Hi Hendrick - the shards in question have three replicas. I tried
restarting each one (one by one) - no luck. No leader is found. I
deleted one of the replicas and added a new one, and the new one also
shows as 'down'. I also tried the FORCELEADER call, but that had no
effect. I checked the OVERSEERSTATUS, but there is nothing unusual
there. I don't see anything useful in the logs except the error:
org.apache.solr.common.SolrException: Error getting leader from zk for
shard shard21
at org.apache.solr.cloud.ZkController.getLeader(ZkController.java:996)
at org.apache.solr.cloud.ZkController.register(ZkController.java:902)
at org.apache.solr.cloud.ZkController.register(ZkController.java:846)
at
org.apache.solr.core.ZkContainer.lambda$registerInZk$0(ZkContainer.java:181)
at
org.apache.solr.common.util.ExecutorUtil$MDCAwareThreadPoolExecutor.lambda$execute$0(ExecutorUtil.java:229)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by: org.apache.solr.common.SolrException: Could not get leader props
at
org.apache.solr.cloud.ZkController.getLeaderProps(ZkController.java:1043)
at
org.apache.solr.cloud.ZkController.getLeaderProps(ZkController.java:1007)
at org.apache.solr.cloud.ZkController.getLeader(ZkController.java:963)
... 7 more
Caused by: org.apache.zookeeper.KeeperException$NoNodeException:
KeeperErrorCode = NoNode for /collections/UNCLASS/leaders/shard21/leader
at
org.apache.zookeeper.KeeperException.create(KeeperException.java:111)
at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
at org.apache.zookeeper.ZooKeeper.getData(ZooKeeper.java:1151)
at
org.apache.solr.common.cloud.SolrZkClient$7.execute(SolrZkClient.java:357)
at
org.apache.solr.common.cloud.SolrZkClient$7.execute(SolrZkClient.java:354)
at
org.apache.solr.common.cloud.ZkCmdExecutor.retryOperation(ZkCmdExecutor.java:60)
at
org.apache.solr.common.cloud.SolrZkClient.getData(SolrZkClient.java:354)
at
org.apache.solr.cloud.ZkController.getLeaderProps(ZkController.java:1021)
... 9 more
Can I modify zookeeper to force a leader? Is there any other way to
recover from this? Thanks very much!
-Joe
On 11/21/2017 3:24 PM, Hendrik Haddorp wrote:
We sometimes also have replicas not recovering. If one replica is left
active the easiest is to then to delete the replica and create a new
one. When all replicas are down it helps most of the time to restart
one of the nodes that contains a replica in down state. If that also
doesn't get the replica to recover I would check the logs of the node
and also that of the overseer node. I have seen the same issue on Solr
using local storage. The main HDFS related issues we had so far was
those lock files and if you delete and recreate collections/cores and
it sometimes happens that the data was not cleaned up in HDFS and then
causes a conflict.
Hendrik
On 21.11.2017 21:07, Joe Obernberger wrote:
We've never run an index this size in anything but HDFS, so I have no
comparison. What we've been doing is keeping two main collections -
all data, and the last 30 days of data. Then we handle queries based
on date range. The 30 day index is significantly faster.
My main concern right now is that 6 of the 100 shards are not coming
back because of no leader. I've never seen this error before. Any
ideas? ClusterStatus shows all three replicas with state 'down'.
Thanks!
-joe
On 11/21/2017 2:35 PM, Hendrik Haddorp wrote:
We actually also have some performance issue with HDFS at the
moment. We are doing lots of soft commits for NRT search. Those seem
to be slower then with local storage. The investigation is however
not really far yet.
We have a setup with 2000 collections, with one shard each and a
replication factor of 2 or 3. When we restart nodes too fast that
causes problems with the overseer queue, which can lead to the queue
getting out of control and Solr pretty much dying. We are still on
Solr 6.3. 6.6 has some improvements and should handle these actions
faster. I would check what you see for
"/solr/admin/collections?action=OVERSEERSTATUS&wt=json". The
critical part is the "overseer_queue_size" value. If this goes up to
about 10000 it is pretty much game over on our setup. In that case
it seems to be best to stop all nodes, clear the queue in ZK and
then restart the nodes one by one with a gap of like 5min. That
normally recovers pretty well.
regards,
Hendrik
On 21.11.2017 20:12, Joe Obernberger wrote:
We set the hard commit time long because we were having performance
issues with HDFS, and thought that since the block size is 128M,
having a longer hard commit made sense. That was our hypothesis
anyway. Happy to switch it back and see what happens.
