[ZOOKEEPER-901] Redesign of QuorumCnxManager

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.3.1
• Component/s: leaderElection
• Assignee: Michael Han
• Reporter: Flavio Paiva Junqueira
• Created: 17/Oct/10 13:09
• Updated: 03/Feb/22 08:50

Description

QuorumCnxManager manages TCP connections between ZooKeeper servers for leader election in replicated mode. We have identified over time a couple of deficiencies that we would like to fix. Unfortunately, fixing these issues requires a little more than just generating a couple of small patches. More specifically, I propose, based on previous discussions with the community, that we reimplement QuorumCnxManager so that we achieve the following:

1. Establishing connections should not be a blocking operation, and perhaps even more important, it shouldn't prevent the establishment of connections with other servers;
2. Using a pair of threads per connection is a little messy, and we have seen issues over time due to the creation and destruction of such threads. A more reasonable approach is to have a single thread and a selector.

Issue Links

• blocks: ZOOKEEPER-2080 Fix deadlock in dynamic reconfiguration
• relates to: ZOOKEEPER-900 FLE implementation should be improved to use non-blocking sockets