[CASSANDRA-16364] Joining nodes simultaneously with auto_bootstrap:false can cause token collision

• Type: Bug
• Status: Open
• Priority: Normal
• Resolution: Unresolved
• Fix Version/s: 4.0.x
• Component/s: Cluster/Membership
• Bug Category: Correctness - Consistency
• Severity: Normal
• Complexity: Normal
• Discovered By: User Report
• Platform: All
• Assignee: Unassigned
• Reporter: Paulo Motta

Reviewers

Michael Semb Wever

• Created: 19/Dec/20 22:53
• Updated: 08/Apr/24 19:15

Description

While raising a 6-node ccm cluster to test 4.0-beta4, 2 nodes chosen the same tokens using the default allocate_tokens_for_local_rf. However they both succeeded bootstrap with colliding tokens.

We were familiar with this issue from CASSANDRA-13701 and CASSANDRA-16079, and the workaround to fix this is to avoid parallel bootstrap when using allocate_tokens_for_local_rf.

However, since this is the default behavior, we should try to detect and prevent this situation when possible, since it can break users relying on parallel bootstrap behavior.

I think we could prevent this as following:
1. announce intent to bootstrap via gossip (ie. add node on gossip without token information)
2. wait for gossip to settle for a longer period (ie. ring delay)
3. allocate tokens (if multiple bootstrap attempts are detected, tie break via node-id)
4. broadcast tokens and move on with bootstrap

Issue Links

• is caused by: CASSANDRA-13701 Lower default num_tokens