Zookeeper error: Cannot open channel to X at election address

I have installed zookeeper in 3 different aws servers. The following is the configuration in all the servers

tickTime=2000
initLimit=10
syncLimit=5
dataDir=/var/zookeeper
clientPort=2181
server.1=x.x.x.x:2888:3888
server.2=x.x.x.x:2888:3888
server.3=x.x.x.x:2888:3888

All the three instance have a myid file at var/zookeeper with appropriate id in it. All the three servers have all ports open from the aws console. But when I run the zookeeper server, I get the following error in all the instances.

2015-06-19 12:09:22,989 [myid:1] - WARN  [QuorumPeer[myid=1]/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@382] 
  - Cannot open channel to 2 at election address /x.x.x.x:3888
java.net.ConnectException: Connection refused
  at java.net.PlainSocketImpl.socketConnect(Native Method)
  at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
  at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
  at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
  at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
  at java.net.Socket.connect(Socket.java:579)
  at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:368)
  at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:402)
  at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:840)
  at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:762)
2015-06-19 12:09:23,170 [myid:1] - WARN  [QuorumPeer[myid=1]/0:0:0:0:0:0:0:0:2181:QuorumCnxManager@382]
   - Cannot open channel to 3 at election address /x.x.x.x:3888
java.net.ConnectException: Connection refused
  at java.net.PlainSocketImpl.socketConnect(Native Method)
  at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
  at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
  at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
  at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
  at java.net.Socket.connect(Socket.java:579)
  at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:368)
  at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectAll(QuorumCnxManager.java:402)
  at org.apache.zookeeper.server.quorum.FastLeaderElection.lookForLeader(FastLeaderElection.java:840)
  at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:762)
2015-06-19 12:09:23,170 [myid:1] - INFO  [QuorumPeer[myid=1]/0:0:0:0:0:0:0:0:2181:FastLeaderElection@849] - Notification time out: 25600

How have defined the ip of the local server in each node? If you have given the public ip, then the listener would have failed to connect to the port. You must specify 0.0.0.0 for the current node

server.1=0.0.0.0:2888:3888
server.2=192.168.10.10:2888:3888
server.3=192.168.2.1:2888:3888

This change must be performed at the other nodes too.

I met the save question and solved it.

make sure the myid is the save with your configuration in the zoo.cfg.

please check your zoo.cfg file in your conf directory, which contains such content.

server.1=zookeeper1:2888:3888  
server.2=zookeeper2:2888:3888  
server.3=zookeeper3:2888:3888  

and check the myid in your server dataDir directory. For example:

let's say the dataDir defined on the zoo.cfg is '/home/admin/data'

then on zookeeper1, you must have a file named myid and have value 1 on this file ;on zookeeper2, you must have a file named myid and have value 2 on this file; on zookeeper3, you must have a file named myid and have value 3 on this file.

if not configured like this, the server will listen on a wrong ip:port.

Here is some ansible jinja2 template info for automating the build of a cluster with the 0.0.0.0 hostname in zoo.cfg

{% for url in zookeeper_hosts_list %}
  {%- set url_host = url.split(':')[0] -%}
  {%- if url_host == ansible_fqdn or url_host in     ansible_all_ipv4_addresses -%}
server.{{loop.index0}}=0.0.0.0:2888:3888
{% else %}
server.{{loop.index0}}={{url_host}}:2888:3888
{% endif %}
{% endfor %}

If your own hostname resolves to 127.0.0.1 (In my case, the hostname was in /etc/hosts), zookeeper won't start up without having 0.0.0.0 in the zoo.cfg file, but if your hostname resolves to the actual machine's IP, you can put it's own hostname in the config file.

This is what worked for me

Step 1:
Node 1:
zoo.cfg
server.1= 0.0.0.0:<port>:<port2>
server.2= <IP>:<port>:<port2>
.
.
.
server.n= <IP>:<port>:<port2>

Node 2 :
server.1= <IP>:<port>:<port2>
server.2= 0.0.0.0:<port>:<port2>
.
.
.
server.n= <IP>:<port>:<port2>


Now in location defined by datadir on your zoo.cfg
Node 1:
echo 1 > <datadir>/id

Node 2:
echo 2 > <datadir>/id

.
.
.


