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From "Brandon Williams (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-4119) Support multiple non-consecutive tokens per host (virtual nodes)
Date Thu, 21 Jun 2012 18:45:43 GMT


Brandon Williams commented on CASSANDRA-4119:

It's been some time since I last tested this, so I decided to give it another go.  After updating
the branch to 7e9ecd9783fbefaea13fe1b1ceb3bac46aa57291 I'm unable to reproduce, so perhaps
it was some condition in trunk exacerbating the problem that has been fixed in the past ~20
> Support multiple non-consecutive tokens per host (virtual nodes)
> ----------------------------------------------------------------
>                 Key: CASSANDRA-4119
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Sam Overton
>            Assignee: Sam Overton
>              Labels: virtualnodes, vnodes
> This is the parent ticket for the virtual nodes implementation which was proposed here: and discussed in the subsequent
> The goals of this ticket are:
> * reduced operations complexity for scaling up/down
> * reduced rebuild time in event of failure
> * evenly distributed load impact in the event of failure
> * evenly distributed impact of streaming operations
> * more viable support for heterogeneity of hardware
> The intention is that this can be done in a way which is
> * fully backwards-compatible
> * optionally enabled
> The latter of these can be trivially achieved by setting the number of tokens per host
to 1, to reproduce the existing behaviour.
> Implementation detail can be added and discussed in the sub-tickets, but here is an overview
of the proposed changes:
> * TokenMetadata will allow multiple tokens per host
> * Hosts will be referred to by a UUID instead of token (e.g. in Gossip, when storing
hints, etc.)
> * A bootstrapping node can get multiple tokens from initial_token (comma separated) or
by random allocation
> * NetworkTopologyStrategy will be extended to be aware of virtual nodes so that replicas
are not placed on the same host (similar to racks now)
> * Repairs will be staggered similar to CASSANDRA-3721
> * Nodetool operations will be virtual-node aware, while maintaining backwards compatibility
(ie. existing scripts won't have to change)
> * Upgrade will be a standard rolling upgrade, with optional rolling migration to full
vnode support

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