fix: skip heartbeat if shard is under global lock #4882
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Signed-off-by: kostas <[email protected]>
kostasrim
commented
Apr 3, 2025
| if (db_slice.WillBlockOnJournalWrite()) { | ||
| // We acquire exlusive locks during global transactions | ||
| // If we can't acquire this it means the shard is under global lock. | ||
| const bool can_acquire_global_lock = shard_lock()->Check(IntentLock::Mode::EXCLUSIVE); |
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note, we don't acquire here, namely we don't increment Cx and Cs (exlusive and shared intent locks). We merely test them to understand if we are under global lock or not.
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I will follow with another PR, to fix preemption during heartbeat. This is the last corner case. |
adiholden
reviewed
Apr 3, 2025
src/server/engine_shard.cc
Outdated
| @@ -735,11 +735,14 @@ void EngineShard::Heartbeat() { | |||
| DbSlice& db_slice = namespaces->GetDefaultNamespace().GetDbSlice(shard_id()); | |||
| // Skip heartbeat if we are serializing a big value | |||
| static auto start = std::chrono::system_clock::now(); | |||
| if (db_slice.WillBlockOnJournalWrite()) { | |||
| // We acquire exlusive locks during global transactions | |||
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Lets update the comment,
How about: Skip heartbeat if global transaction is in process. This is determined by attempting to check if shard lock can be acquired.
adiholden
approved these changes
Apr 7, 2025
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We allowed running
heartbeatduringglobal transactions. That's not good. For example, during replication and while transitioning from full to stable sync we unregister and register journal callbacks with a preemption inbetween. If under preemption heartbeat runs, then we loose those journal entries triggering an lsn check failure.Fixes another corner case in #4048