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https://issues.apache.org/jira/browse/HBASE-8747?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andrew Purtell updated HBASE-8747:
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Affects Version/s: 0.94.9
This is great. I volunteer to port back into 0.94. Please let me know how/if I
can help in addition.
> Log when blocked longer than expected on a lock/synchronized block
> ------------------------------------------------------------------
>
> Key: HBASE-8747
> URL: https://issues.apache.org/jira/browse/HBASE-8747
> Project: HBase
> Issue Type: Improvement
> Components: Usability
> Affects Versions: 0.95.2, 0.94.9
> Reporter: stack
> Assignee: stack
> Priority: Critical
>
> Recently, on an internal support thread, the support folks asked that HBase
> surface when it is blocked up internally or an internal resource is highly
> contended. I replied in essence that this would be 'too hard'. Our Todd
> instead suggested:
> {quote}
> ...straw man proposal:
> - swap out all our use of sychronized (...) for ReentrantLock (probably most
> of our locking is already based on j.u.c locks anyway for rwlock purposes)
> - build a wrapper around ReentrantLock that looks something like:
> class AwesomeLock implements Lock {
> AwesomeLock(Lock realLock, int expectedAcquisitionTime, String metricName) {
> this.realLock = realLock;
> }
> public void lock() {
> if (realLock.tryLock(expectedAcquisitionTime, MILLIS)) { return; }
> Stopwatch sw = new Stopwatch();
> // collect realLock.getOwner()
> realLock.lock();
> long elapsed = sw.elapsed() + expectedAcquisitionTime;
> if (elapsed > expected * 2) { LOG.warn("Waited too long for lock which
> was held by owner " + owner); }
> collect metrics about how long the lock took, the lock name etc
> }
> }
> Basically the idea is that any possible point of contention should emit log
> messages and metrics when contended.
> {quote}
> Let me do the above over the next week or so.
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