TEZ-4580: Slow preemption of new containers when re-use is enabled #374
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himanshu-mishra
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Sep 27, 2024
| if (delayedContainers.remove(container)) { | ||
| LOG.info("Removed {} from delayed containers", container.getContainer().getId()); | ||
| } else { | ||
| LOG.warn("Unknown container {} sent for removal. Ignoring.", container.getContainer().getId()); |
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A valid case here is when a new container is allocated - added to delayedContainers, it is polled (removed) from queue but if there is no pending task request releaseContainer() is invoked. Please suggest if the log level should be changed in info or for both the newly added logs should be at debug.
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prabhjyotsingh
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…nmerged) apache#374 (cherry picked from commit aea86ca)
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…enabled (unmerged) apache#374 (#24) (cherry picked from commit aea86ca)
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…enabled (unmerged) apache#374 (#24) (cherry picked from commit aea86ca)
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When container reuse is enabled, preemption of lower priority containers that are not yet assigned to task, takes long time as they are released one at a time, and not the number of containers based when tez.am.preemption.percentage is high added in https://issues.apache.org/jira/browse/TEZ-1742.
Further investigation lead to following conclusion:
Warn log / Assertion error thrown because in preemptIfNeeded(), when releasing new containers, the loop counter is being decremented with each
releaseUnassignedContainers, leading to looping only half number of times. By using another counter, assertion passes because of condition method returns with checkif (numPendingRequestsToService < 1) {.In releaseContainer(), the container is not getting removed from
delayedContainersqueue and only fromheldContainersmap, hence same container is being picked up for release in every iteration till next cycle ofDelayedContainerManagerfinds out that the container is not inheldContainersand skips it with logSkipping delayed container as container is no longer running, containerId=...This change adds a method in
DelayedContainerManagerto allow removal of delayed container and invokes it in releaseContainer method, which so far only removed it fromheldContainersmap.