Configure a cluster member to run ad hoc searches only

A search head in a cluster typically services both ad hoc search requests from users and scheduled searches assigned by the captain. You can limit a cluster member to ad hoc search requests only. If you designate a member as an ad hoc search head, the captain will not assign it any scheduled searches.

You can designate an ad hoc search head in two ways:

• You can specify that a particular member run only ad hoc searches at all times.

• You can specify that a member run only ad hoc searches while it is the captain.

Note: Although you can specify that a member run only ad hoc searches, you cannot specify that it run only scheduled searches. Any cluster member can always run an ad hoc search. You can, of course, prevent user access to a search head through any number of means.

Configure a member to run ad hoc searches only

Depending on your specific deployment, you might want to reserve certain search heads for ad hoc use only. Ad hoc search heads will never run scheduled searches. To specify an ad hoc search head, set the adhoc_searchhead attribute in the member's server.conf file:

[shclustering]
adhoc_searchhead = true

You must restart the instance for the change to take effect.

Configure the captain to run ad hoc searches only

You can designate the captain member as an ad hoc search head. This prevents members from running scheduled searches while they are serving as captain, so that the captain can dedicate its resources to controlling the activities of the cluster. When the captain role moves to another member, then the previous captain will resume running scheduled searches and the new captain will now run ad hoc searches only.

Important: Make this change on all cluster members, so that the behavior is the same no matter which member is functioning as captain.

To designate the captain as an ad hoc search head, set the captain_is_adhoc_searchhead attribute in server.conf on each member:

[shclustering]
captain_is_adhoc_searchhead = true

You must restart each member for the change to take effect. Unlike most configuration changes related to search head clustering, you can use the splunk rolling-restart command to restart all members. See Restart the search head cluster.

For an overview of search head clustering configuration, see Configure the search head cluster.