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From Erick Erickson <erickerick...@gmail.com>
Subject Re: Questions on SolrCloud core state, when will Solr recover a "DOWN" core to "ACTIVE" core.
Date Fri, 29 Apr 2016 14:52:04 GMT
Well, there have been lots of improvements since 4.6. You're right,
logically when things come back up and are all reachable, it seems
like it is theoretically possible to bring a node back up. There
have been situations where that doesn't happen, and various fixes
have been implemented to fix them as they're identified....

You might try reloading the core from the core admin (that's
about the only thing you should try in SolrCloud from the
core admin screen)....

Best,
Erick

On Wed, Apr 27, 2016 at 10:58 AM, Li Ding <li.ding@bloomreach.com> wrote:
> Hi Erick,
>
> I don't have the GC log.  But after the GC finished.  Isn't zk ping
> succeeds and the core should be back to normal state?  From the log I
> posted.  The sequence is:
>
> 1) Solr Detects itself can't connect to ZK and reconnect to ZK
> 2) Solr marked all cores are down
> 3) Solr recovery each cores, some succeeds, some failed.
> 4) After 30 minutes, the cores that are failed still marked as down.
>
> So my questions is, during the 30 minutes interval, if GC takes too long,
> all cores should failed.  And GC doesn't take longer than a minute since
> all serving requests to other calls succeeds and the next zk ping should
> bring the core back to normal? right?  We have an active monitor running at
> the same time querying every core in distrib=false mode and every query
> succeeds.
>
> Thanks,
>
> Li
>
> On Tue, Apr 26, 2016 at 6:20 PM, Erick Erickson <erickerickson@gmail.com>
> wrote:
>
>> One of the reasons this happens is if you have very
>> long GC cycles, longer than the Zookeeper "keep alive"
>> timeout. During a full GC pause, Solr is unresponsive and
>> if the ZK ping times out, ZK assumes the machine is
>> gone and you get into this recovery state.
>>
>> So I'd collect GC logs and see if you have any
>> stop-the-world GC pauses that take longer than the ZK
>> timeout.
>>
>> see Mark Millers primer on GC here:
>> https://lucidworks.com/blog/2011/03/27/garbage-collection-bootcamp-1-0/
>>
>> Best,
>> Erick
>>
>> On Tue, Apr 26, 2016 at 2:13 PM, Li Ding <li.ding@bloomreach.com> wrote:
>> > Thank you all for your help!
>> >
>> > The zookeeper log rolled over, thisis from Solr.log:
>> >
>> > Looks like the solr and zk connection is gone for some reason
>> >
>> > INFO  - 2016-04-21 12:37:57.536;
>> > org.apache.solr.common.cloud.ConnectionManager; Watcher
>> > org.apache.solr.common.cloud.ConnectionManager@19789a96
>> > name:ZooKeeperConnection Watcher:{ZK HOSTS here} got event WatchedEvent
>> > state:Disconnected type:None path:null path:null type:None
>> >
>> > INFO  - 2016-04-21 12:37:57.536;
>> > org.apache.solr.common.cloud.ConnectionManager; zkClient has disconnected
>> >
>> > INFO  - 2016-04-21 12:38:24.248;
>> > org.apache.solr.common.cloud.DefaultConnectionStrategy; Connection
>> expired
>> > - starting a new one...
