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From Carl Mueller <carl.muel...@smartthings.com.INVALID>
Subject Re: postmortem on 2.2.13 scale out difficulties
Date Wed, 12 Jun 2019 16:36:37 GMT
We're getting

DEBUG [GossipStage:1] 2019-06-12 15:20:07,797 MigrationManager.java:96 -
Not pulling schema because versions match or shouldPullSchemaFrom returned
false

multiple times, as it contacts the nodes.

On Wed, Jun 12, 2019 at 11:35 AM Carl Mueller <carl.mueller@smartthings.com>
wrote:

> We only were able to scale out four nodes and then failures started
> occurring, including multiple instances of nodes joining a cluster without
> streaming.
>
> Sigh.
>
> On Tue, Jun 11, 2019 at 3:11 PM Carl Mueller <carl.mueller@smartthings.com>
> wrote:
>
>> We had a three-DC (asia-tokyo/europe/us) cassandra 2.2.13 cluster, AWS,
>> IPV6
>>
>> Needed to scale out the asia datacenter, which was 5 nodes, europe and us
>> were 25 nodes
>>
>> We were running into bootstrapping issues where the new node failed to
>> bootstrap/stream, it failed with
>>
>> "java.lang.RuntimeException: A node required to move the data
>> consistently is down"
>>
>> ...even though they were all up based on nodetool status prior to adding
>> the node.
>>
>> First we increased the phi_convict_threshold to 12, and that did not
>> help.
>>
>> CASSANDRA-12281 appeared similar to what we had problems with, but I
>> don't think we hit that. Somewhere in there someone wrote
>>
>> "For us, the workaround is either deleting the data (then bootstrap
>> again), or increasing the ring_delay_ms. And the larger the cluster is, the
>> longer ring_delay_ms is needed. Based on our tests, for a 40 nodes cluster,
>> it requires ring_delay_ms to be >50seconds. For a 70 nodes cluster,
>> >100seconds. Default is 30seconds."
>>
>> Given the WAN nature or our DCs, we used ring_delay_ms to 100 seconds and
>> it finally worked.
>>
>> side note:
>>
>> During the rolling restarts for setting phi_convict_threshold we observed
>> quite a lot of status map variance between nodes (we have a program to poll
>> all of a datacenter or cluster's view of the gossipinfo and statuses. AWS
>> appears to have variance in networking based on the phi_convict_threshold
>> advice, I'm not sure if our difficulties were typical in that regard and/or
>> if our IPV6 and/or globally distributed datacenters were exacerbating
>> factors.
>>
>> We could not reproduce this in loadtest, although loadtest is only eu and
>> us (but is IPV6)
>>
>

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