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From Erick Erickson <erickerick...@gmail.com>
Subject Re: solrcloud replicas not in sync
Date Wed, 24 May 2017 15:37:23 GMT
By default, enough closed log files will be kept to hold the last 100
documents indexed. This is for "peer sync" purposes. Say replica1 goes
offline for a bit. When it comes back online, if it's fallen behind by
no more than 100 docs, the docs are replayed from another replica's
tlog.

Having such tiny tlogs is kind of unusual. My guess is that your
ingestion rate is quite low. Every time a hard commit happens, a new
tlog is opened up and the old one is closed. Having such tiny tlogs
implies that you are getting one or a few documents per autocommit
interval, so each tlog contains just a few docs. There's nothing wrong
with that, mind you, so it's not a problem.

When do log files get deleted? It Depends (tm). In the non-CDCR case,
if the most recent N closed tlogs contain 100 or more documents, the
tlogs older than N are deleted.

In the CDCR case, the above condition must be true _and_ the docs in
tlogs older than N must have been transmitted to the target cluster.

Best,
Erick

On Wed, May 24, 2017 at 8:27 AM, Webster Homer <webster.homer@sial.com> wrote:
> The tlog sizes are strange
> In the case of the collection where we had issues with the replicas the
> tlog sizes are 740 bytes and 938 bytes on the target side and the same on
> the source side. There are a lot of them on the source side, when do tlog
> files get deleted?
>
>
>
> On Tue, May 23, 2017 at 12:52 PM, Erick Erickson <erickerickson@gmail.com>
> wrote:
>
>> This is all quite strange. Optimize (BTW, it's rarely
>> necessary/desirable on an index that changes, despite its name)
>> shouldn't matter here. CDCR forwards the raw documents to the target
>> cluster.
>>
>> Ample time indeed. With a soft commit of 15 seconds, that's your
>> window (with some slop for how long CDCR takes).
>>
>> If you do a search and sort by your timestamp descending, what do you
>> see on the target cluster? And when you are indexing and CDCR is
>> running, your target cluster solr logs should show updates coming in.
>> Mostly checking if the data is even getting to the target cluster
>> here.
>>
>> Also check the tlogs on the source cluster. By "check" here I just
>> mean "are they reasonable size", and "reasonable" should be very
>> small. The tlogs are the "queue" that CDCR uses to store docs before
>> forwarding to the target cluster, so this is just a sanity check. If
>> they're huge, then CDCR is not forwarding anything to the target
>> cluster.
>>
>> It's also vaguely possible that
>> IgnoreCommitOptimizeUpdateProcessorFactory is interfering, if so it's
>> a bug and should be reported as a JIRA. If you remove that on the
>> target cluster, does the behavior change?
>>
>> I'm mystified here as you can tell.
>>
>> Best,
>> Erick
>>
>> On Tue, May 23, 2017 at 10:12 AM, Webster Homer <webster.homer@sial.com>
>> wrote:
>> > We see a pretty consistent issue where the replicas show in the admin
>> > console as not current, indicating that our auto commit isn't commiting.
>> In
>> > one case we loaded the data to the source, cdcr replicated it to the
>> > targets and we see the source and the target as having current = false.
>> It
>> > is searchable so the soft commits are happening. We turned off data
>> loading
>> > to investigate this issue, and the replicas are still not current after 3
>> > days. So there should have been ample time to catch up.
>> > This is our autoCommit
>> >      <autoCommit>
>> >        <maxDocs>25000</maxDocs>
>> >        <maxTime>${solr.autoCommit.maxTime:300000}</maxTime>
>> >        <openSearcher>false</openSearcher>
>> >      </autoCommit>
>> >
>> > This is our autoSoftCommit
>> >      <autoSoftCommit>
>> >        <maxTime>${solr.autoSoftCommit.maxTime:15000}</maxTime>
>> >      </autoSoftCommit>
>> > neither property, solr.autoCommit.maxTime or solr.autoSoftCommit.maxTime
>> > are set.
>> >
>> > We also have an updateChain that calls the
>> > solr.IgnoreCommitOptimizeUpdateProcessorFactory to ignore client
>> commits.
>> > Could that be the cause of our
>> >       <updateRequestProcessorChain name="cleanup">
>> >      <!-- Ignore commits from clients, telling them all's OK -->