>> >
>> > INFO  - 2016-04-21 12:38:24.262;
>> > org.apache.solr.common.cloud.ConnectionManager; Waiting for client to
>> > connect to ZooKeeper
>> >
>> > INFO  - 2016-04-21 12:38:24.269;
>> > org.apache.solr.common.cloud.ConnectionManager; Connected:true
>> >
>> >
>> > Then it publishes all cores on the hosts are down.  I just list three
>> cores
>> > here:
>> >
>> > INFO  - 2016-04-21 12:38:24.269; org.apache.solr.cloud.ZkController;
>> > publishing core=product1_shard1_replica1 state=down
>> >
>> > INFO  - 2016-04-21 12:38:24.271; org.apache.solr.cloud.ZkController;
>> > publishing core=collection1 state=down
>> >
>> > INFO  - 2016-04-21 12:38:24.272; org.apache.solr.cloud.ZkController;
>> > numShards not found on descriptor - reading it from system property
>> >
>> > INFO  - 2016-04-21 12:38:24.289; org.apache.solr.cloud.ZkController;
>> > publishing core=product2_shard5_replica1 state=down
>> >
>> > INFO  - 2016-04-21 12:38:24.292; org.apache.solr.cloud.ZkController;
>> > publishing core=product2_shard13_replica1 state=down
>> >
>> >
>> > product1 has only one shard one replica and it's able to be active
>> > successfully:
>> >
>> > INFO  - 2016-04-21 12:38:26.383; org.apache.solr.cloud.ZkController;
>> > Register replica - core:product1_shard1_replica1 address:http://
>> > {internalIp}:8983/solr collection:product1 shard:shard1
>> >
>> > WARN  - 2016-04-21 12:38:26.385; org.apache.solr.cloud.ElectionContext;
>> > cancelElection did not find election node to remove
>> >
>> > INFO  - 2016-04-21 12:38:26.393;
>> > org.apache.solr.cloud.ShardLeaderElectionContext; Running the leader
>> > process for shard shard1
>> >
>> > INFO  - 2016-04-21 12:38:26.399;
>> > org.apache.solr.cloud.ShardLeaderElectionContext; Enough replicas found
>> to
>> > continue.
>> >
>> > INFO  - 2016-04-21 12:38:26.399;
>> > org.apache.solr.cloud.ShardLeaderElectionContext; I may be the new
>> leader -
>> > try and sync
>> >
>> > INFO  - 2016-04-21 12:38:26.399; org.apache.solr.cloud.SyncStrategy; Sync
>> > replicas to http://{internalIp}:8983/solr/product1_shard1_replica1/
>> >
>> > INFO  - 2016-04-21 12:38:26.399; org.apache.solr.cloud.SyncStrategy; Sync
>> > Success - now sync replicas to me
>> >
>> > INFO  - 2016-04-21 12:38:26.399; org.apache.solr.cloud.SyncStrategy;
>> > http://{internalIp}:8983/solr/product1_shard1_replica1/
>> > has no replicas
>> >
>> > INFO  - 2016-04-21 12:38:26.399;
>> > org.apache.solr.cloud.ShardLeaderElectionContext; I am the new leader:
>> > http://{internalIp}:8983/solr/product1_shard1_replica1/ shard1
>> >
>> > INFO  - 2016-04-21 12:38:26.399;
>> org.apache.solr.common.cloud.SolrZkClient;
>> > makePath: /collections/product1/leaders/shard1
>> >
>> > INFO  - 2016-04-21 12:38:26.412; org.apache.solr.cloud.ZkController; We
>> are
>> > http://{internalIp}:8983/solr/product1_shard1_replica1/ and leader is
>> > http://{internalIp}:8983/solr/product1_shard1_replica1/
>> >
>> > INFO  - 2016-04-21 12:38:26.412; org.apache.solr.cloud.ZkController; No
>> > LogReplay needed for core=product1_replica1 baseURL=http://
>> > {internalIp}:8983/solr
>> >
>> > INFO  - 2016-04-21 12:38:26.412; org.apache.solr.cloud.ZkController; I am
>> > the leader, no recovery necessary
>> >
>> > INFO  - 2016-04-21 12:38:26.413; org.apache.solr.cloud.ZkController;
>> > publishing core=product1_shard1_replica1 state=active
>> >
>> >
>> > product2 has 15 shards one replica but only two shards lived on this
>> > machine, this is one of the failed shard that I never seen the message of
>> > the core product2_shard5_replica1 active:
>> >
>> > INFO  - 2016-04-21 12:38:26.616; org.apache.solr.cloud.ZkController;
>> > Register replica - product2_shard5_replica1 address:http://
>> > {internalIp}:8983/solr collection:product2 shard:shard5
>> >
>> > WARN  - 2016-04-21 12:38:26.618; org.apache.solr.cloud.ElectionContext;
>> > cancelElection did not find election node to remove
>> >
>> > INFO  - 2016-04-21 12:38:26.625;
>> > org.apache.solr.cloud.ShardLeaderElectionContext; Running the leader
>> > process for shard shard5
>> >
>> > INFO  - 2016-04-21 12:38:26.631;
>> > org.apache.solr.cloud.ShardLeaderElectionContext; Enough replicas found
>> to
>> > continue.
