Fix dropping database under write load #4580
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If a drop database is executed while writes are in flight, a panic could occur because the WAL would fail to write to the DB dirs where had been removed. Partil fix for #4538
If an error occurred in this code path, the locks would not be released.
If a database is dropped, the WAL maintenance goroutines could still kick in an fail becase the DB dirs are gone.
The shards map still held a reference to a shard that was dropped which caused the periodic mainteance task to report errors continuously.
Prevents a race where shards are recreated after a database is dropped.
When a database is dropped, removing old segments returns an error because the files are already gone. Using RemoveAll handles this case more gracefully.
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jwilder
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Oct 26, 2015
Fix dropping database under write load
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Fixes a number of issues that occur when dropping a database under write load.
Initially, the changes were to prevent panics that occurred with trying to create a new WAL segment in a DB dir that had been removed. When those were fixed, a full DB deadlock occurred due to WAL locks not being released when errors were returned. When those were fixed, shards were getting re-created on writes because we deleted the DB state before updating the meta-store which cause the
PointsWriterto fall into the case where it should create a shard that does not exist locally. This also uncovered that shard references were not fully removed from thetsdb.Storewhen a database was dropped which cause spurious errors in the logs due to the long-running periodic maintenance task goroutines. Finally, the WAL was not closed when a shard was closed which also led to spurious errors in the logs.Fixes #4538