Handle ErrCompacted errors for Compact in raftexample

[chenyang8094]

When I adjust the value of defaultSnapshotCount to be smaller than snapshotCatchUpEntriesN in raftexample, because the compactIndex cannot be updated, a panic will occur when the snapshot is triggered for the second time, and the error is "panic: requested index is unavailable due to compaction".

This PR adds ErrCompacted error handling for Compact (keep consistent with etcd server).

[fuweid]

@chenyang8094 Thanks for the patch. For the DCO requirement, you need to git commit -s --amend --no-edit && git push

[jmhbnz]

Hey @chenyang8094 - Thanks for proposing this change.

Please be aware we are planning to remove contrib/raftexample from etcd.

There is an issue etcd-io/raft#2 to implement a self-contained raft example in the raft repo which has been worked on.

I'm not necessarily opposed to merging this, just making you aware of the other work underway. Will leave final merge decision to maintainers.

[chenyang8094]

@jmhbnz Thanks for the tip, I see it. IIUC, there seems to be a lot more to this work. raftexample is a great code for learning etcd/raft, let's improve it together.

[chenyang8094]

@jmhbnz Can you answer my doubts, thank you. #16425

[jmhbnz]

@jmhbnz Can you answer my doubts, thank you. #16425

Hey @chenyang8094 as mentioned above, I am not opposed to merging this, the code change looks ok to me, however it is now up to maintainers if they agree. @ahrtr WDYT?

[chenyang8094]

@jmhbnz I mean my Q&A, please click this link #16425

[chenyang8094]

@jmhbnz @ahrtr
Please help me take a look at this Static Analysis failure, what am I doing wrong?

[ahrtr]

Please gofmt the source file

[ahrtr]

Could you squash the commits?

[chenyang8094]

Could you squash the commits?

done

[ahrtr]

LGTM.

It matchs how etcd processes the compact.

etcd/server/etcdserver/server.go

Lines 2136 to 2138 in 6ef9c53

	if err == raft.ErrCompacted {
	return
	}