Enabling automatic failover
About this task
Follow these steps to enable automatic failover from the primary OpsCenter instance to the designated backup OpsCenter instance. Enabling failover requires minimal initial set up on the backup OpsCenter.
When configuring automatic failover, both the primary and secondary OpsCenter instances must be running the same OpsCenter version. The OpsCenter daemon (opscenterd) and the DataStax Agents must be running the same version before configuring high availability. DataStax cannot guarantee results if the primary and secondary OpsCenter instances are running different versions.
Ensure that address.yaml is not being managed by third-party Configuration Management.
During failover, OpsCenter automatically changes
Locate the opscenterd.conf and the address.yaml files.
The location of the opscenterd.conf file depends on the type of installation:
Package installations: /etc/opscenter/opscenterd.conf
Tarball installations: install_location/conf/opscenterd.conf
The location of the address.yaml file depends on the type of installation:
Package installations: /var/lib/datastax-agent/conf/address.yaml
Tarball installations: install_location/conf/address.yaml
Set up a hostname/IP that can switch between primary and backup OpsCenter instances to avoid changing the browser URL for OpsCenter if a failover occurs. If you do not set up a hostname or IP for seamless URL switching post-failover, inform your OpsCenter users of any alternate URL to access OpsCenter.
To override the primary OpsCenter URL generated by OpsCenter during failover, set the override_primary_redirect_url option in opscenterd.conf.
Mirror the configuration directories stored on the primary OpsCenter instance to the backup OpsCenter instance using the method you prefer, such as NFS mount or rysnc. See Backing up critical configuration data for instructions on backing up the active OpsCenter instance to the standby instance.
Create and run an automated script to keep the mirrored directories in sync. The following example cron scripts run rsync to synchronize the configuration directories every 5 minutes.
*/5 * * * * /usr/bin/rsync -az /etc/opscenter <user>@<backup_host>:/etc/opscenter
*/5 * * * * /usr/bin/rsync -az /var/lib/opscenter/ssl <user>@<backup_host>:/var/lib/opscenter/ssl
*/5 * * * * /usr/bin/rsync -az install_location/conf <user>@<backup_host>:install_location/conf
*/5 * * * * /usr/bin/rsync -az install_location/ssl <user>@<backup_host>:install_location/ssl
When a failover occurs, you must manually stop the sync scripts on the former primary OpsCenter instance and start the sync scripts on the new primary OpsCenter instance. Failure to do so will result in configuration changes on the new primary OpsCenter instance being overwritten by stale files from the former primary OpsCenter instance.
If you want to override the default values, edit the failover section of the OpsCenter configuration file opscenterd.conf.
Making any changes to the opscenterd.conf file requires restarting OpsCenter.
Table 1. OpsCenter daemon failover default configuration parameters Option Description Default
Frequency (in seconds) with which the primary OpsCenter instance sends a heartbeat to the backup OpsCenter instance.
Frequency (in seconds) with which the OpsCenter backup instance sends a heartbeat to the primary OpsCenter instance.
Amount of time (in seconds) that must elapse before the lack of a heartbeat triggers a failover.
Directory location where failover-specific configuration is stored. The
failover_idfile is also located in the failover directory.
Do not mirror the failover_configuration_directory across OpsCenter installs when configuring OpsCenter to support failover.
/var/lib/opscenter/failover/ (package installs)
install_location/failover/ (tarball installs)
If set, overrides the primary OpsCenter URL automatically generated during failover. Example:
https://opscenter:80. This option provides more flexibility for setting a port in the redirect URL.
Empty. Allows OpsCenter to generate the redirect URL for the newly primary OpsCenter instance switched from backup OpsCenter instance status.
On the backup OpsCenter instance, in the failover directory, create a
primary_opscenter_locationconfiguration file that indicates the IP address of the primary OpsCenter daemon to monitor:
primary_opscenter_location file should only contain the IP address of the primary OpsCenter instance and nothing more:
Ensure the user running OpsCenter has at least read permission for the
Before the backup OpsCenter instance can take over as the primary OpsCenter instance, the backup OpsCenter instance deletes the
primary_opscenter_location file in the event of a failover.
After a failover, recreate the
primary_opscenter_location file on the newly designated backup OpsCenter instance.