RedisConnection#Connect(): get rid of spin lock #10265
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Al2Klimov
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area/icingadb
yhabteab
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Jan 13, 2025
lib/icingadb/redisconnection.cpp
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| @@ -340,7 +334,7 @@ void RedisConnection::Connect(asio::yield_context& yc) | |||
| } | |||
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| Handshake(conn, yc); | |||
| waitForReadLoop(); | |||
| m_NoQueuedReads.Wait(yc); | |||
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I often struggle to differentiate between the AsioConditionVariable::Clear() and AsioConditionVariable::Set() methods since they seem to perform very similar functions, and neither of them includes a clear comment explaining their purpose. And yet, I had to trace on my own to understand why the init parameter is set for this in the constructor but not for the others. Could you please provide some comments explaining the scenarios in which this gets unblocked? Additionally, I would suggest naming that new property something like m_ReadLoopDone to better reflect its original intentions.
The current implementation is rather similar to Python's threading.Event, than to a CV.
Instead of IoEngine::YieldCurrentCoroutine(yc) until m_Queues.FutureResponseActions.empty(), async-wait a CV which is updated along with m_Queues.FutureResponseActions.
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Al2Klimov
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Jan 29, 2025
| @@ -145,14 +145,14 @@ class TerminateIoThread : public std::exception | |||
| }; | |||
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| /** | |||
| * Condition variable which doesn't block I/O threads | |||
| * Awaitable flag which doesn't block I/O threads, inspired by threading.Event from Python | |||
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Please see the updated docs of the class in question.
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Instead of IoEngine::YieldCurrentCoroutine(yc) until m_Queues.FutureResponseActions.empty(), async-wait a CV which is updated along with m_Queues.FutureResponseActions.
👍 Re-connect still works on Redis restart, even if latter interrupted an outgoing message!
ref/NC/820479
claimed they start Icinga 2 with Icinga DB enabled – and it OOMs. I hope this spin lock is not responsible, but better safe than sorry.
Also, I'm sure we all agree that spin locks should be avoided, at least where easily possible.