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(Updated Sept. 14, 2016, 11:12 p.m.) Review request for Aurora, Joshua Cohen, Stephan Erb, and Zameer Manji. Changes ------- Rebasing and comments. Repository: aurora Description ------- This is the second part of the `BatchWorker` conversion work that moves cron jobs to use non-blocking kill followups and reduces the number of trigger threads. See https://reviews.apache.org/r/51759 for more background on the `BatchWorker`. #####Problem The current implementation of the cron scheduling relies on a large number of threads (`cron_scheduler_num_threads`=100) to support cron triggering and killing existing tasks according to `KILL_EXISTING` collision policy. This creates large spikes of activities at synchronized intervals as users tend to schedule their cron runs around similar schedules. Moreover, the current implementation re-acquires write locks multiple times to deliver on `KILL_EXISTING` policy. #####Remediation Trigger level batching is still done in a blocking way but multiple cron triggers may be bundled together to share the same write transaction. Any followups, however, are performed in a non-blocking way by relying on a `BatchWorker.executeWithReplay()` and the `BatchWorkCompleted` notification. In order to still ensure non-concurrent execution of a given job key trigger, a token (job key) is saved within the trigger itself. A concurrent trigger will bail if a kill followup is still in progress (token is set AND no entry in `killFollowups` set exists yet). #####Results The above approach allowed reducing the number of cron threads to 10 and likely can be reduced even further. See https://reviews.apache.org/r/51759 for the lock contention results. Diffs (updated) ----- commons/src/main/java/org/apache/aurora/common/util/BackoffHelper.java 8e73dd9ebc43e06f696bbdac4d658e4b225e7df7 commons/src/test/java/org/apache/aurora/common/util/BackoffHelperTest.java bc30990d57f444f7d64805ed85c363f1302736d0 config/findbugs/excludeFilter.xml fe3f4ca5db1484124af14421a3349950dfec8519 src/main/java/org/apache/aurora/scheduler/cron/quartz/AuroraCronJob.java c07551e94f9221b5b21c5dc9715e82caa290c2e8 src/main/java/org/apache/aurora/scheduler/cron/quartz/CronModule.java 155d702d68367b247dd066f773c662407f0e3b5b src/test/java/org/apache/aurora/scheduler/cron/quartz/AuroraCronJobTest.java 5c64ff2994e200b3453603ac5470e8e152cebc55 src/test/java/org/apache/aurora/scheduler/cron/quartz/CronIT.java 1c0a3fa84874d7bc185b78f13d2664cb4d8dd72f Diff: https://reviews.apache.org/r/51763/diff/ Testing ------- All types of testing including deploying to test and production clusters. Thanks, Maxim Khutornenko
