Resource tags are metaparameters available to all resources in Puppet. They are used in collecting only and do not affect the definition of resources.

Any tags explicitly set on a resource will be appended to the array of tags. In our previous example, we saw the tags for our host entry in the PostgreSQL output as follows, but we didn't address what the tags meant:

{server,ldap,host,class,ldap::server,default,node,ldap-ldapserver1}

All these tags are defaults set by Puppet. To illustrate how tags are used, we can create multiple exported host entries with different tags. We'll start with adding a tag search to our Host collector in the base class as follows:

Host <<| tag == 'ldap-server' |>>

Then we'll add an ldap-client exported host resource to the base class with the tag 'ldap-client' as follows:

@@host {"ldap-client-$::hostname":
  host_aliases => ["$::fqdn","another-$::hostname"],
  ip           => "$::ipaddress",
  tag         => 'ldap-client',
}

Now all nodes will only collect Host resources marked as ldap-server. Every node will create an ldap-client exported host resource; we'll add a collector for those to the ldap::server class:

Host <<| tag == 'ldap-client' |>>

One last change: we need to make our ldap-server resource-specific, so we'll add a tag to it in ldap::server as follows:

@@host {"ldap-$::hostname":
  host_aliases => ["$::fqdn",'ldap'],
  ip           => "$::ipaddress",
  tag          => 'ldap-server',
}

Now every node with the ldap::server class exports a host resource tagged with ldap-server and collects all host resources tagged with ldap-client. After running Puppet on master and client nodes 1 and 2, we see the following on our ldapserver1 as the host resources tagged with ldap-client get defined: