KeyDB – multi-threaded Redis fork by Snapchat

Re:KeyDB – multi-threaded Redis fork by Snapchat by byby on Sunday May 21, 2023 @11:14AM (#36021803)

Side question about redis:

Does redis do async operations? I'm not sure how that would work because it's known to be in memory. But I do know it persists to disk. So basically my question is:

Does almost absolutely every operation on a redis database happen serially? Maybe not every single operation, but in general.

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Re:KeyDB – multi-threaded Redis fork by Snapchat by T0pH4t on Sunday May 21, 2023 @11:35AM (#36021997)

Sort of. To my knowledge, the original redis was literally signal threaded and performed io on the same threads as managing the DB (asynchronously of coarse). Then after either redis 5 or 6 they added IO threads to redis such that the DB stayed managed by a single thread and network/disk IO happened on the IO threads.

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Re:KeyDB – multi-threaded Redis fork by Snapchat by byby on Sunday May 21, 2023 @01:10PM (#36022885)

It makes sense for disk persistence to be io but redis is primarily in memory. So I don't think async applies to that aspect of it. In theory that makes it so all operations on the database from the user perspective are serial.

Not sure about this that's why I'm asking here for a definitive concrete answer about this.

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Re:KeyDB – multi-threaded Redis fork by Snapchat by drwiggly on Sunday May 21, 2023 @11:34AM (#36021986)

Every user/client operation is serial.

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Re:KeyDB – multi-threaded Redis fork by Snapchat by byby on Sunday May 21, 2023 @01:09PM (#36022867)

This is mainly because it's single threaded and operates on in memory state. Async io doesn't apply to in memory so all operations have to be serial, is this characterization correct? Thanks.

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