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

["Jon Haddad (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-16364?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17847460#comment-17847460 ] 

Jon Haddad commented on CASSANDRA-16364:
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I think we should apply some randomness to the tokens to ensure that even in the case of 1 nodes starting at once, it's still unlikely that they will ever have a conflict.  Applying a random() value to the token value between - 2^8 and 2^8 makes this statistically very, very unlikely that we'll ever have a collision while also preserving the balance of token distribution in the ring.  In the case of 2 nodes starting at the same time, the operator will have weird token distribution instead of data loss.

> Joining nodes simultaneously with auto_bootstrap:false can cause token collision
> --------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-16364
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-16364
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Cluster/Membership
>            Reporter: Paulo Motta
>            Priority: Normal
>             Fix For: 4.0.x, 4.1.x, 5.0.x, 5.x
>
>
> 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



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