Set the Primary Server

In mirror mode, when you are using the failover distribution method, the current child server that DAH sends actions to is the primary server. Similarly, in non-mirror mode, when you have child server groups set up to use the failover distribution method, the child server in each group that DAH sends actions to is the primary server.

By default, DAH selects the first child server listed in the configuration file (either the first [DistributedEngineN] section, or the first child server listed in the Host parameter for a server group). If this server stops responding, DAH switches to the next configured server, which becomes the primary server.

You can find the current primary server by sending an EngineManagement action. This action returns a <primary_engine> tag, which shows the ID of the current primary server. To find the primary server at any time, you can send the EngineManagement action with the EngineAction parameter set to ShowStatus.

When the first server comes online again,  DAH does not automatically switch back. If the server was offline for some time, it might not contain the latest data, so you might want to wait for the server to catch up with indexing jobs. At this point, you can manually change the primary server, by using the EngineManagement action, with the EngineAction parameter set to SetPrimaryEngine.


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