Merge ~aluria/charm-telegraf:remote-unit-name into ~telegraf-charmers/charm-telegraf:master

[Alvaro Uria]

[James Hebden (ec0)]

The reason for added the code you are removing was that when deployed to units which have multiple networks, we had observed the returned private address may not be routable between the telegraf unit and the prometheus server is was related to as a target. The below code fixed that by being sympathetic to the primary network address of the space the relation was bound to, rather than using the units private IP address.

This is the 4th case which we also need to test against - when the prometheus target relation is bound to a different space in order to gain access to a server only accessible on a network other than the unit's detected private address - for example when deployed alongside a Ceph monitor where the storage access network may be picked up for the private-address.

review: Needs Information

[Alvaro Uria (aluria)]

I understand this kind of check you mention is needed to send telegraf unit hostname (the target) to its relation (ie. prometheus) -- but this MP only affects which unit_name telegraf is related to (and each telegraf unit can only be related to a single unit, so I think there's no need of further IP matching verifications).

The issue I hit can be seen at https://pastebin.canonical.com/208764/

The IP verification to set telegraf's "hostname" key is managed in another part of the code:
https://git.launchpad.net/telegraf-charm/tree/reactive/telegraf.py#n652

[Peter Sabaini (peter-sabaini)]

+1 after Alvaros' persuasive argument :-)

review: Approve

diff --git a/reactive/telegraf.py b/reactive/telegraf.py
index 7521b97..f8d0b27 100644
--- a/reactive/telegraf.py
+++ b/reactive/telegraf.py
@@ -111,15 +111,7 @@ def get_remote_unit_name():
         rels = hookenv.relations_of_type(rel_type)
         if rels and len(rels) >= 1:
             rel = rels[0]
-            try:
-                ip_addr = hookenv.network_get_primary_address('prometheus-client')
-            except NotImplementedError:
-                ip_addr = hookenv.unit_private_ip()
-            if rel['private-address'] == ip_addr:
-                return rel['__unit__']
-
-            if rel['private-address'] == hookenv.unit_private_ip():
-                return rel['__unit__']
+            return rel['__unit__']
 
 
 def render_base_inputs():