Node n:
echo n > <datadir>/id

This one helped me to start zoo keeper successfully but will know more once i start playing with it. Hope this helps.

Had similar issues on a 3-Node zookeeper ensemble. Solution was as advised by espeirasbora and restarted.

So this was what I did

zookeeper1,zookeeper2 and zookeeper3

A. Issue :: znodes in my ensemble could not start

B. System SetUp :: 3 Znodes in three 3 machines

C. Error::

In my zookeper log file I could see the following errors

2016-06-26 14:10:17,484 [myid:1] - WARN  [SyncThread:1:FileTxnLog@334] - fsync-ing the write ahead log in SyncThread:1 took 1340ms which will adversely effect operation latency. See the ZooKeeper troubleshooting guide
2016-06-26 14:10:17,847 [myid:1] - WARN  [RecvWorker:2:QuorumCnxManager$RecvWorker@810] - Connection broken for id 2, my id = 1, error = 
java.io.EOFException
	at java.io.DataInputStream.readInt(DataInputStream.java:392)
	at org.apache.zookeeper.server.quorum.QuorumCnxManager$RecvWorker.run(QuorumCnxManager.java:795)
2016-06-26 14:10:17,848 [myid:1] - WARN  [RecvWorker:2:QuorumCnxManager$RecvWorker@813] - Interrupting SendWorker
2016-06-26 14:10:17,849 [myid:1] - WARN  [SendWorker:2:QuorumCnxManager$SendWorker@727] - Interrupted while waiting for message on queue
java.lang.InterruptedException
	at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.reportInterruptAfterWait(AbstractQueuedSynchronizer.java:2014)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2088)
	at java.util.concurrent.ArrayBlockingQueue.poll(ArrayBlockingQueue.java:418)
	at org.apache.zookeeper.server.quorum.QuorumCnxManager.pollSendQueue(QuorumCnxManager.java:879)
	at org.apache.zookeeper.server.quorum.QuorumCnxManager.access$500(QuorumCnxManager.java:65)
	at org.apache.zookeeper.server.quorum.QuorumCnxManager$SendWorker.run(QuorumCnxManager.java:715)
2016-06-26 14:10:17,851 [myid:1] - WARN  [SendWorker:2:QuorumCnxManager$SendWorker@736] - Send worker leaving thread
2016-06-26 14:10:17,852 [myid:1] - WARN  [QuorumPeer[myid=1]/0:0:0:0:0:0:0:0:2181:Follower@89] - Exception when following the leader
java.io.EOFException
	at java.io.DataInputStream.readInt(DataInputStream.java:392)
	at org.apache.jute.BinaryInputArchive.readInt(BinaryInputArchive.java:63)
	at org.apache.zookeeper.server.quorum.QuorumPacket.deserialize(QuorumPacket.java:83)
	at org.apache.jute.BinaryInputArchive.readRecord(BinaryInputArchive.java:99)
	at org.apache.zookeeper.server.quorum.Learner.readPacket(Learner.java:153)
	at org.apache.zookeeper.server.quorum.Follower.followLeader(Follower.java:85)
	at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:846)
2016-06-26 14:10:17,854 [myid:1] - INFO  [QuorumPeer[myid=1]/0:0:0:0:0:0:0:0:2181:Follower@166] - shutdown called
java.lang.Exception: shutdown Follower

D. Actions & Resolution ::

On each znode a. I modified the configuration file $ZOOKEEPER_HOME/conf/zoo.cfg to set the machines IP to "0.0.0.0" while maintaining the IP addressof the other 2 znodes. b. restarted the znode c. checked the status d.Voila , I was ok

See below

-------------------------------------------------##

on Zookeeper1

#Before modification 
[zookeeper1]$ tail -3   $ZOOKEEPER_HOME/conf/zoo.cfg 
server.1=zookeeper1:2888:3888
server.2=zookeeper2:2888:3888
server.3=zookeeper3:2888:3888

#After  modification 
[zookeeper1]$ tail -3  $ZOOKEEPER_HOME/conf/zoo.cfg 
server.1=0.0.0.0:2888:3888
server.2=zookeeper2:2888:3888
server.3=zookeeper3:2888:3888

