Skip unavailable replicas in parallel distributed insert select

[tavplubix]

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• Improvement

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Skip unavailable replicas when executing parallel distributed INSERT SELECT

[robot-clickhouse]

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[tavplubix]

Not sure if we should add another setting (I don't like using skip_unavailable_shards for skipping unavailable replicas) or even do it by default
Also, it would be great to add a test

[tavplubix]

Not sure if we should add another setting (I don't like using skip_unavailable_shards for skipping unavailable replicas) or even do it by default

Although, look like we already use skip_unavailable_shards for skipping unavailable replicas in s3Cluster

[Avogar]

Although, look like we already use skip_unavailable_shards for skipping unavailable replicas in s3Cluster

Well, we explicitly set skip_unavailable_shards always to true in *Cluster functions:

ClickHouse/src/Storages/IStorageCluster.cpp

Lines 218 to 219 in 67f74b5

	/// Cluster table functions should always skip unavailable shards.
	new_settings.skip_unavailable_shards = true;

So, we if user changes skip_unavailable_shards it doesn't affect *Cluster functions. Also, I think we can change the code in IStorageCluster and don't copy settings with changed skip_unavailable_shards=true but just use optional skip_unavailable_endpoints argument of ConnectionPoolWithFailover::getMany.

But I guess we still use skip_unavailable_shards as skip unavailable replicas in clusterAllReplicas

[tavplubix]

But I guess we still use skip_unavailable_shards as skip unavailable replicas in clusterAllReplicas

It's fine because clusterAllReplicas means "treat each replica as a separate shard"

[tavplubix]

Integration tests (tsan) [3/6] - test_parallel_replicas_custom_key_failover was broken in master, reverted
Performance Comparison [1/4] - #59070
Stateful tests (tsan, ParallelReplicas) - 00165_jit_aggregate_functions is flaky (probably too long for tsan)
Stateless tests (release, analyzer) - 02901_parallel_replicas_rollup was broken in master, reverted
Stress test (msan) - #58509

[devcrafter]

If the comment at line 1152 is correct. Then PoolMode::GET_ONE is sufficient here

[tavplubix]

I guess the comment is either incorrect or misleading (because we get the cluster from StorageDistributed::getCluster()), we can ask @nikitamikhaylov

[tavplubix]

Yes, it's copy-paste from

ClickHouse/src/Storages/StorageReplicatedMergeTree.cpp

Lines 5562 to 5565 in 4315d44

	for (const auto & replicas : src_cluster->getShardsAddresses())
	{
	/// There will be only one replica, because we consider each replica as a shard
	for (const auto & node : replicas)

And looks like we have exactly the same issue in StorageReplicatedMergeTree::distributedWriteFromClusterStorage (and that's why we should avoid copy-paste when possible)