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This is useful when the user needs to have hosts in the same scheduler (like with dependencies) but needs some hosts or services checks to be checked by specific pollers (see usage cases below).
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The parameter to tag a command, host or service, is "poller_tag". If a check uses a "tagged" or "untagged" command in a untagged host/servicecheck, it takes the poller_tag of this host/servicecheck. In a "untagged" host/servicecheck, it's the command tag that is taken into consideration.
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