Zookeeper connection error

Question

We have a standalone zookeeper setup on a dev machine  It works fine for every other dev machine except this one testdev machine   We get this error over and over again when trying to connect to zookeeper through testdev   2012-11-09 14 06 53 909 - INFO   main-SendThread zk01 dev bunchball net 2181  ClientCnxn SendThread 947  - Socket connection established to zk01 dev bunchball net 192 168 8 58 2181  initiating session 2012-11-09 14 06 53 911 - INFO   main-SendThread zk01 dev bunchball net 2181  ClientCnxn SendThread 1183  - Unable to read additional data from server sessionid 0x0  likely server has closed socket  closing socket connection and attempting reconnect 2012-11-09 14 06 55 366 - INFO   main-SendThread zk01 dev bunchball net 2181  ClientCnxn SendThread 1058  - Opening socket connection to server zk01 dev bunchball net 192 168 8 58 2181 2012-11-09 14 06 55 368 - INFO   main-SendThread zk01 dev bunchball net 2181  ClientCnxn SendThread 947  - Socket connection established to zk01 dev bunchball net 192 168 8 58 2181  initiating session 2012-11-09 14 06 55 368 - INFO   main-SendThread zk01 dev bunchball net 2181  ClientCnxn SendThread 1183  - Unable to read additional data from server sessionid 0x0  likely server has closed socket  closing socket connection and attempting reconnect 2012-11-09 14 06 57 271 - INFO   main-SendThread zk01 dev bunchball net 2181  ClientCnxn SendThread 1058  - Opening socket connection to server zk01 dev bunchball net 192 168 8 58 2181 2012-11-09 14 06 57 274 - INFO   main-SendThread zk01 dev bunchball net 2181  ClientCnxn SendThread 947  - Socket connection established to zk01 dev bunchball net 192 168 8 58 2181  initiating session 2012-11-09 14 06 57 275 - INFO   main-SendThread zk01 dev bunchball net 2181  ClientCnxn SendThread 1183  - Unable to read additional data from server sessionid 0x0  likely server has closed socket  closing socket connection and attempting reconnect   We tried restarting the test dev machine  and also restart zookeeper host but nothing worked  We are totally confused why it works perfectly fine with other machines except this one  What might be the cause of this

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Check the zookeeper logs   var log zookeeper   It looks like a connection is established  which should mean there is a record of it   I had the same situation and it was because a process opened connections and failed to close them  This eventually exceeded the per-host connection limit and my logs were overflowing with  2016-08-03 15 21 13 201  myid   - WARN   NIOServerCxn Factory 0 0 0 0 0 0 0 0 2181 NIOServerCnxnFactory 188  - Too many connections from  172 31 38 64 - max is 50   Assuming zookeeper is on the usual port  you could do a check for that with   lsof -i -P   grep 2181

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Just now I solved the same question and post a blog   In brief  if xx s zoo cfg like   server 1 xx 2888 3888 server 2 yy 2888 3888 server 3 zz 2888 3888   then xx s myid 1 is must

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I also ran into this problem last week and have managed to fix this now  I got the idea to resolve this one from the response shared by  gukoff   My requirement and situation was slightly different from the ones shared so far but the issue was fundamentally the same so I thought of sharing it on this thread    I was actually trying to query zookeeper quorum  after every 30 seconds  for some information from my application and was using the Curator Framework for this purpose  the methods available in LeaderLatch class   So  essentially I was starting up a CuratorFramework client and supplying this to LeaderLatch object   Only after I ran into the error mentioned in this thread - I realised that I did not close the zookeeper client connection s  established in my applications  The maxClientCnxns property had the value of 60 and as soon as the number of connections  all of them were stale connections  touched 60  my application started complaining with this error    I found out about the number of open connections by     Checking the zookeeper logs  where there were warning messages stating  Too many connections from  IP address of the host   Running the following netstat command from the same host mentioned in the above logs where my application was running       netstat -no   grep  2181   wc -l   Note  The 2181 port is the default for zookeeper supplied as a parameter in grep to match the zookeeper connections   To fix this  I cleared up all of those stale connections manually and then added the code for closing the zookeeper client connections gracefully in my application   I hope this helps

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This can happen if there are too many open connections   Try increasing the maxClientCnxns setting   From documentation      maxClientCnxns    No Java system property       Limits the number of concurrent connections  at the socket level  that a single client  identified by IP address  may make to a single member of the ZooKeeper ensemble  This is used to prevent certain classes of DoS attacks  including file descriptor exhaustion  Setting this to 0 or omitting it entirely removes the limit on concurrent connections    You can edit settings in the config file  Most likely it can be found at  etc zookeeper conf zoo cfg    In modern ZooKeeper versions default value is 60  You can increase it by adding the maxClientCnxns 4096 line to the end of the config file

