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From "Brandon Williams (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6127) vnodes don't scale to hundreds of nodes
Date Wed, 06 Nov 2013 22:26:18 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6127?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13815379#comment-13815379
] 

Brandon Williams commented on CASSANDRA-6127:
---------------------------------------------

At this point, I think we should:

* see if the flapping happens with vnodes (maybe Quentin already knows from his last test)
* see if the flapping happens without vnodes but the same number of nodes

Because if sum() in ArrivalWindow is burning the most CPU in the Gossiper task (note: not
bottlenecking, each call was at most ~3ms, there were just lots of them) then that means that
the problem is no longer tied to vnodes (if it ever was, since sum is per-node, not per-token)
and we should probably open a new ticket (can't start a cluster of size >=X all at once,
or similar) and discuss there.  We know that clusters much larger than any discussed on this
ticket exist, but I don't think any of them have all rebooted at once.

> vnodes don't scale to hundreds of nodes
> ---------------------------------------
>
>                 Key: CASSANDRA-6127
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6127
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: Any cluster that has vnodes and consists of hundreds of physical
nodes.
>            Reporter: Tupshin Harper
>            Assignee: Jonathan Ellis
>         Attachments: 6000vnodes.patch, AdjustableGossipPeriod.patch, delayEstimatorUntilStatisticallyValid.patch
>
>
> There are a lot of gossip-related issues related to very wide clusters that also have
vnodes enabled. Let's use this ticket as a master in case there are sub-tickets.
> The most obvious symptom I've seen is with 1000 nodes in EC2 with m1.xlarge instances.
Each node configured with 32 vnodes.
> Without vnodes, cluster spins up fine and is ready to handle requests within 30 minutes
or less. 
> With vnodes, nodes are reporting constant up/down flapping messages with no external
load on the cluster. After a couple of hours, they were still flapping, had very high cpu
load, and the cluster never looked like it was going to stabilize or be useful for traffic.



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