Repository Failover
In a Tableau Server installation, the repository (pgsql) database is one of the key required processes. The Tableau Server repository stores information about Tableau Server users, groups and group assignments, permissions, projects, data sources, and extract metadata and refresh information. Because it is critical to the server functioning, Tableau Server has a built-in automatic "failover" for the repository when server is installed in a distributed environment that meets certain requirements.
Automatic repository failover
Automatic repository failover means that if there is a problem with the active Tableau Server repository, the server will automatically switch to using the passive repository. This does not happen immediately, to protect against ephemeral issues with the repository that don't justify a switch, but if the repository is unavailable for more than 1-5 minutes, failover occurs. For example, if the underlying PostgresSQL service fails, then failover will occur in about a minute. However other configuration problems may not trigger a failure for up to 5 minutes.
For automatic repository failover to work, your Tableau Server installation needs:
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A minimum of three nodes
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Two instances of the repository installed
Optional but highly recommended:
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A multi-node Coordination Service ensemble deployed
With these conditions satisfied, repository failover will occur if the active repository becomes unavailable, either due to a problem with the process, or a problem with the node the process is running on. If the original repository becomes available again (if, for example, the node is restarted and all processes come up properly), it is made the passive repository, available for failover if necessary.
Manual repository failover
There may be reasons you want to shift back to the original repository after failover occurs. One reason would be if that instance of the repository is installed on a computer with more resources. To do this, use the tsm topology failover-repository command to manually switch back to the original repository. For more information, see tsm topology failover-repository.
Preferred active repository
When you configure Tableau Server you have the option to specify a node as the preferred active repository. When Tableau Server is configured for repository failover, the preferred active repository node is the one used for the active repository. This is an optional step, and if you do not specify a preferred active repository node, Tableau Server will select the active repository node on startup.
To configure the preferred active repository, use the tsm configuration set command to configure the pgsql.preferred_host option:
tsm configuration set -k pgsql.preferred_host -v "<host_name>"
Note: The host_name is case-sensitive and must match the node name shown in the output of tsm status -v.
Configure a preferred active repository node if you want Tableau Server to select a specific node on startup. You might want to do this if you have a particular server you want to use for your active repository (a computer with more disk space or memory for example), or if you are using custom administrative views. Custom administrative views have embedded connection information that refers to the repository for which you created the views. For more information on connecting to the Tableau Server repository, see Collect Data with the Tableau Server Repository