[RATIS-2174] Move future.join outside the lock

• Type: Wish
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.1.1
• Fix Version/s: 3.2.0
• Component/s: server
• Assignee: yuuka
• Reporter: yuuka
• Created: 16/Oct/24 01:34
• Updated: 21/Oct/24 18:31
• Resolved: 21/Oct/24 18:28

Description

 
In RATIS-2162, we solved a deadlock problem, but after observing for a few days, there may still be potential deadlock problems elsewhere.
 
The main reason for deadlock is to hold a lock and wait for a future.
 
So I suggest waiting for the future outside the lock as much as possible, which should avoid deadlocks
 

Currently, I found that calling changeToFollower in the following functions causes the above situation:

1. RaftServerImpl.appendEntries
2. RaftServerImpl.RequestVote
3. checkAndInstallSnapshot

Issue Links

• links to: GitHub Pull Request #1168