Make snapshot deletion faster #2
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The delete snapshot task takes longer than expected. A major reason for this is that the (often many) stale indices are deleted iteratively. In this commit we change the deletion to be concurrent using the SNAPSHOT threadpool. Notice that in order to avoid putting too many delete tasks on the threadpool queue a similar methodology was used as in `executeOneFileSnapshot()`. This is due to the fact that the threadpool should allow other tasks to use this threadpool without too much of a delay. fixes issue elastic#61513 from Elasticsearch project
nknize
reviewed
Feb 26, 2021
| "[{}] index {} is no longer part of any snapshots in the repository, " + | ||
| "but failed to clean up their index folders", metadata.name(), indexSnId), e); | ||
| } | ||
| final int workers = Math.min(threadPool.info(ThreadPool.Names.SNAPSHOT).getMax(), staleIndicesToDelete.size()); |
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Is it possible for staleIndicesToDelete to exceed the max threadPool size?
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Yes, this is very much possible as the max threads in this threadpool is 5 and number of stale indices can be easily in the dozens if not more. This is defined in the ThreadPool class constructor, the max is: org.elasticsearch.threadpool.ThreadPool#halfAllocatedProcessorsMaxFive.
The reason we take the min of the two is in case there are indeed less than 5 deletions required.
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The delete snapshot task takes longer than expected. A major reason for this is
that the (often many) stale indices are deleted iteratively.
In this commit we change the deletion to be concurrent using the SNAPSHOT threadpool.
Notice that in order to avoid putting too many delete tasks on the threadpool
queue a similar methodology was used as in
executeOneFileSnapshot(). This is due tothe fact that the threadpool should allow other tasks to use this threadpool without
too much of a delay.
fixes issue elastic#61513 from Elasticsearch project