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Date: Thu, 1 Sep 2011 09:10:58 -0500
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Subject: Re: Solr commit process and read downtime
From: Mike Austin <mike.austin@juggle.com>
To: solr-user@lucene.apache.org
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Wow.. thanks for the great answers Erick!  This answered my concerns
perfectly.

Mike

On Thu, Sep 1, 2011 at 7:54 AM, Erick Erickson <erickerickson@gmail.com>wrote:

> See below:
>
> On Wed, Aug 31, 2011 at 2:16 PM, Mike Austin <mike.austin@juggle.com>
> wrote:
> > I've set up a master slave configuration and it's working great!  I know
> > this is the better setup but if I had just one index due to requirements,
> > I'd like to know more about the performance hit of the commit. let's just
> > assume I have a decent size index of a few gig normal sized documents
> with
> > high traffic.  A few questions:
> >
> > - (main question) When you do a commit on a single index, is there
> anytime
> > when the reads will not have an index to search on?
> No. While the new searcher is warming up, all incoming searches are
> handled by the old searcher. When the new searcher is warmed up,
> new requests are routed to it, and when the last search is completed
> in the old searcher, it's shut down
>
> > - With the rebuilding of caches and whatever else happens, is the only
> > downside the fact that the server performance will be degraded due to
> file
> > copy, cache warming, etc.. or will the index be actually locked at some
> > point?
> The index will not be locked, if by locked you mean the searches will
> not happen. See above. The server will certainly have more work to
> do, and if you're running close to the limits you might notice some
> slowdown. But often there is no noticeable pause. Note that while
> all this goes on, you will have *two* copies of the caches etc. in
> memory...
>
> > - On a commit, do the files get copied so you need double the space or is
> > that just the optimize?
> You have to allow for the relatively rare instance when the merge
> process combines all your segments into one, which will require
> at least double the disk space. Optimize guarantees this
> will happen, but it can (and will) happen on commit occasionally.
>
> >
> > I know a master/slave setup is used to reduce these issues, but if I had
> > only one server I need to know the potential risks.
> Well, you're just putting lots of stuff on a server. Solr will quite
> happily deal
> with this situation and, depending upon how much traffic you have and
> your machine's size, this may be fine. Do be aware of the "warmup hell"
> problem and don't commit too frequently or your warming searchers
> may tie their knickers in a knot.
>
> And one risk in this setup is that you have no way to quickly bring up
> a server if your one machine crashes, you have to re-index *all* your data.
>
> Best
> Erick
>
> >
> > Thanks,
> > Mike
> >
>

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