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Unable to read additional data from server sessionid 0x0  likely server has closed socket  closing socket connection and attempting reconnect  org apache zookeeper ClientCnxn   I changed just the number of brokers in the zoo cfg file and  restart  zookeeper and kafka service

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Make sure all required services are running  Step 1   Check if hbase-master is running   sudo  etc init d hbase-master status   if not  then start it sudo  etc init d hbase-master start  Step 2   Check if hbase-regionserver is running   sudo  etc init d hbase-regionserver status   if not  then start it sudo  etc init d hbase-regionserver start  Step 3   Check if zookeeper-server is running   sudo  etc init d zookeeper-server status   if not  then start it sudo  etc init d zookeeper-server start    or simply run these 3 commands in a row   sudo  etc init d hbase-master restart sudo  etc init d hbase-regionserver restart sudo  etc init d zookeeper-server restart   after that don t forget to check the status   sudo  etc init d hbase-master status sudo  etc init d hbase-regionserver status sudo  etc init d zookeeper-server status   You might find that zookeeper is still not running  then you can run the zookeeper  sudo  usr lib zookeeper bin zkServer sh stop sudo  usr lib zookeeper bin zkServer sh start   after that again check the status and make sure its running  sudo  etc init d zookeeper-server status   This should work

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I was able to start with zookeeper and kafka having 2 nodes each  I got the error because i had started zookeeper with   zkServer sh instead of the kafka wrapper bin zookeeper-server-start sh config zookeeper properties

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leave only one entry for your host IP in  etc hosts file  it resolved

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I just have the same situation as you and I have just fixed this problem   It is the reason that you have configured even number of zookeepers which directly result in  this problem try to change your number of zookeeper node to a odd one   for example the original status of my zookeeper cluster is consisted of 4 nodes then just remove one of them which result in the number of node to be 3 well  now its ok to startup zookeeper cluster  below is the output of successfully connect to zookeeper server  2013-04-22 22 07 05 654  myid   - INFO   main ZooKeeper 438  - Initiating client connection  connectString localhost 2181 sessionTimeout 30000 watcher org apache zookeeper ZooKeeperMain MyWatcher 1321ed6 Welcome to ZooKeeper  2013-04-22 22 07 05 704  myid   - INFO   main-SendThread localhost 2181  ClientCnxn SendThread 966  - Opening socket connection to server localhost 127 0 0 1 2181  Will not attempt to authenticate using SASL  unknown error  JLine support is enabled 2013-04-22 22 07 05 727  myid   - INFO   main-SendThread localhost 2181  ClientCnxn SendThread 849  - Socket connection established to localhost 127 0 0 1 2181  initiating session  zk  localhost 2181 CONNECTING  0  2013-04-22 22 07 05 846  myid   - INFO   main-SendThread localhost 2181  ClientCnxn SendThread 1207  - Session establishment complete on server localhost 127 0 0 1 2181  sessionid   0x13e3211c06e0000  negotiated timeout   30000

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I have just solved the problem  I am using centos 7  And the trouble-maker is firewall Using  systemctl stop firewalld  to shut it all down in each server can simply solve the problem Or you can use command like   firewall-cmd --zone public --add-port 2181 udp --add-port 2181 tcp --permanent  to configure all three ports  include 2181 2888 3888 in each server And then  firewall-cmd --reload   Finally use   zkServer sh restart   to restart your servers and problem solved

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I was having the same error when I was trying to connect my broker with my Zookeeper ensemble using A records to point to Zookeeper IPs  The problem was in my zookeepers  My zookeepers were not able to bind to port 2181 because I was pointing my A records to public IP  This was preventing the zookeeper ensemble to choose a leader and communicate with each other  Pointing A records to private IP enabled the zookeeper ensemble to choose a leader and the cluster became active  After this when I tried to  connect one of my brokers to the ensemble  it connected successfully

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I had this problem too  and it turned out that I was telling zookeeper to connect to the wrong port  Have you verified that zookeeper is actually running on port 2181 on the dev machine

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I had this problem too  and I found that I just need to restart zookeeper  then restart tomcat so my webapp connected nicely then

