DatabaseReplicated: fix DDL query timeout after recovering a replica

[tavplubix]

Changelog category (leave one):

• Bug Fix (user-visible misbehavior in an official stable release)

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Some distributed DDL queries might show an error like Watching task ... is executing longer than distributed_ddl_task_timeout ... There are 1 unfinished hosts (0 of them are currently active), they are going to execute the query in background if some replica was recovering from a stale state when the query has started. It's fixed.

Fixes test_replicated_database/test.py::test_alters_from_different_replicas: https://pastila.nl/?0024df70/980a4c7882649f60e9174d3d46f85cc0#EB/kiQAvQYMP+9CfoC4LTg==

[robot-clickhouse]

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Check name	Description	Status
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Check name	Description	Status
Bugfix validate check	Checks that either a new test (functional or integration) or there some changed tests that fail with the binary built on master branch	❌ error
Integration tests	The integration tests report. In parenthesis the package type is given, and in square brackets are the optional part/total tests	❌ failure
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[tavplubix]

Bugfix validate check - OK, since this PR fixes the flaky test
Integration tests (asan) - test_ssl_cert_authentication was broken in master
Integration tests (asan, analyzer) [6/6] - #54502
Performance Comparison [3/4] - #56797

[bianpengyuan]

@tavplubix sorry for the dumb question, but if a new replica died between database being created and this line, next time when the replica is up, it will always be stuck on this line right? Since max_log_ptr_at_creation is always 0 (because this replica will now attach the database instead of creating it) and our_log_ptr is also 0. I seem to run into this situation when trying to make some code change, but I feel it is also possible to happen in reality?

[tavplubix]

It's a good question, you have found a bug! Yes, debug builds and builds with sanitizers will always crash on this line with SIGABRT. Release builds ignore assertions, so it will continue executing this code and will not create the nodes in zk. As a result, some DDL queries may throw Watching task {} is executing longer than distributed_ddl_task_timeout ... (if they started while the replica was being created)