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From Erick Erickson <erickerick...@gmail.com>
Subject Re: Fully automated replica creation in AWS
Date Wed, 09 Dec 2015 19:19:00 GMT
Not that I know of. The two systems are somewhat disconnected.
AWS doesn't know that Solr lives on those nodes, it's just spinning
one up, right? Albeit with Solr running.

There's nothing in Solr that auto-detects the  existence of a new
Solr node and automagically assigns collections and/or replicas.

How would either system intuit that this new node is replacing
something else and "do the right thing"?

I'll tell you how, by interrogating Zookeeper and seeing that for some
specific collection, shardX had fewer replicas than other shards and
issuing the Collections API ADDREPLICA command.

But now there are _three_ systems that need to be coordinated and
doing the right thing in your situation would be the wrong thing in
another. The last thing many sys ops want is having replicas started
without their knowledge.

And on top of that, I have doubts about the model. Having AWS
elastically spin up a new replica is a heavyweight operation from
Solr's perspective. I mean this potentially copies a many G set of
index files from one place to another which could take a long time,
is that really what's desired here?

I have seen some folks spin up/down Solr instances based on a
schedule if they know roughly when the peak load will be, but again
there's nothing built in to handle this.

Best,
Erick

On Wed, Dec 9, 2015 at 10:15 AM, Ugo Matrangolo
<ugo.matrangolo@gmail.com> wrote:
> Hi,
>
> I was trying to setup a SolrCloud cluster in AWS backed by an ASG (auto
> scaling group) serving a replicated collection. I have just came across a
> case when one of the Solr node became unresponsive with AWS killing it and
> spinning a new one.
>
> Unfortunately, this new Solr node did not join as a replica of the existing
> collection requiring human intervention to configure it as a new replica.
>
> I was wondering if there is around something that will make this process
> fully automated by detecting that a new node just joined the cluster and
> instructing it (e.g. via Collections API) to join as a replica of a given
> collection.
>
> Best
> Ugo

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