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This is a common issue if the Zookeeper server is not running or no longer running  i e  it crashed after you started it      So first  check that you have the Zookeeper server running   A simple way to check is grep the running processes     ps -ef   grep zookeeper    run this a couple of times to see if the same process ID is still there    its possible it keep restarting with a new process ID   Alternatively you can use  systemctl status zookeeper  if your Linux distro support systemd   You should see the process running as a java process     ps -ef   grep zookeeper root       492     0  0 00 01 pts 1    00 00 00 java -Dzookeeper log dir   -Dzookeeper root logger INFO CONSOLE -cp  root zookeeper-3 5 0-alpha bin    build classes  root zookeeper-3 5 0-alpha bin    build lib   jar  root zookeeper-3 5 0-alpha bin    lib slf4j-log4j12-1 7 5 jar  root zookeeper-3 5 0-alpha bin    lib slf4j-api-1 7 5 jar  root zookeeper-3 5 0-alpha bin    lib servlet-api-2 5-20081211 jar  root zookeeper-3 5 0-alpha bin    lib netty-3 7 0 Final jar  root zookeeper-3 5 0-alpha bin    lib log4j-1 2 16 jar  root zookeeper-3 5 0-alpha bin    lib jline-2 11 jar  root zookeeper-3 5 0-alpha bin    lib jetty-util-6 1 26 jar  root zookeeper-3 5 0-alpha bin    lib jetty-6 1 26 jar  root zookeeper-3 5 0-alpha bin    lib javacc jar  root zookeeper-3 5 0-alpha bin    lib jackson-mapper-asl-1 9 11 jar  root zookeeper-3 5 0-alpha bin    lib jackson-core-asl-1 9 11 jar  root zookeeper-3 5 0-alpha bin    lib commons-cli-1 2 jar  root zookeeper-3 5 0-alpha bin    zookeeper-3 5 0-alpha jar  root zookeeper-3 5 0-alpha bin    src java lib   jar  root zookeeper-3 5 0-alpha bin    conf  -Xmx1000m -Xmx1000m -Dcom sun management jmxremote -Dcom sun management jmxremote local only false org apache zookeeper server quorum QuorumPeerMain  root zookeeper-3 5 0-alpha bin    conf zoo cfg   If its not there  then there s likely something in the zookeeper log file indicating the issue     To find the zookeeper log file  you should first figure out where its configured for logging   In my case I have zookeeper installed under my root directory  not suggesting you install it there     root centos6 zookeeper conf   pwd  root zookeeper-3 5 0-alpha conf   And you can find the log setting in this file    root centos6 zookeeper conf   grep  zookeeper log  log4j properties  zookeeper log dir  var log zookeeper log file zookeeper log zookeeper log threshold INFO zookeeper log maxfilesize 256MB zookeeper log maxbackupindex 20   So Zookeeper is configured to log under  var log   Then there s usually a zookeeper log and or zookeeper out file which should indicate your startup error

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I encountered same problem  too  In my case the problem is about iptables rules   To communicate with zookeeper node  2181 port must be accept incoming request  also for internal communication between zookeeper nodes 2888 3888 ports must be open for incoming request   iptables -t nat -I PREROUTING -p tcp -s 10 0 0 0 24 --dport 2181 -j DNAT --to-destination serverIp 2181 iptables -t nat -I PREROUTING -p udp -s 10 0 0 0 24 --dport 2181 -j DNAT --to-destination serverIp 2181  iptables -t nat -I PREROUTING -p tcp -s 10 0 0 0 24 --dport 2888 -j DNAT --to-destination serverIp 2888 iptables -t nat -I PREROUTING -p udp -s 10 0 0 0 24 --dport 2888 -j DNAT --to-destination serverIp 2888  iptables -t nat -I PREROUTING -p tcp -s 10 0 0 0 24 --dport 3888 -j DNAT --to-destination serverIp 3888 iptables -t nat -I PREROUTING -p udp -s 10 0 0 0 24 --dport 3888 -j DNAT --to-destination serverIp 3888  sudo service iptables save

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I just have the same situation as you and I have just fixed this problem   my conf zoo cfg just like this   server 1 10 194 236 32 2888 3888 server 2 10 194 236 33 2888 3888 server 3 10 208 177 15 2888 3888 server 4 10 210 154 23 2888 3888 server 5 10 210 154 22 2888 3888   then i set data myid file content like this   1        at host  10 194 236 32 2        at host  10 194 236 33 3        at host  10 208 177 15 4        at host  10 210 154 23 5        at host  10 210 154 22   finally restart zookeeper

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In my case  I config zoo cfg like this   server 1 host-1 2888 3888 server 2 host-2 2888 3888 server 3 host-3 2888 3888   But  in host-1  I config host-1 resolve to 127 0 0 1 in  etc hosts   127 0 0 1   localhost host-1   which may results other hosts can t communicate with it  Resolve host-1 to its real ip solved this problem   Hope this can help