#Start the Zookeper (Stop and STart or restart )
[zookeeper1]$ $ZOOKEEPER_HOME/bin/zkServer.sh  start
ZooKeeper JMX enabled by default
ZooKeeper remote JMX Port set to 52128
ZooKeeper remote JMX authenticate set to false
ZooKeeper remote JMX ssl set to false
ZooKeeper remote JMX log4j set to true
Using config: /opt/zookeeper-3.4.8/bin/../conf/zoo.cfg
Mode: follower

[zookeeper1]$ $ZOOKEEPER_HOME/bin/zkServer.sh  status
ZooKeeper JMX enabled by default
ZooKeeper remote JMX Port set to 52128
ZooKeeper remote JMX authenticate set to false
ZooKeeper remote JMX ssl set to false
ZooKeeper remote JMX log4j set to true
Using config: /opt/zookeeper-3.4.8/bin/../conf/zoo.cfg
Mode: follower

---------------------------------------------------------##

on Zookeeper2

#Before modification 
[zookeeper2]$ tail -3   $ZOOKEEPER_HOME/conf/zoo.cfg 
server.1=zookeeper1:2888:3888
server.2=zookeeper2:2888:3888
server.3=zookeeper3:2888:3888

#After  modification 
[zookeeper2]$ tail -3  $ZOOKEEPER_HOME/conf/zoo.cfg 
server.1=zookeeper1:2888:3888
server.2=0.0.0.0:2888:3888
server.3=zookeeper3:2888:3888

#Start the Zookeper (Stop and STart or restart )
[zookeeper2]$ $ZOOKEEPER_HOME/bin/zkServer.sh  start
ZooKeeper JMX enabled by default
ZooKeeper remote JMX Port set to 52128
ZooKeeper remote JMX authenticate set to false
ZooKeeper remote JMX ssl set to false
ZooKeeper remote JMX log4j set to true
Using config: /opt/zookeeper-3.4.8/bin/../conf/zoo.cfg
Mode: follower

[zookeeper2]$ $ZOOKEEPER_HOME/bin/zkServer.sh  status
ZooKeeper JMX enabled by default
ZooKeeper remote JMX Port set to 52128
ZooKeeper remote JMX authenticate set to false
ZooKeeper remote JMX ssl set to false
ZooKeeper remote JMX log4j set to true
Using config: /opt/zookeeper-3.4.8/bin/../conf/zoo.cfg
Mode: follower

---------------------------------------------------------##

on Zookeeper3

#Before modification 
[zookeeper3]$ tail -3   $ZOOKEEPER_HOME/conf/zoo.cfg 
server.1=zookeeper1:2888:3888
server.2=zookeeper2:2888:3888
server.3=zookeeper3:2888:3888

#After  modification 
[zookeeper3]$ tail -3  $ZOOKEEPER_HOME/conf/zoo.cfg 
server.1=zookeeper1:2888:3888
server.2=zookeeper2:2888:3888
server.3=0.0.0.0:2888:3888

#Start the Zookeper (Stop and STart or restart )
[zookeeper3]$ $ZOOKEEPER_HOME/bin/zkServer.sh  start
ZooKeeper JMX enabled by default
ZooKeeper remote JMX Port set to 52128
ZooKeeper remote JMX authenticate set to false
ZooKeeper remote JMX ssl set to false
ZooKeeper remote JMX log4j set to true
Using config: /opt/zookeeper-3.4.8/bin/../conf/zoo.cfg
Mode: follower

[zookeeper3]$ $ZOOKEEPER_HOME/bin/zkServer.sh  status
ZooKeeper JMX enabled by default
ZooKeeper remote JMX Port set to 52128
ZooKeeper remote JMX authenticate set to false
ZooKeeper remote JMX ssl set to false
ZooKeeper remote JMX log4j set to true
Using config: /opt/zookeeper-3.4.8/bin/../conf/zoo.cfg
Mode: follower

In mycase, the issue was, I had to start all the three zookeeper servers, Only then I was able to connect to zookeeper server using ./zkCli.sh

Adding additional info regarding Zookeeper clustering inside Amazon's VPC. Solution with '0.0.0.0' is working in case of Zookeeper running directly inside EC2 instance, in case when you are using docker '0.0.0.0' will not work properly with Zookeeper 3.5.X after node restart.

The issue lies in resolving '0.0.0.0' and ensemble sharing of node addresses and SID order (if you will start your nodes in descending order, this issue may not occur).

So far the only working solution is to upgrade to 3.6.2+ version.

