Append-entries support partial success return value #822
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Thanks. Following my comment in the timeout PR, the timeout already on the first entry would be then represented as |
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drmingdrmer
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If there are too many log entries and the `RPCOption.ttl` is not sufficient, an application can opt to only send a portion of the entries, with `AppendEntriesResponse::PartialSuccess(Option<LogId>)`, to inform Openraft with the last replicated log id. Thus replication can still make progress. For example, it tries to send log entries `[1-2..3-10]`, the application is allowed to send just `[1-2..1-3]` and return `PartialSuccess(1-3)`, ### Caution The returned matching log id must be **greater than or equal to** the first log id(`AppendEntriesRequest::prev_log_id`) of the entries to send. If no RPC reply is received, `RaftNetwork::send_append_entries` **must** return an `RPCError` to inform Openraft that the first log id(`AppendEntriesRequest::prev_log_id`) may not match on the remote target node. - Fix: databendlabs#822
Ack, thanks. |
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Ack, thanks. |
drmingdrmer
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If there are too many log entries and the `RPCOption.ttl` is not sufficient, an application can opt to only send a portion of the entries, with `AppendEntriesResponse::PartialSuccess(Option<LogId>)`, to inform Openraft with the last replicated log id. Thus replication can still make progress. For example, it tries to send log entries `[1-2..3-10]`, the application is allowed to send just `[1-2..1-3]` and return `PartialSuccess(1-3)`, ### Caution The returned matching log id must be **greater than or equal to** the first log id(`AppendEntriesRequest::prev_log_id`) of the entries to send. If no RPC reply is received, `RaftNetwork::send_append_entries` **must** return an `RPCError` to inform Openraft that the first log id(`AppendEntriesRequest::prev_log_id`) may not match on the remote target node. - Fix: databendlabs#822
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An application can use this feature to send part of the log entries and return to the caller only the ones that were successfully replicated to a remote node.
Why
If there are too many log entries and the
RPCOption.ttlis not sufficient, an application can opt to only send a portion of the entries. Thus replication can still make progress.Changes
For better compatibility, simply add a new variant to the return value type of the append-entries RPC. Applications that do not need partial success can continue to function as is. However, for those applications that do use this feature, they can return
PartialSuccessinstead ofSuccessto provide Openraft with information on which log entries have been successfully replicated.Here are the changes that are being suggested:
pub enum AppendEntriesResponse<NID: NodeId> { Success, + PartialSuccess(Option<LogId<NID>>), Conflict, HigherVote(Vote<NID>), }Requirement is discussed in:
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