Changing/renewing a certificate generally requires restarting or
reloading some service. Since the *cert* role is intended to be generic
and reusable, it naturally does not know what action to take to effect
the change. It works well for the initial deployment of a new
application, since the service is reloaded anyway in order for the new
configuration to be applied. It fails, however, for continuous
enforcement, when a certificate is renewed automatically (i.e. by
`lego`) but no other changes are being made. This has caused a number
of disruptions when some certificate expires and its replacement is
available but has not yet been loaded.
To address this issue, I have added a handler "topic" notification to
the *certs* role. When either the certificate or private key file is
replaced, the relevant task will "notify" a generic handler "topic."
This allows some other role to define a specific handler, which
"listens" for these notifications, and takes the appropriate action for
its respective service.
For this mechanism to work, though, the *cert* role can only be used as
a dependency of another role. That role must define the handler and
configure it to listen to the generic "certificate changed" topic. As
such, each of the roles that are associated with a certificate deployed
by the *cert* role now declare it as a dependency, and the top-level
playbooks only include those roles.
Dustin
d1cdc8bfc3