Support checking assertion of Leadership #625
Open
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
This is a follow up to #560 |
otoolep
commented
Oct 16, 2024
| @@ -788,6 +802,7 @@ func (r *Raft) leaderLoop() { | |||
| oldCommitIndex := r.getCommitIndex() | |||
| commitIndex := r.leaderState.commitment.getCommitIndex() | |||
| r.setCommitIndex(commitIndex) | |||
| leadershipAsserted = true | |||
There was a problem hiding this comment.
I'm not 100% this is correct, I'd like some advice. What we're really trying to do here is catch when the Noop log entry generated here makes it to this point in the code i.e. when the Noop log entry is committed.
|
Would you appreciate any help on the test failure, don't immediately see how it could be related to this change. |
|
Looks like a racy test, passes now. Any input on this PR? |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Potential fix for #621
This allows clients of this library to check if the current node, assuming it is the Leader, has explicitly asserted leadership in the current term. "Asserting" is defined has having committed at least one log entry in the current term, as per the Raft paper.
This change adds a new channel, which is only serviced when in Leadership mode. This channel will respond with the asserted status via a Future. Clients are recommended to call this function only until they have confirmed that the leadership has been asserted. Once asserted for a given term the state can be cached until the end of the term.
This code is necessary to properly implement the Read Optimization outlined in the Raft paper and dissertation. The dissertation explains that it is not sufficient to simply check the Leader's commit index. Instead a client must first confirm that the Leader has explicitly asserted leadership by committing a log entry in the current term. Only then is commit index valid.