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eBay / NuRaft

C++ implementation of Raft core logic as a replication library
Apache License 2.0
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This is a question, not an issue. About `state_machine::pre_commit` #474

Closed zidian666 closed 10 months ago

zidian666 commented 10 months ago

https://github.com/eBay/NuRaft/blob/e66b4b65c90ff3a0be852d484bf15583672ea7fd/include/libnuraft/state_machine.hxx#L99

I'm confused about the return value of this function.

If I want to return a non-null pointer, how can I know NuRaft how to deserialize it ?

Actually, I'm going to let state_machine::pre_commit return a failure to make pre-commit fail. Or is there another way to make pre-commit fail ?

Thanks.

greensky00 commented 10 months ago

@zidian666 pre_commit is executed right after appending the log to log store, hence it is not possible to make it fail; once a log is appended, it should be replicated. commit may not be invoked according to the consensus result though.

The return value of pre_commit is not used in normal path. There is a special option asynchronous replication which returns the result of pre_commit without waiting for the consensus. Other than that, its return value is just ignored.