedTaskCount`) in this case. Is there a way that
I am missing?
There's no guarantee that newSingleThreadExecutor returns a restricted
view of a ThreadPoolExecutor, so there can't be a guaranteed way of
accessing it,
But I'm sympathetic to the idea that under the current implementation
(which is unlikely to change anytime soon), the stats are available, and
should be available to monitoring tools. But none of the ways to do this
are very attractive: Creating a MonitorableExecutorService interface and
returning that? Making the internal view class public with a protected
getExecutor method?