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I also get the same error when i started my replicated zk  one of zkClient can not connect to localhost 2181  i checked the log file under apache-zookeeper-3 5 5-bin logs directory  and found this      2019-08-20 11 30 39 763  myid 5  - WARN     QuorumPeermyid 5 secure disabled  QuorumCnxManager 677    - Cannot open channel to 3 at election address  xxxx 3888 java net SocketTimeoutException  connect timed out  at   java net PlainSocketImpl socketConnect Native Method      at   java net AbstractPlainSocketImpl doConnect AbstractPlainSocketImpl java 350      at   java net AbstractPlainSocketImpl connectToAddress AbstractPlainSocketImpl java 206      at   java net AbstractPlainSocketImpl connect AbstractPlainSocketImpl java 188      at java net SocksSocketImpl connect SocksSocketImpl java 392    at   java net Socket connect Socket java 589   at   org apache zookeeper server quorum QuorumCnxManager connectOne QuorumCnxManager java 648      at   org apache zookeeper server quorum QuorumCnxManager connectOne QuorumCnxManager java 705      at   org apache zookeeper server quorum QuorumCnxManager connectAll QuorumCnxManager java 733      at   org apache zookeeper server quorum FastLeaderElection lookForLeader FastLeaderElection java 910      at   org apache zookeeper server quorum QuorumPeer run QuorumPeer java 1247    2019-08-20 11 30 44 768  myid 5  - WARN     QuorumPeermyid 5 secure disabled  QuorumCnxManager 677    - Cannot open channel to 4 at election address  xxxxxx 3888 java net SocketTimeoutException  connect timed out    at   java net PlainSocketImpl socketConnect Native Method      at   java net AbstractPlainSocketImpl doConnect AbstractPlainSocketImpl java 350      at   java net AbstractPlainSocketImpl connectToAddress AbstractPlainSocketImpl java 206      at   java net AbstractPlainSocketImpl connect AbstractPlainSocketImpl java 188      at java net SocksSocketImpl connect SocksSocketImpl java 392    at   java net Socket connect Socket java 589   at   org apache zookeeper server quorum QuorumCnxManager connectOne QuorumCnxManager java 648      at   org apache zookeeper server quorum QuorumCnxManager connectOne QuorumCnxManager java 705      at   org apache zookeeper server quorum QuorumCnxManager connectAll QuorumCnxManager java 733      at   org apache zookeeper server quorum FastLeaderElection lookForLeader FastLeaderElection java 910      at   org apache zookeeper server quorum QuorumPeer run QuorumPeer java 1247    2019-08-20 11 30 44 769  myid 5  - INFO     QuorumPeermyid 5 secure disabled  FastLeaderElection 919    - Notification time out  51200   that means this zk server can not connect to other servers  and i found this server ping other servers fail  and after remove this server from the replica  the problem is solved   hope this will be helpful

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I faced the same issue and found it was due to zookeeper cluster nodes needs ports opened to communicate with each other   server 1 xx xx xx xx 2888 3888  server 2 xx xx xx xx 2888 3888  server 3 xx xx xx xx 2888 3888   once i allowed these ports through aws security group and restarted  All worked fine for me

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This can happen despite the ZooKeeper servers being up and running and the socket open and accepting connections  if one or more of the ZooKeeper disks are out of space  This can easily happen if the old ZK snapshot and log files are never cleaned up      The ZooKeeper server creates snapshot and log files  but never deletes them  The retention policy of the data and log files is implemented outside of the ZooKeeper server  The server itself only needs the latest complete fuzzy snapshot  all log files following it  and the last log file preceding it  The latter requirement is necessary to include updates which happened after this snapshot was started but went into the existing log file at that time  This is possible because snapshotting and rolling over of logs proceed somewhat independently in ZooKeeper  See the maintenance section in this document for more details on setting a retention policy and maintenance of ZooKeeper storage    There is a maintenance job that can be run to clean up old snapshot and log files  See https   zookeeper apache org doc r3 4 12 zookeeperAdmin html sc maintenance

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I start standalone instance in my machine  and encounter the same problem  Finally  I change from ip  127 0 0 1  to  localhost  and the problem is gone

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Had the same error during setup on a 2 node cluster  I discovered I had mixed up the contents of the myid file versus the server id HOST IP port entry   Essentially  if you have two servers  SERVER1 and SERVER2  for which you have created  myid  files in dataDir for zookeeper as below   SERVER1  myid  1  SERVER2  myid  2   Ensure the entry in your zoo cfg file corresponds for each of these i e server 1 should use SERVER1 hostname and server 2 should use SERVER2 hostname followed by the port as below  SERVER1  zoo cfg       other config omitted  server 1 SERVER1 2888 3888 server 2 SERVER2 2888 3888  SERVER2  zoo cfg       other config omitted  server 1 SERVER1 2888 3888 server 2 SERVER2 2888 3888   Just to make sure  I also deleted the version-  folder in the dataDir then restarted Zookeeper to get it working

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Also check the local firewall  service firewalld status  If it s running  just stop it service firewalld stop  And then give it a try

[apache-zookeeper] Zookeeper connection error

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