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From Erick Erickson <erickerick...@gmail.com>
Subject Re: solrcloud Auto-commit doesn't seem reliable
Date Mon, 12 Feb 2018 23:00:02 GMT
bq: But if 3 seconds is aggressive what would be a  good value for soft commit?

The usual answer is "as long as you can stand". All top-level caches are
invalidated, autowarming is done etc. on each soft commit. That can be a lot of
work and if your users are comfortable with docs not showing up for,
say, 10 minutes
then use 10 minutes. As always "it depends" here, the point is not to
do unnecessary
work if possible.

bq: If a commit doesn't happen how would there ever be an index merge
that would remove the deleted documents.

Right, it wouldn't. It's a little more subtle than that though.
Segments on various
replicas will contain different docs, thus the term/doc statistics can be a bit
different between multiple replicas. None of the stats will change
until the commit
though. You might try turning no distributed doc/term stats though.

Your comments about PULL or TLOG replicas are well taken. However, even those
won't be absolutely in sync since they'll replicate from the master at slightly
different times and _could_ get slightly different segments _if_
there's indexing
going on. But let's say you stop indexing. After the next poll
interval all the replicas
will have identical characteristics and will score the docs the same.

I don't have any signifiant wisdom to offer here, except this is really the
first time I've heard of this behavior. About all I can imagine is
that _somehow_
the soft commit interval is -1. When you say you "issue a commit" I'm assuming
it's via ....collection/update?commit=true or some such which issues a hard
commit with openSearcher=true. And it's on a _collection_ basis, right?

Sorry I can't be more help
Erick




On Mon, Feb 12, 2018 at 10:44 AM, Webster Homer <webster.homer@sial.com> wrote:
> Erick, I am aware of the CDCR buffering problem causing tlog retention, we
> always turn buffering off in our cdcr configurations.
>
> My post was precipitated by seeing that we had uncommitted data in
> collections > 24 hours after it was loaded. The collections I was looking
> at are in our development environment, where we do not use CDCR. However
> I'm pretty sure that I've seen situations in production where commits were
> also long overdue.
>
> the "autoSoftcommit" was a typo. The soft commit logic seems to be fine, I
> don't see an issue with data visibility. But if 3 seconds is aggressive
> what would be a  good value for soft commit? We have a couple of
> collections that are updated every minute although most of them are updated
> much less frequently.
>
> My reason for raising this commit issue is that we see problems with the
> relevancy of solrcloud searches, and the NRT replica type. Sometimes the
> results flip where the best hit varies by what replica serviced the search.
> This is hard to explain to management. Doing an optimized does address the
> problem for a while. I try to avoid optimizing for the reasons you and Sean
> list. If a commit doesn't happen how would there ever be an index merge
> that would remove the deleted documents.
>
> The problem with deletes and relevancy don't seem to occur when we use TLOG
> replicas, probably because they don't do their own indexing but get copies
> from their leader. We are testing them now eventually we may abandon the
> use of NRT replicas for most of our collections.
>
> I am quite concerned about this commit issue. What kinds of things would
> influence whether a commit occurs? One commonality for our systems is that
> they are hosted in a Google cloud. We have a number of collections that
> share configurations, but others that do not. I think commits do happen,
> but I don't trust that autoCommit is reliable. What can we do to make it
> reliable?
>
> Most of our collections are reindexed weekly with partial updates applied
> daily, that at least is what happens in production, our development clouds
> are not as regular.
>
> Our solr startup script sets the following values:
> -Dsolr.autoCommit.maxDocs=35000
> -Dsolr.autoCommit.maxTime=60000
> -Dsolr.autoSoftCommit.maxTime=3000
>
> I don't think we reference  solr.autoCommit.maxDocs in our solrconfig.xml
> files.
>
> here are our settings for autoCommit and autoSoftCommit
>
> We had a lot of issues with missing commits when we didn't set
> solr.autoCommit.maxTime
>      <autoCommit>
>        <maxTime>${solr.autoCommit.maxTime:60000}</maxTime>
>        <openSearcher>false</openSearcher>
>     </autoCommit>
>
>      <autoSoftCommit>
>        <maxTime>${solr.autoSoftCommit.maxTime:5000}</maxTime>
>      </autoSoftCommit>
>
>
>
> On Fri, Feb 9, 2018 at 3:49 PM, Shawn Heisey <apache@elyograg.org> wrote:
>
>> On 2/9/2018 9:29 AM, Webster Homer wrote:
>>
>>> A little more background. Our production Solrclouds are populated via
>>> CDCR,
>>> CDCR does not replicate commits, Commits to the target clouds happen via
>>> autoCommit settings
>>>
>>> We see relvancy scores get inconsistent when there are too many deletes
>>> which seems to happen when hard commits don't happen.
>>>
>>> On Fri, Feb 9, 2018 at 10:25 AM, Webster Homer <webster.homer@sial.com>
>>> wrote:
>>>
>>> I we do have autoSoftcommit set to 3 seconds. It is NOT the visibility of
>>>> the records that is my primary concern. I am concerned about is the
>>>> accumulation of uncommitted tlog files and the larger number of deleted
>>>> documents.
>>>>
>>>
>> For the deleted documents:  Have you ever done an optimize on the
>> collection?  If so, you're going to need to re-do the optimize regularly to
>> keep deleted documents from growing out of control.  See this issue for a
>> very technical discussion about it:
>>
>> https://issues.apache.org/jira/browse/LUCENE-7976
>>
>> Deleted documents probably aren't really related to what we've been
>> discussing.  That shouldn't really be strongly affected by commit settings.
>>
>> -----
>>
>> A 3 second autoSoftCommit is VERY aggressive.   If your soft commits are
>> taking longer than 3 seconds to complete, which is often what happens, then
>> that will lead to problems.  I wouldn't expect it to cause the kinds of
>> problems you describe, though.  It would manifest as Solr working too hard,
>> logging warnings or errors, and changes taking too long to show up.
>>
>> Assuming that the config for autoSoftCommit doesn't have the typo that
>> Erick mentioned.
>>
>> ----
>>
>> I have never used CDCR, so I know very little about it.  But I have seen
>> reports on this mailing list saying that transaction logs never get deleted
>> when CDCR is configured.
>>
>> Below is a link to a mailing list discussion related to CDCR not deleting
>> transaction logs.  Looks like for it to work right a buffer needs to be
>> disabled, and there may also be problems caused by not having a complete
>> zkHost string in the CDCR config:
>>
>> http://lucene.472066.n3.nabble.com/CDCR-how-to-deal-with-
>> the-transaction-log-files-td4345062.html
>>
>> Erick also mentioned this.
>>
>> Thanks,
>> Shawn
>>
>
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