Merge ~rharding/charm-telegraf:update-2.3 into ~telegraf-charmers/charm-telegraf:master

[Richard Harding]

Add support for using network-get in updated charm-helpers to fetch the correct IP address to send across the relation.

Per the new upcoming documentation here:
https://jujucharms.com/docs/devel/developer-network-primitives

This allows for using cross model relations from telegraf to a centralized prometheus instance and is meant to provide an example of charms to leverage network-get to help determine if a public or private address should be sent to a related application.

QA instructions:

CMR QA - Juju 2.3beta

You need two controllers
juju bootstrap google bigbrother
juju bootstrap aws monitorme
juju switch bigbrother
juju deploy cs:~rharding/prometheus-0
juju expose prometheus
juju offer prometheus:target offerprom
juju switch monitorme
juju deploy ubuntu
juju deploy cs:~rharding/telegraf-0
juju relate ubuntu:juju-info telegraf
juju consume bigbrother:/admin/default.offerprom promed
juju relate telegraf:prometheus-client promed:target
juju switch bigbrother
juju show-machine 0
<get the public IP of prometheus and load it in the browser <ip>:9090
<open the status->targets list and make sure you see the CMR with the public IP address of the telegraf unit in AWS>

[Haw Loeung (hloeung)]

LGTM, +1

review: Approve

diff --git a/reactive/telegraf.py b/reactive/telegraf.py
index 526ae97..b30bf17 100644
--- a/reactive/telegraf.py
+++ b/reactive/telegraf.py
@@ -648,41 +648,48 @@ def prometheus_client(prometheus):
 [[outputs.prometheus_client]]
   listen = "{{ listen }}"
 """
-    # if juju 2.x+ then we'll attempt to get the network space address
-    try:
-        ip_addr = hookenv.network_get_primary_address('prometheus-client')
-    except NotImplementedError:
-        # if that fails, just let prometheus.configure(...) do it's default
-        ip_addr = None
-    if get_prometheus_port():
-        hookenv.log("Prometheus configured globally, skipping plugin setup")
-        prometheus.configure(get_prometheus_port(),
+    for relation_id in hookenv.relation_ids('prometheus-client'):
+        # if juju 2.x+ then we'll attempt to get the network space address
+        try:
+            hookenv.log('Network Info')
+            network_info = hookenv.network_get('prometheus-client', relation_id=relation_id)
+            hookenv.log(network_info)
+            if 'ingress-addresses' in network_info:
+                ip_addr = network_info.get('ingress-addresses')[0]
+            else:
+                ip_addr = hookenv.network_get_primary_address('prometheus-client')
+        except NotImplementedError:
+            # if that fails, just let prometheus.configure(...) do it's default
+            ip_addr = None
+        if get_prometheus_port():
+            hookenv.log("Prometheus configured globally, skipping plugin setup")
+            prometheus.configure(get_prometheus_port(),
+                                 hostname=ip_addr,
+                                 private_address=ip_addr)
+            # bail out, nothing more need to be configured here
+            return
+        port = 9126
+        extra_options = get_extra_options()
+        options = extra_options['outputs'].get('prometheus-client', {})
+        listen = options.pop('listen', None)
+        if listen is not None:
+            hookenv.log("Configuring prometheus_client plugin to listen on: '{}'".format(listen))
+            port = int(listen.split(":", 1)[1])
+        else:
+            listen = ":{}".format(port)
+        check_prometheus_port("prometheus_output", port)
+        prometheus.configure(port,
                              hostname=ip_addr,
                              private_address=ip_addr)
-        # bail out, nothing more need to be configured here
-        return
-    port = 9126
-    extra_options = get_extra_options()
-    options = extra_options['outputs'].get('prometheus-client', {})
-    listen = options.pop('listen', None)
-    if listen is not None:
-        hookenv.log("Configuring prometheus_client plugin to listen on: '{}'".format(listen))
-        port = int(listen.split(":", 1)[1])
-    else:
-        listen = ":{}".format(port)
-    check_prometheus_port("prometheus_output", port)
-    prometheus.configure(port,
-                         hostname=ip_addr,
-                         private_address=ip_addr)
-    config_path = '{}/{}.conf'.format(get_configs_dir(), 'prometheus-client')
-    hookenv.log("Updating {} plugin config file".format('prometheus-client'))
-    context = {"listen": listen}
-    content = render_template(template, context) + \
-        render_extra_options("outputs", "prometheus_client",
-                             extra_options=extra_options)
-    host.write_file(config_path, content.encode('utf-8'))
-    set_state('plugins.prometheus-client.configured')
-    set_state('telegraf.needs_reload')
+        config_path = '{}/{}.conf'.format(get_configs_dir(), 'prometheus-client')
+        hookenv.log("Updating {} plugin config file".format('prometheus-client'))
+        context = {"listen": listen}
+        content = render_template(template, context) + \
+            render_extra_options("outputs", "prometheus_client",
+                                 extra_options=extra_options)
+        host.write_file(config_path, content.encode('utf-8'))
+        set_state('plugins.prometheus-client.configured')
+        set_state('telegraf.needs_reload')
 
 
 @when_not('prometheus-client.available')