We faced the same issue , for our case the root cause of the problem is too-many number of client connections . The default ulimit on aws ec2 instance is 1024 and this causes zookeeper nodes not able to communicate with each other .

The fix for this is change the ulimit to a higher number -> (> ulimit -n 20000 ) stop and start zookeeper.

I had a similar issue. The status on 2 of my three zookeeper nodes was listed as "standalone", even though the zoo.cfg file indicated that it should be clustered. My third node couldn't start, with the error you described. I think what fixed it for me was running zkServer.sh start in quick succession across my three nodes, such that zookeeper was running before the zoo.cfg initLimit was reached. Hope this works for someone out there.

I had the same error log, in my case, i use hostname of my node in zookeeper.conf.

My nodes were on virtual machine in Centos 8.

Like @user2286693 said, my mistake was the resolution mechanism:

Since node1, when I ping node1:

PING node1(localhost (::1)) 56 data bytes

I check my /etc/hosts file and I find:

127.0.0.1   localhost localhost.localdomain localhost4 
localhost4.localdomain4 node1

I replace this line by:

127.0.0.1   localhost localhost.localdomain localhost4 
localhost4.localdomain4

and it's working!

Hope this help someone!

When you are having this issue, you will see something like this:

org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss
  at org.apache.zookeeper.KeeperException.create(KeeperException.java:99) ~[zookeeper-3.4.6.jar:3.4.6-1569965]

This indicates a network communication issue with Zookeeper is the cause.

How to fix it

Scale down zk to 0. Then scale back up to 3. Wait for them to all show ready.

Now go to zk-0 oc rsh zk-0 and run this command:

/opt/fusion/bin/zookeeper-client
Connecting to zk-0.zk:9983,zk-1.zk:9983,zk-2.zk:9983

(--- paused for a moment here ---)

Welcome to ZooKeeper!
JLine support is enabled

[zk: zk-0.zk:9983,zk-1.zk:9983,zk-2.zk:9983(CONNECTING) 0] 

Notice how it still says "CONNECTING". This means you did not get a successful communication with zookeeper.

You will see this in the /opt/fusion/var/log/zookeeper/zookeeper.log when this happens:

2021-04-17T00:45:52,848 - WARN  [WorkerSender[myid=1]:QuorumCnxManager@584] - Cannot open channel to 2 at election address zk-2.zk:3888
java.net.UnknownHostException: zk-2.zk
        at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184) ~[?:1.8.0_262]
        at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[?:1.8.0_262]
        at java.net.Socket.connect(Socket.java:607) ~[?:1.8.0_262]
        at org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:558) [zookeeper-3.4.13.jar:3.4.13-2d71af4dbe22557fda74f9a9b4309b15a7487f03]
        at org.apache.zookeeper.server.quorum.QuorumCnxManager.toSend(QuorumCnxManager.java:534) [zookeeper-3.4.13.jar:3.4.13-2d71af4dbe22557fda74f9a9b4309b15a7487f03]
        at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.process(FastLeaderElection.java:454) [zookeeper-3.4.13.jar:3.4.13-2d71af4dbe22557fda74f9a9b4309b15a7487f03]
        at org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.run(FastLeaderElection.java:435) [zookeeper-3.4.13.jar:3.4.13-2d71af4dbe22557fda74f9a9b4309b15a7487f03]
        at java.lang.Thread.run(Thread.java:748) [?:1.8.0_262]

This is actually the infamous "No route to host exception" that we get on our OpenShift pods once and a while. When this is happening, zookeeper will show Ready but it is not able to communicate with the other zookeepers, so it's actually not ready in a sense.

How to fix this then?

Scale zk statefulset to 0, then back up to 3 again.

And repeat until you get a successful connection:

/opt/fusion/bin/zookeeper-client
Connecting to zk-0.zk:9983,zk-1.zk:9983,zk-2.zk:9983
Welcome to ZooKeeper!
JLine support is enabled

WATCHER::

WatchedEvent state:SyncConnected type:None path:null
[zk: zk-0.zk:9983,zk-1.zk:9983,zk-2.zk:9983(CONNECTED) 0]

Notice the CONNECTED

Now you can restart the rest of your services that depend on zk.

I got the same because the quorum server port 3181 was still used by another service - changing the port fixed it