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I’m actually learning MIT6.824,
and try to implement its lab,
there’s a paragraph in raft’s paper describing client semantics:
Our goal for Raft is to implement linearizable seman- tics (each operation appears to execute instantaneously, exactly once, at some point between its invocation and its response). However, as described so far Raft can exe- cute a command multiple times: for example, if the leader crashes after committing the log entry but before respond- ing to the client, the client will retry the command with a new leader, causing it to be executed a second time. The solution is for clients to assign unique serial numbers to every command. Then, the state machine tracks the latest serial number processed for each client, along with the as- sociated response. If it receives a command whose serial number has already been executed, it responds immedi- ately without re-executing the
Now I have passed MIT lab 3A, but I have responses map[string]string in kvserver,
which is a map from client’s request id to response, but the problem is then the
map will keep increasing if client’s keep sending request, Which is problemic in real project. How does Raft handle this in real project? Also, the MIT lab 3 says one client
will execute one command at a time, so probably I can optimize by deleting client’s last request’s response. But how does Raft handle this in real project where client’s behavior is more free?
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