>> >
>> > INFO  - 2016-04-21 12:38:26.631;
>> > org.apache.solr.cloud.ShardLeaderElectionContext; I may be the new
>> leader -
>> > try and sync
>> >
>> > INFO  - 2016-04-21 12:38:26.631; org.apache.solr.cloud.SyncStrategy; Sync
>> > replicas to http://
>> > {internalIp}:8983/solr/product2_shard5_replica1_shard5_replica1/
>> >
>> > INFO  - 2016-04-21 12:38:26.631; org.apache.solr.cloud.SyncStrategy; Sync
>> > Success - now sync replicas to me
>> >
>> > INFO  - 2016-04-21 12:38:26.632; org.apache.solr.cloud.SyncStrategy;
>> > http://{internalIp}:8983/solr/product2_shard5_replica1_shard5_replica1/
>> > has no replicas
>> >
>> > INFO  - 2016-04-21 12:38:26.632;
>> > org.apache.solr.cloud.ShardLeaderElectionContext; I am the new leader:
>> > http://{internalIp}:8983/solr/product2_shard5_replica1_shard5_replica1/
>> > shard5
>> >
>> > INFO  - 2016-04-21 12:38:26.632;
>> org.apache.solr.common.cloud.SolrZkClient;
>> > makePath: /collections/product2_shard5_replica1/leaders/shard5
>> >
>> > INFO  - 2016-04-21 12:38:26.645; org.apache.solr.cloud.ZkController; We
>> are
>> > http://{internalIp}:8983/solr/product2_shard5_replica1_shard5_replica1/
>> and
>> > leader is http://{internalIp}:8983/solr
>> > product2_shard5_replica1_shard5_replica1/
>> >
>> > INFO  - 2016-04-21 12:38:26.646;
>> > org.apache.solr.common.cloud.ZkStateReader; Updating cloud state from
>> > ZooKeeper...
>> >
>> >
>> > Before I restarted this server, a bunch of queries failed for this
>> > collection product2.  But I don't think it will affect the core status.
>> >
>> >
>> > Do you guys have any idea about why this particular core is not published
>> > as active since from the log, most steps are done except the very last
>> one
>> > to publish info to ZK.
>> >
>> >
>> > Thanks,
>> >
>> >
>> > Li
>> > On Thu, Apr 21, 2016 at 7:08 AM, Rajesh Hazari <rajeshhazari@gmail.com>
>> > wrote:
>> >
>> >> Hi Li,
>> >>
>> >> Do you see timeouts liek "CLUSTERSTATUS the collection time out:180s"
>> >> if its the case, this may be related to
>> >> https://issues.apache.org/jira/browse/SOLR-7940,
>> >> and i would say either use the patch file or upgrade.
>> >>
>> >>
>> >> *Thanks,*
>> >> *Rajesh,*
>> >> *8328789519,*
>> >> *If I don't answer your call please leave a voicemail with your contact
>> >> info, *
>> >> *will return your call ASAP.*
>> >>
>> >> On Thu, Apr 21, 2016 at 6:02 AM, YouPeng Yang <
>> yypvsxf19870706@gmail.com>
>> >> wrote:
>> >>
>> >> > Hi
>> >> >    We have used Solr4.6 for 2 years,If you post more logs ,maybe we
>> can
>> >> > fixed it.
>> >> >
>> >> > 2016-04-21 6:50 GMT+08:00 Li Ding <li.ding@bloomreach.com>:
>> >> >
>> >> > > Hi All,
>> >> > >
>> >> > > We are using SolrCloud 4.6.1.  We have observed following behaviors
>> >> > > recently.  A Solr node in a Solrcloud cluster is up but some of
the
>> >> cores
>> >> > > on the nodes are marked as down in Zookeeper.  If the cores are
>> parts
>> >> of
>> >> > a
>> >> > > multi-sharded collection with one replica,  the queries to that
>> >> > collection
>> >> > > will fail.  However, when this happened, if we issue queries to
the
>> >> core
>> >> > > directly, it returns 200 and correct info.  But once Solr got
into
>> the
>> >> > > state, the core will be marked down forever unless we do a restart
>> on
>> >> > Solr.
>> >> > >
>> >> > > Has anyone seen this behavior before?  Is there any to get out
of
>> the
>> >> > state
>> >> > > on its own?
>> >> > >
>> >> > > Thanks,
>> >> > >
>> >> > > Li
>> >> > >
>> >> >
>> >>
>>

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