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WIP: Analysis: LockedSemiSyncMaster #1173
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A new analysis entry aimed to identify a blocked semi-sync master situation.
Example scenario depicted in #1137
e.g. a master has a single semi-sync replica and a configuration of:
rpl_semi_sync_master_enabled=ONrpl_semi_sync_master_timeout=10000000000rpl_semi_sync_master_wait_for_slave_count=1if the semi-sync replica goes down, the master blocks writes. We want to identify this as a failure scenario (a recovery might be: enable semi-sync on a different replica).
However, we probably also want to make this detection only after some X seconds, because due to the nature of the setup, it may be normal for the master to block for 1 or 2 seconds occasionally.
The issue right now (which is why this PR is WIP at this time) is to be able to reliably say "the master has been blocked since 20sec ago". There's various ways to go about that, which I'm exploring.