I don't know what caused the cluster to go into recovery in the
first place. We had a server die over the weekend, but it's just
one out of ~50. Every shard is 3x replicated (and 3x replicated in
HDFS...so 9 copies). It was at this point that we noticed lots of
network activity, and most of the shards in this recovery, fail,
retry loop. That is when we decided to shut it down resulting in
zombie lock files.
I tried using the FORCELEADER call, which completed, but doesn't
seem to have any effect on the shards that have no leader. Kinda
out of ideas for that problem. If I can get the cluster back up,
I'll try a lower hard commit time. Thanks again Erick!
-Joe
On 11/21/2017 2:00 PM, Erick Erickson wrote:
Frankly with HDFS I'm a bit out of my depth so listen to Hendrik
;)...
I need to back up a bit. Once nodes are in this state it's not
surprising that they need to be forcefully killed. I was more
thinking
about how they got in this situation in the first place. _Before_ you
get into the nasty state how are the Solr nodes shut down?
Forcefully?
Your hard commit is far longer than it needs to be, resulting in much
larger tlog files etc. I usually set this at 15-60 seconds with local
disks, not quite sure whether longer intervals are helpful on HDFS.
What this means is that you can spend up to 30 minutes when you
restart solr _replaying the tlogs_! If Solr is killed, it may not
have
had a chance to fsync the segments and may have to replay on startup.
If you have openSearcher set to false, the hard commit operation is
not horribly expensive, it just fsync's the current segments and
opens
new ones. It won't be a total cure, but I bet reducing this interval
would help a lot.
Also, if you stop indexing there's no need to wait 30 minutes if you
issue a manual commit, something like
.../collection/update?commit=true. Just reducing the hard commit
interval will make the wait between stopping indexing and restarting
shorter all by itself if you don't want to issue the manual commit.
Best,
Erick
On Tue, Nov 21, 2017 at 10:34 AM, Hendrik Haddorp
<hendrik.hadd...@gmx.net> wrote:
Hi,
the write.lock issue I see as well when Solr is not been stopped
gracefully.
The write.lock files are then left in the HDFS as they do not get
removed
automatically when the client disconnects like a ephemeral node in
ZooKeeper. Unfortunately Solr does also not realize that it
should be owning
the lock as it is marked in the state stored in ZooKeeper as the
owner and
is also not willing to retry, which is why you need to restart
the whole
Solr instance after the cleanup. I added some logic to my Solr
start up
script which scans the log files in HDFS and compares that with
the state in
ZooKeeper and then delete all lock files that belong to the node
that I'm
starting.
regards,
Hendrik
On 21.11.2017 14:07, Joe Obernberger wrote:
Hi All - we have a system with 45 physical boxes running solr
6.6.1 using
HDFS as the index. The current index size is about 31TBytes.
With 3x
replication that takes up 93TBytes of disk. Our main collection
is split
across 100 shards with 3 replicas each. The issue that we're
running into
is when restarting the solr6 cluster. The shards go into
recovery and start
to utilize nearly all of their network interfaces. If we start
too many of
the nodes at once, the shards will go into a recovery, fail, and
retry loop
and never come up. The errors are related to HDFS not
responding fast
enough and warnings from the DFSClient. If we stop a node when
this is
happening, the script will force a stop (180 second timeout) and
upon
restart, we have lock files (write.lock) inside of HDFS.
The process at this point is to start one node, find out the
lock files,
wait for it to come up completely (hours), stop it, delete the
write.lock
files, and restart. Usually this second restart is faster, but
it still can
take 20-60 minutes.
The smaller indexes recover much faster (less than 5 minutes).
Should we
have not used so many replicas with HDFS? Is there a better way
we should
have built the solr6 cluster?
Thank you for any insight!
-Joe
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