How to get the ip addresses of all units in a service in a charm-hook in another service?

Question

I am new to Juju and trying to write a charm. I need ip address of all units deployed in a service. I am currently using juju 1.25 And deploying services in openstack

The scenario is:

I have 3 units of wordpress(it has required relation hook files) with

juju deploy -n 3 cs:wordpress

I deployed my charm from local repo

juju deploy local:trusty/myCharm

I add relation between the two

juju add-relation myCharm wordpress

Now, I need list of all 3 ip addresses of wordpress service in one of the hook in myCharm

I set relation-keys in wordpress and tried using relation-ids -> relation-list -> relation-get hook tools in myCharm. But it gives me just one ip and not all three.

relation-ids {relationName}  --gives one id. 
relation-list -r {id} --gives just one unit(wordpress/18). 
relation-get -r {id} {relation-key} {unit} --gives corresponding ip.

What should I do to get expected result?

Answer 1

The relation-list -r {id} should return all units in the relation. Perhaps you're only parsing the first (or last) value?

This is what my relation-* output looks like when I have multiple units of one application related to another (in this case, i'm looking at the monitors relation data between nagios and 3 units of nrpe; you probably want to substitute those with myCharm and your 3 units of wordpress):

$ juju run --unit nagios/0 'relation-ids monitors'
monitors:1

$ juju run --unit nagios/0 'relation-list -r monitors:1'  
nrpe/0
nrpe/1
nrpe/2

$ juju run --unit nagios/0 'relation-get -r monitors:1 private-address nrpe/0'
172.31.13.216

I can put that all together in a loop that outputs the private-address for all units related to nagios like this:

$ juju run --unit nagios/0 'for i in `relation-ids monitors`; do for j in `relation-list -r $i`; do relation-get -r $i private-address $j; done; done'
172.31.13.216
172.31.30.157
172.31.49.121