influxdata / influxdb

Scalable datastore for metrics, events, and real-time analytics
https://influxdata.com
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fix: prevent retention service from hanging #25077

Closed gwossum closed 3 months ago

gwossum commented 3 months ago

Fix issue that can cause the retention service to hang waiting on a Shard.Close call. When this occurs, no other shards will be deleted by the retention service. This is usually noticed as an increase in disk usage because old shards are not cleaned up.

The fix adds to new methods to Store, SetShardNewReadersBlocked and InUse. InUse can be used to poll if a shard has active readers, which the retention service uses to skip over in-use shards to prevent the service from hanging. SetShardNewReadersBlocked determines if new read access may be granted to a shard. This is required to prevent race conditions around the use of InUse and the deletion of shards.

If the retention service skips over a shard because it is in-use, the shard will be checked again the next time the retention service is run. It can be deleted on subsequent checks if it is no longer in-use. If the shards is stuck in-use, the retention service will not be able to delete the shards, which can be observed in the logs for manual intervention. Other shards can still be deleted by the retention service even if a shard is stuck with readers.

This is a port of ad68ec8 from master-1.x to main-2.x.

closes: #25076 (cherry picked from commit b4bd607eefe4af3c38a73a5883866a66daecd7db)