Installing Cloudera Manager with High Availability

Steps to install Cloudera Manager with high availability.

  1. Provision an external database for use by Cloudera Manager.
  2. Provision two hosts for Cloudera Manager.
  3. Repeat the steps to install Cloudera Manager on each of the hosts to be used for Cloudera Manager high availability. Skip these auto-TLS steps on the passive host. Do not start Cloudera Manager on any hosts until you complete the following:

    1. Configure both the active and passive Cloudera Manager instances to connect to the same database. You configure this by running the scm_prepare_database.sh script on each Cloudera Manager host. Specify the database host with the --host option.

      1. On each Cloudera Manager host, edit the following file: /etc/default/cloudera-scm-server

      2. Find the line that begins with export CMF_JAVA_OPTS and add the following parameter:
        -Dcom.cloudera.cmf.haMode=true
      3. Find the line that begins with export CMF_SERVER_ARGS and insert the following inside the quotes: --ha-priority <number>

      The --ha-priority sets the priority of the server. The number has to be a non zero positive integer. The lower the number is, the higher priority the server has. Thus, the active server should have a smaller “ha-priority” number than the passive server. When the hardware of the previous running host gets replaced, make sure the new active server always has a higher priority (smaller ha-priority number) than the passive server. To start with, the suggested values are ‘10’ for the active server, and ‘20’ for the passive server. Increment by 10 for each additional passive server.

      For example:
      export CMF_SERVER_ARGS=”--ha-priority 10”
      export CMF_JAVA_OPTS="-Xmx2G -XX:MaxPermSize=256m -XX:+HeapDumpOnOutOfMemoryError  -XX:HeapDumpPath=/tmp -Dcom.cloudera.cmf.haMode=t
    2. Save the file

  4. Start one instance of Cloudera Manager and wait for the Cloudera Manager server to come online.

  5. Start the Load Balancer.

  6. Configure the Cloudera Manager Hostname Override:

    1. Log in to the Cloudera Manager Admin Console, and go to Administration > Settings.

    2. Select Ports and Addresses.

    3. Set the Cloudera Manager Hostname Override parameter to contain the fully qualified domain name of the load balancer.

  7. If you have enabled TLS for Cloudera Manager, do the following:

    1. Locate the Verify Agent Hostname Against Certificate configuration parameter, and uncheck it. (Go to Administration > Settings and search for this parameter.)
    2. Ensure that the CA certificate signing the load balancer’s TLS certificate is trusted by Cloudera Manager server.
    3. The CA certificate signing the load balancer’s TLS certificate must be specified in the file referenced by the Cloudera Manager TLS/SSL Client Trust Store File configuration parameter (Go to Administration > Settings and search for this parameter.)
  8. Restart the active instance of Cloudera Manager Server.
  9. CM agents on all hosts must point to load balancer for communicating with CM servers.
    If you are adding high availability to an existing set of hosts managed by Cloudera Manager, configure the Cloudera Manager agents on all managed hosts with the fully-qualified domain name of the load balancer.

    If your host provisioning system automatically adds new hosts to Cloudera Manager without using the Cloudera Manager Add Host wizard, ensure the above server_host line in the /etc/cloudera-scm-agent/config.ini is configured with the fully-qualified domain name of the load balancer. This may be needed in systems using pre-created host images.

  10. If you have enabled TLS for Cloudera Manager, the CA certificate signing the load balancer’s TLS certificate must be specified. On all Cloudera Manager-managed hosts, add the following to the /etc/cloudera-scm-agent/config.ini file:
    verify_cert_file=load_balancer_ca_cert.pem

    (Replace load_balancer_ca_cert.pem with the file containing the certificate.)

  11. Perform rotation of Auto-TLS certificates (See Rotate Auto-TLS Certificate Authority and Host Certificates) with location parameter set to blank to store the certificates in DB instead of file system. This is important to ensure that both the hosts are able to use the auto TLS certificates after rotation.
  12. Restart the Cloudera Manager agents by running the following command on all managed hosts:
    sudo service cloudera-scm-agent restart
  13. Start the passive instance of the Cloudera Manager server.
  14. Continue with cluster installation and wait for the new cluster to start up.
  15. Verify that both Cloudera Manager hosts are showing good health in the Cloudera Manager Admin Console. (Go to Hosts > All Hosts to check the status of the hosts of the Cloudera Manager Servers.)

Replacing Cloudera Manager Hosts

Primary/secondary node fails:
  1. Set up a new Cloudera Manager server node as per above steps
  2. Update the load balancer configuration to update the host name of replaced host.
  3. Ensure that the priority of active host remains higher (smaller value of the --ha-priority property) than the passive host.
  4. Ensure the Cloudera Manager server is running on the host before restarting load balancer.
  5. Restart load balancer server.
Load Balancer fails
  1. Set up a new load balancer using the existing configuration.
  2. Ensure that the load balancer endpoint remains the same as it is configured in the Cloudera Manager server and agents.