add juju availability zone to ceph osd location when present

The approach here is to use the availability zone as an imaginary rack.
All hosts that are in the same AZ will be in the same imaginary rack.
From Ceph's perspective this doesn't matter as it's just a bucket after all.
This will give users the ability to further customize their ceph deployment.

Change-Id: Ie25ac1b001db558d6a40fe3eaca014e8f4174241

hooks/ceph_hooks.py

@@ -12,6 +12,7 @@ import os
 import shutil
 import sys
 import tempfile
+import socket
 
 import ceph
 from charmhelpers.core.hookenv import (
@@ -73,6 +74,12 @@ def install():
     install_upstart_scripts()
 
 
+def az_info():
+    az_info = os.environ.get('JUJU_AVAILABILITY_ZONE')
+    log("AZ Info: " + az_info)
+    return az_info
+
+
 def emit_cephconf():
     mon_hosts = get_mon_hosts()
     log('Monitor hosts are ' + repr(mon_hosts))
@@ -103,6 +110,10 @@ def emit_cephconf():
         if not cluster_network:
             cephcontext['cluster_addr'] = dynamic_ipv6_address
 
+    if az_info():
+        cephcontext['crush_location'] = "root=default rack={} host={}" \
+            .format(az_info(), socket.gethostname())
+
     # Install ceph.conf as an alternative to support
     # co-existence with other charms that write this file
     charm_ceph_conf = "/var/lib/charm/{}/ceph.conf".format(service_name())

templates/ceph.conf

@@ -29,6 +29,10 @@ public addr = {{ public_addr }}
 cluster addr = {{ cluster_addr }}
 {%- endif %}
 
+{% if crush_location %}
+osd crush location = {{crush_location}}
+{% endif %}
+
 
 [mon]
 keyring = /var/lib/ceph/mon/$cluster-$id/keyring