>> >        <processor class="solr.IgnoreCommitOptimizeUpdateProc
>> essorFactory">
>> >          <int name="statusCode">200</int>
>> >        </processor>
>> >
>> >        <processor class="TrimFieldUpdateProcessorFactory" />
>> >        <processor class="RemoveBlankFieldUpdateProcessorFactory" />
>> >
>> >        <processor class="solr.LogUpdateProcessorFactory" />
>> >        <processor class="solr.RunUpdateProcessorFactory" />
>> >      </updateRequestProcessorChain>
>> >
>> > We did create a date field to all our collections that defaults to NOW
>> so I
>> > can see that no new data was added, but the replicas don't seem to get
>> the
>> > commit. I assume this is something in our configuration (see above).
>> >
>> > Is there a way to determine when the last commit occurred?
>> >
>> > I believe that the one replica got out of sync due to an admin running an
>> > optimize while cdcr was still running.
>> > That was one collection, but it looks like we are missing commits on most
>> > of our collections.
>> >
>> > Any help would be greatly appreciated!
>> >
>> > Thanks,
>> > Webster Homer
>> >
>> > On Mon, May 22, 2017 at 4:12 PM, Erick Erickson <erickerickson@gmail.com
>> >
>> > wrote:
>> >
>> >> You can ping individual replicas by addressing to a specific replica
>> >> and setting distrib=false, something like
>> >>
>> >>      http://SOLR_NODE:port/solr/collection1_shard1_replica1/
>> >> query?distrib=false&q=......
>> >>
>> >> But one thing to check first is that you've committed. I'd:
>> >> 1> turn off indexing on the source cluster.
>> >> 2> wait until the CDCR had caught up (if necessary).
>> >> 3> issue a hard commit on the target
>> >> 4> _then_ see if the counts were what is expected.
>> >>
>> >> Due to the fact that autocommit settings can fire at different clock
>> >> times even for replicas on the same shard, it's easier to track
>> >> whether it's a transient issue. The other thing I've seen people do is
>> >> have a timestamp on the docs set to NOW (there's an update processor
>> >> that can do this). Then when you check for consistency you can use
>> >> fq=timestamp:[* TO NOW - (some interval significantly longer than your
>> >> autocommit interval)].
>> >>
>> >> bq: Is there a way to recover when a shard has inconsistent replicas.
>> >> If I use the delete replica API call to delete one of them and then use
>> add
>> >> replica to create it from scratch will it auto-populate from the other
>> >> replica in the shard?
>> >>
>> >> Yes. Whenever you ADDREPLICA it'll catch itself up from the leader
>> >> before becoming active. It'll have to copy the _entire_ index from the
>> >> leader, so you'll see network traffic spike.
>> >>
>> >> Best,
>> >> Erick
>> >>
>> >> On Mon, May 22, 2017 at 1:41 PM, Webster Homer <webster.homer@sial.com>
>> >> wrote:
>> >> > I have a solrcloud collection with 2 shards and 4 replicas. The
>> replicas
>> >> > for shard 1 have different numbers of records, so different queries
>> will
>> >> > return different numbers of records.
>> >> >
>> >> > I am not certain how this occurred, it happened in a collection that
>> was
>> >> a
>> >> > cdcr target.
>> >> >
>> >> > Is there a way to limit a search to a specific replica of a shard?
We
>> >> want
>> >> > to understand the differences
>> >> >
>> >> > Is there a way to recover when a shard has inconsistent replicas.
>> >> > If I use the delete replica API call to delete one of them and then
>> use
>> >> add
>> >> > replica to create it from scratch will it auto-populate from the other
>> >> > replica in the shard?
>> >> >
>> >> > Thanks,
>> >> > Webster
>> >> >
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>
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> notify the sender immediately and delete the message and any attachment
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> subsidiaries do not accept liability for any omissions or errors in this
> message which may arise as a result of E-Mail-transmission or for damages
> resulting from any unauthorized changes of the content of this message and
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> not accept liability for any damages caused by any virus transmitted
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