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[Contrail] Troubleshooting the Apache ZooKeeper process

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Article ID: KB30906 KB Last Updated: 13 Jul 2016Version: 1.0
Summary:

Contrail uses the Apache ZooKeeper process to maintain synchronization of Contrail configuration, analytics and database running on the different instances of controllers. This article provides a list of helpful points related to Contrail and the Apache ZooKeeper process that can be used for troubleshooting.

Symptoms:

 Provide troubleshooting tips on the Apache ZooKeeper process for Contrail users.

Cause:
 
Solution:
ZooKeeper helps in :
  1. Election: Services like service monitor, device monitor, contrail schema are active-backup. ZooKeeper helps in election of active service. Apart from these three services, all other Contrail services are active-active.
  2. Locking: ZooKeeper locks resources to avoid data inconsistency.
  3. Allocation of resources: ZooKeeper helps allocate resources like IP addresses. In case of concurrent requests from multiple services for same resource, it makes sure the resources are uniquely utilized.

Helpful points:

  • Ports 2888 and 3888 are the default ports. This info is stored in /etc/zookeeper/conf/zoo.cfg. The configuration should be consistent across all controller nodes. Make sure the process is listening on that port on all controller nodes:

    #netstat –lnp | grep 2181
  • Each controller instance gets a unique ZooKeeper ID stored in /etc/zookeeper/conf/myid. Make sure it is unique on every controller.

  • Only one controller instance is in leader mode. All others are in follower mode. To check which controller is in what mode, run the following commands on the controller CLI:

    Telnet to port 2180 to connect to ZooKeeper:

    root@ccpe-8:~# telnet localhost 2181 
    Trying ::1...
    Connected to localhost.
    Escape character is '^]'.

    When the connection is established, enter the command "stat":

    stat                                    
    ZooKeeper version: 3.4.5--1, built on 06/10/2013 17:26 GMT
    Clients:
    /10.85.29.9:38238[1](queued=0,recved=570834,sent=570834)
    /10.85.29.9:38248[1](queued=0,recved=570846,sent=570846)
    /0:0:0:0:0:0:0:1:48017[0](queued=0,recved=1,sent=0)

    Latency min/avg/max: 0/0/3
    Received: 1141692
    Sent: 1141691
    Connections: 3
    Outstanding: 0
    Zxid: 0x600000062
    Mode: leader
    Node count: 341
    Connection closed by foreign host.
    root@ccpe-8:~#

  • ZooKeeper also depends on Java. Current versions of Contrail (2.X and 3.0) support JDK version1.7.0_79.

    #java -version
    java version "1.7.0_79"
    OpenJDK Runtime Environment (IcedTea 2.5.6) (7u79-2.5.6-0ubuntu1.14.04.1)
    OpenJDK 64-Bit Server VM (build 24.79-b02, mixed mode)
  • ZooKeeper logs: ZooKeeper server logs are located at /var/log/ZooKeeper/ZooKeeper.log on the controller nodes. The Contrail API process uses ZooKeeper; the logs are located at /var/log/contrail/api-0-zk.log on the controller node.

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