procedure to restart solrcloud, and config/collection consistency

[xavier jmlucjav <jm...@gmail.com>]

Hi,

When I need to restart a Solrcloud cluster, I always do this:
- log in into host nb1, stop solr
- log in into host nb2, stop solr
-...
- log in into host nbX, stop solr
- verify all hosts did stop
- in host nb1, start solr
- in host nb12, start solr
-...

I always wondered, if this was not really needed, and I could just call
'restart' in every node, in a quick loop, and forget about it. Does anyone
know if this is the case?

My doubt is in regards to changing some config, and then doing the above
(just restart nodes in a loop). For example, what if I change a config G
used in collection C, and I restart just one of the nodes (N1), leaving the
rest alone. If all the nodes contain a shard for C, what happens, N1 is
using the new config and the rest are not? how is this handled?

thanks
xavier

Re: procedure to restart solrcloud, and config/collection consistency

[xavier jmlucjav <jm...@gmail.com>]

hi Shawn,

as I replied to Markus, of course I know (and use) the collections api to
reload the config. I am asking what would happen in that scenario:
 - config updated (but collection not reloaded)
 - i restart one node
now one node has the new config and the rest the old one??

To which he already replied:
>The restared/reloaded node has the new config, the others have the old
config until reloaded/restarted.

I was not asking about making solr restart itself, my English must be worst
than I thought. By the way, stuff like that can be achieved with
http://yajsw.sourceforge.net/ a very powerful java wrapper, I used to use
it when Solr did not have a built in daemon setup. It was built by someone
how was using JSW, and got pissed when that one went commercial. It is very
configurable, but of course more complex. I wrote something about it some
time ago
https://medium.com/@jmlucjav/how-to-install-solr-as-a-service-in-any-platform-including-solr-5-8e4a93cc3909

thanks

On Thu, Feb 9, 2017 at 4:53 PM, Shawn Heisey <ap...@elyograg.org> wrote:

> On 2/9/2017 5:24 AM, xavier jmlucjav wrote:
> > I always wondered, if this was not really needed, and I could just call
> > 'restart' in every node, in a quick loop, and forget about it. Does
> anyone
> > know if this is the case?
> >
> > My doubt is in regards to changing some config, and then doing the above
> > (just restart nodes in a loop). For example, what if I change a config G
> > used in collection C, and I restart just one of the nodes (N1), leaving
> the rest alone. If all the nodes contain a shard for C, what happens, N1 is
> using the new config and the rest are not? how is this handled?
>
> If you want to change the config or schema for a collection and make it
> active across all nodes, just use the collections API to RELOAD the
> collection.  The change will be picked up everywhere.
>
> https://cwiki.apache.org/confluence/display/solr/Collections+API
>
> To answer your question: No.  Solr does not have the ability to restart
> itself.  It would require significant development effort and a
> fundamental change in how Solr is started to make it possible.  It is
> something that has been discussed, but at this time it is not possible.
>
> One idea that would make this possible is mentioned on the following
> wiki page.  It talks about turning Solr into two applications instead of
> one:
>
> https://wiki.apache.org/solr/WhyNoWar#Information_that.27s_
> not_version_specific
>
> Again -- it would not be easy, which is why it hasn't been done yet.
>
> Thanks,
> Shawn
>
>

Re: procedure to restart solrcloud, and config/collection consistency

[Shawn Heisey <ap...@elyograg.org>]

On 2/9/2017 5:24 AM, xavier jmlucjav wrote:
> I always wondered, if this was not really needed, and I could just call
> 'restart' in every node, in a quick loop, and forget about it. Does anyone
> know if this is the case?
>
> My doubt is in regards to changing some config, and then doing the above
> (just restart nodes in a loop). For example, what if I change a config G
> used in collection C, and I restart just one of the nodes (N1), leaving the rest alone. If all the nodes contain a shard for C, what happens, N1 is using the new config and the rest are not? how is this handled?

If you want to change the config or schema for a collection and make it
active across all nodes, just use the collections API to RELOAD the
collection.  The change will be picked up everywhere.

https://cwiki.apache.org/confluence/display/solr/Collections+API

To answer your question: No.  Solr does not have the ability to restart
itself.  It would require significant development effort and a
fundamental change in how Solr is started to make it possible.  It is
something that has been discussed, but at this time it is not possible.

One idea that would make this possible is mentioned on the following
wiki page.  It talks about turning Solr into two applications instead of
one:

https://wiki.apache.org/solr/WhyNoWar#Information_that.27s_not_version_specific

Again -- it would not be easy, which is why it hasn't been done yet.

Thanks,
Shawn