Merge ~hloeung/charm-nrpe:master into ~nrpe-charmers/charm-nrpe:master

[Haw Loeung]

Use the correct IP address in exported host cfgs

Work around LP: #1736050 and use socket connect to work out the
correct IP address for the exported host cfgs.

[Paul Collins (pjdc)]

see inline

review: Needs Fixing

[Paul Collins (pjdc)]

review: Approve (lgtm)

[Paul Gear (paulgear)]

I think it would be good to move the socket connect code into charmhelpers so that it can be used from multiple charms. This seems like something we'll likely have to do again.

[Haw Loeung (hloeung)]

At present, the code tries to connect to what's configured as the "nagios_master", I'm not sure what would we use in charmhelpers. Feel free to open a bug/wishlist against charmhelpers though.

[Paul Gear (paulgear)]

The protocol, host, and port would be parameters to the method:

def get_outbound_address(host='ntp.ubuntu.com', port=123, proto=socket.SOCK_DGRAM):
    s = socket.socket(socket.AF_INET, proto)
    s.connect(host, port)
    address = s.getsockname()[0]
    s.close()
    return address

diff --git a/hooks/nrpe_helpers.py b/hooks/nrpe_helpers.py
index cfcb348..32ee7b6 100644
--- a/hooks/nrpe_helpers.py
+++ b/hooks/nrpe_helpers.py
@@ -1,7 +1,7 @@
 import glob
 import socket
-import yaml
 import subprocess
+import yaml
 
 from charmhelpers.core.services import helpers
 from charmhelpers.core import hookenv
@@ -205,8 +205,24 @@ class NagiosInfo(dict):
                 "{},{}".format(self['external_nagios_master'],
                                hookenv.config('nagios_master'))
         self['nagios_hostname'] = self.principal_relation.nagios_hostname()
-        ip_key = hookenv.config('nagios_address_type') + '-address'
-        self['nagios_ipaddress'] = hookenv.unit_get(ip_key)
+
+        address = None
+        if hookenv.config('nagios_address_type').lower() == 'public':
+            address = hookenv.unit_get('public-address')
+        elif hookenv.config('nagios_master') != 'None':
+            # Try to work out the correct interface/IP. We can't use both
+            # network-get nor 'unit-get private-address' because both can
+            # return the wrong IP on systems with more than one interface
+            # (LP: #1736050).
+            s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+            s.connect((hookenv.config('nagios_master'), 80))
+            address = s.getsockname()[0]
+            s.close()
+        # Fallback to unit-get private-address
+        if not address:
+            address = hookenv.unit_get('private-address')
+
+        self['nagios_ipaddress'] = address
 
         self['dont_blame_nrpe'] = '1' if hookenv.config('dont_blame_nrpe') else '0'
         self['debug'] = '1' if hookenv.config('debug') else '0'