About Host Tag Constraints

All default templates allow you to limit on which hosts a given database TE and SM process can be started. Without specifying host tag constraints, any host in the domain will be a candidate to start an SM or TE. Each host (broker) in the domain can be tagged with a set of key/value pairs. When creating a database from a template, you can optionally specify a host tag constraint — in the following example, the enforcer will query the domain to find a host tagged with "Storefront" and create SM process(es) only on such hosts.

The template language provides the following tag constraint functions:

All constraints other than ex: and nx: have a parameter. The parameter should follow the colon (:) delimiter. For example, eq:val means the host must have the specified key with value val.

Some examples for host tag constraints: