Description
Currently, you have at the time of template writing whether or not you're binding to a service that is in a topology (e.g. leader) or not. when writing your template, you either choose something like this for finding the leader:
{{~ #if bind.database}}
{{~ #eachAlive bind.database.members as |member|}}
{{~ #if member.leader}}
PGHOST="{{member.sys.ip}}"
{{~ /if}}
{{~ /eachAlive}}
{{~ /if}}
but if the service isn't in a topology, member.leader will always be false and instead users are instructed to rely on the @first or @last helpers. There's no way to detect if a given service is in a topology or not, so you have to know this in advance and that makes reuse difficult.
Ideally, I would want to do something like this in my template:
{{~#if bind.database}}
{{~#if bind.database.topology?}}
{{~#findLeader bind.database.members as |member|}}
PGHOST="{{member.sys.ip}}"
{{~/findLeader}}
{{else}}
# loop through via #eachAlive
{{~/if}}
{{~/if}}
or an even more terse way would be something like:
{{~#if bind.database.topology?}}
PGHOST={{bind.database.leader.sys.ip}}
{{else}}
{{~/if}}
pie in the sky, but a "just do the right thing" pointer that would choose the leader the in a leader topology or any alive member at random in a non-leader topology would be the nicest from a user perspective