Intro - NUISTGY/MIT-6.824-Raft GitHub Wiki
Get code
$ git clone git://g.csail.mit.edu/6.5840-golabs-2023 6.5840
$ cd 6.5840
$ ls
Makefile src
$
$ cd ~/6.5840
$ git pull
...
$ cd src/raft
$ go test
Test (2A): initial election ...
--- FAIL: TestInitialElection2A (5.04s)
config.go:326: expected one leader, got none
Test (2A): election after network failure ...
--- FAIL: TestReElection2A (5.03s)
config.go:326: expected one leader, got none
...
$
The code
Implement Raft by adding code to raft/raft.go. In that file you'll find skeleton code, plus examples of how to send and receive RPCs. Your implementation must support the following interface, which the tester and (eventually) your key/value server will use. You'll find more details in comments in raft.go.
// create a new Raft server instance:
rf := Make(peers, me, persister, applyCh)
// start agreement on a new log entry:
rf.Start(command interface{}) (index, term, isleader)
// ask a Raft for its current term, and whether it thinks it is leader
rf.GetState() (term, isLeader)
// each time a new entry is committed to the log, each Raft peer
// should send an ApplyMsg to the service (or tester).
type ApplyMsg
A service calls Make(peers,me,…) to create a Raft peer. The peers argument is an array of network identifiers of the Raft peers (including this one), for use with RPC. The me argument is the index of this peer in the peers array. Start(command) asks Raft to start the processing to append the command to the replicated log. Start() should return immediately, without waiting for the log appends to complete. The service expects your implementation to send an ApplyMsg for each newly committed log entry to the applyCh channel argument to Make().
raft.go contains example code that sends an RPC (sendRequestVote()) and that handles an incoming RPC (RequestVote()). Your Raft peers should exchange RPCs using the labrpc Go package (source in src/labrpc). The tester can tell labrpc to delay RPCs, re-order them, and discard them to simulate various network failures. While you can temporarily modify labrpc, make sure your Raft works with the original labrpc, since that's what we'll use to test and grade your lab. Your Raft instances must interact only with RPC; for example, they are not allowed to communicate using shared Go variables or files.
Subsequent labs build on this lab, so it is important to give yourself enough time to write solid code.