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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4127) migration support for vnodes
Date Wed, 11 Jul 2012 18:23:34 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4127?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13411809#comment-13411809
] 

Jonathan Ellis commented on CASSANDRA-4127:
-------------------------------------------

bq. This will allow a rolling migration where N new hosts are bootstrapped into the cluster
(with num_tokens set appropriately) and then the N old nodes are decommissioned.

That's a fairly painful / expensive proposition.

Since we already have vnode migration for bootstrap / decommission, couldn't we just add a
{{nodetool shuffle}} command to do that in-place instead?
                
> migration support for vnodes
> ----------------------------
>
>                 Key: CASSANDRA-4127
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4127
>             Project: Cassandra
>          Issue Type: Sub-task
>          Components: Core
>            Reporter: Sam Overton
>            Assignee: Sam Overton
>              Labels: vnodes
>
> If, when starting up for the first time, the host only has 1 token but num_tokens is
configured differently, then this will trigger a migration process:
> * The host will assign itself num_tokens tokens in its own range
> * The new tokens will be gossiped
> This will allow a rolling migration where N new hosts are bootstrapped into the cluster
(with num_tokens set appropriately) and then the N old nodes are decommissioned. This will
result in even distribution of the data among the new nodes with randomly assigned tokens.
> _Edit0: Appended patch information._
> h3. Patches
> ||Compare||Raw diff||Description||
> |[01_migration_path|https://github.com/acunu/cassandra/compare/top-bases/p/4127/01_migration_path...p/4127/01_migration_path]|[01_migration_path.patch|https://github.com/acunu/cassandra/compare/top-bases/p/4127/01_migration_path...p/4127/01_migration_path.diff]|Migrate
from one token to many|
> ----
> _Note: These are branches managed with TopGit. If you are applying the patch output manually,
you will either need to filter the TopGit metadata files (i.e. {{wget -O - <url> | filterdiff
-x*.topdeps -x*.topmsg | patch -p1}}), or remove them afterward ({{rm .topmsg .topdeps}})._

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