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Fix a typo (#237)

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* Fix a typo

* Fix a typo
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Rapiz 2021-01-25 01:11:39 +08:00 committed by GitHub
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doc/project2-RaftKV.md
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@ -122,7 +122,7 @@ The format is as below and some helper functions are provided in `kv/raftstore/m
> You may wonder why TinyKV needs two badger instances. Actually, it can use only one badger to store both raft log and state machine data. Separating into two instances is just to be consistent with TiKV design.
These metadatas should be created and updated in `PeerStorage`. When creating PeerStorage, see `kv/raftstore/peer_storager.go`. It initializes RaftLocalState, RaftApplyState of this Peer, or gets the previous value from the underlying engine in the case of restart. Note that the value of both RAFT_INIT_LOG_TERM and RAFT_INIT_LOG_INDEX is 5 (as long as it's larger than 1) but not 0. The reason why not set it to 0 is to distinguish with the case that peer created passively after conf change. You may not quite understand it now, so just keep it in mind and the detail will be described in project3b when you are implementing conf change.
These metadatas should be created and updated in `PeerStorage`. When creating PeerStorage, see `kv/raftstore/peer_storage.go`. It initializes RaftLocalState, RaftApplyState of this Peer, or gets the previous value from the underlying engine in the case of restart. Note that the value of both RAFT_INIT_LOG_TERM and RAFT_INIT_LOG_INDEX is 5 (as long as it's larger than 1) but not 0. The reason why not set it to 0 is to distinguish with the case that peer created passively after conf change. You may not quite understand it now, so just keep it in mind and the detail will be described in project3b when you are implementing conf change.
The code you need to implement in this part is only one function: `PeerStorage.SaveReadyState`, what this function does is to save the data in `raft.Ready` to badger, including append log entries and save the Raft hard state.
@ -141,7 +141,7 @@ In project2 part A, you have built a tick-based Raft module. Now you need to wri
The Raft `RawNode` is already created with `PeerStorage` and stored in `peer`. In the raft worker, you can see that it takes the `peer` and wraps it by `peerMsgHandler`. The `peerMsgHandler` mainly has two functions: one is `HandleMsgs` and the other is `HandleRaftReady`.
`HandleMsgs` processes all the messages received from raftCh, including `MsgTypeTick` which calls `RawNode.Tick()` to drive the Raft, `MsgTypeRaftCmd` which wraps the request from clients and `MsyTypeRaftMessage` which is the message transported between Raft peers. All the message types are defined in `kv/raftstore/message/msg.go`. You can check it for detail and some of them will be used in the following parts.
`HandleMsgs` processes all the messages received from raftCh, including `MsgTypeTick` which calls `RawNode.Tick()` to drive the Raft, `MsgTypeRaftCmd` which wraps the request from clients and `MsgTypeRaftMessage` which is the message transported between Raft peers. All the message types are defined in `kv/raftstore/message/msg.go`. You can check it for detail and some of them will be used in the following parts.
After the message is processed, the Raft node should have some state updates. So `HandleRaftReady` should get the ready from Raft module and do corresponding actions like persisting log entries, applying committed entries
and sending raft messages to other peers through the network.