Hi Kevin -
* HDFS is part of Cloudera 5.12.0.
* Solr is co-located in most cases. We do have several nodes that run
on servers that are not data nodes, but most do. Unfortunately, our
nodes are not the same size. Some nodes have 8TBytes of disk, while our
largest nodes are 64TBytes. This results in a lot of data that needs to
go over the network.
* Command is:
/usr/lib/jvm/jre-1.8.0/bin/java -server -Xms12g -Xmx16g -Xss2m
-XX:+UseG1GC -XX:MaxDirectMemorySize=11g -XX:+PerfDisableSharedMem
-XX:+ParallelRefProcEnabled -XX:G1HeapRegionSize=16m
-XX:MaxGCPauseMillis=300 -XX:InitiatingHeapOccupancyPercent=75
-XX:+UseLargePages -XX:ParallelGCThreads=16 -XX:-ResizePLAB
-XX:+AggressiveOpts -verbose:gc -XX:+PrintHeapAtGC -XX:+PrintGCDetails
-XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps
-XX:+PrintTenuringDistribution -XX:+PrintGCApplicationStoppedTime
-Xloggc:/opt/solr6/server/logs/solr_gc.log -XX:+UseGCLogFileRotation
-XX:NumberOfGCLogFiles=9 -XX:GCLogFileSize=20M -DzkClientTimeout=300000
-DzkHost=frodo.querymasters.com:2181,bilbo.querymasters.com:2181,gandalf.querymasters.com:2181,cordelia.querymasters.com:2181,cressida.querymasters.com:2181/solr6.6.0
-Dsolr.log.dir=/opt/solr6/server/logs -Djetty.port=9100 -DSTOP.PORT=8100
-DSTOP.KEY=solrrocks -Dhost=tarvos -Duser.timezone=UTC
-Djetty.home=/opt/solr6/server -Dsolr.solr.home=/opt/solr6/server/solr
-Dsolr.install.dir=/opt/solr6 -Dsolr.clustering.enabled=true
-Dsolr.lock.type=hdfs -Dsolr.autoSoftCommit.maxTime=120000
-Dsolr.autoCommit.maxTime=1800000 -Dsolr.solr.home=/etc/solr6
-Djava.library.path=/opt/cloudera/parcels/CDH/lib/hadoop/lib/native
-Xss256k -Dsolr.log.muteconsole
-XX:OnOutOfMemoryError=/opt/solr6/bin/oom_solr.sh 9100
/opt/solr6/server/logs -jar start.jar --module=http
* We have enabled short circuit reads.
Right now, we have a relatively small block cache due to the
requirements that the servers run other software. We tried to find the
best balance between block cache size, and RAM for programs, while still
giving enough for local FS cache. This came out to be 84 128M blocks -
or about 10G for the cache per node (45 nodes total).
<directoryFactory name="DirectoryFactory"
class="solr.HdfsDirectoryFactory">
<bool name="solr.hdfs.blockcache.enabled">true</bool>
<bool name="solr.hdfs.blockcache.global">true</bool>
<int name="solr.hdfs.blockcache.slab.count">84</int>
<bool
name="solr.hdfs.blockcache.direct.memory.allocation">true</bool>
<int name="solr.hdfs.blockcache.blocksperbank">16384</int>
<bool name="solr.hdfs.blockcache.read.enabled">true</bool>
<bool name="solr.hdfs.nrtcachingdirectory.enable">true</bool>
<int name="solr.hdfs.nrtcachingdirectory.maxmergesizemb">128</int>
<int name="solr.hdfs.nrtcachingdirectory.maxcachedmb">1024</int>
<str name="solr.hdfs.home">hdfs://nameservice1:8020/solr6.6.0</str>
<str name="solr.hdfs.confdir">/etc/hadoop/conf.cloudera.hdfs1</str>
</directoryFactory>
Thanks for reviewing!
-Joe
On 11/22/2017 8:20 AM, Kevin Risden wrote:
Joe,
I have a few questions about your Solr and HDFS setup that could help
improve the recovery performance.
* Is HDFS part of a distribution from Hortonworks, Cloudera, etc?
* Is Solr colocated with HDFS data nodes?
* What is the output of "ps aux | grep solr"? (specifically looking for the
Java arguments that are being set.)
Depending on how Solr on HDFS was setup, there are some potentially simple
settings that can help significantly improve performance.
1) Short circuit reads
If Solr is colocated with an HDFS datanode, short circuit reads can improve
read performance since it skips a network hop if the data is local to that
node. This requires HDFS native libraries to be added to Solr.
2) HDFS block cache in Solr
Solr without HDFS uses the OS page cache to handle caching data for
queries. With HDFS, Solr has a special HDFS block cache which allows for
caching HDFS blocks. This significantly helps query performance. There are
a few configuration parameters that can help here.
Kevin Risden
On Wed, Nov 22, 2017 at 4:20 AM, Hendrik Haddorp <hendrik.hadd...@gmx.net>
wrote:
Hi Joe,
sorry, I have not seen that problem. I would normally not delete a replica
if the shard is down but only if there is an active shard. Without an
active leader the replica should not be able to recover. I also just had a
case where all replicas of a shard stayed in down state and restarts didn't
help. This was however also caused by lock files. Once I cleaned them up
and restarted all Solr instances that had a replica they recovered.
For the lock files I discovered that the index is not always in the
"index" folder but can also be in an index.<timestamp> folder. There can be
an "index.properties" file in the "data" directory in HDFS and this
contains the correct index folder name.
If you are really desperate you could also delete all but one replica so
that the leader election is quite trivial. But this does of course increase
the risk of finally loosing the data quite a bit. So I would try looking
into the code and figure out what the problem is here and maybe compare the
state in HDFS and ZK with a shard that works.
regards,
Hendrik
On 21.11.2017 23:57, Joe Obernberger wrote:
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$0(
ZkContainer.java:181)
at org.apache.solr.common.util.ExecutorUtil$MDCAwareThreadPoolE
xecutor.lambda$execute$0(ExecutorUtil.java:229)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPool
Executor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoo
lExecutor.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(ZkControll
er.java:1043)
at org.apache.solr.cloud.ZkController.getLeaderProps(ZkControll
er.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(SolrZkCl
ient.java:357)
at org.apache.solr.common.cloud.SolrZkClient$7.execute(SolrZkCl
ient.java:354)
at org.apache.solr.common.cloud.ZkCmdExecutor.retryOperation(Zk
CmdExecutor.java:60)
at org.apache.solr.common.cloud.SolrZkClient.getData(SolrZkClie
nt.java:354)
at org.apache.solr.cloud.ZkController.getLeaderProps(ZkControll
er.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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