Sync up snapshot shard status on a master restart #11450
Merged
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When a snapshot operation on a particular shard finishes, the data node where this shard resides sends an update shard status request to the master node to indicate that the operation on the shard is done. When the master node receives the command it queues cluster state update task and acknowledges the receipt of the command to the data node.
The update snapshot shard status tasks have relatively low priority, so during cluster instability they tend to get stuck at the end of the queue. If the master node gets restarted before processing these tasks the information about the shards can be lost and the new master assumes that they are still in process while the data node thinks that these shards are already done.
This commit add a retry mechanism that checks compares cluster state of a newly elected master and the current state of snapshot shards and updates the cluster state on the master again if needed.
Closes #11314