Add availability_zone to the OSD configuration

Addition of configurable availability_zone allows the
administrator to deploy Ceph with two dimensions of
crush locations, one from config and one from Juju's
availability zone

Change-Id: Icd0ee2eeaea8bad2b78f2ed46176084e01601261

config.yaml

@@ -191,10 +191,21 @@ options:
                 kernel.threads-max: 2097152 }'
     description: |
       YAML-formatted associative array of sysctl key/value pairs to be set
-      persistently. By default we set pid_max, max_map_count and 
+      persistently. By default we set pid_max, max_map_count and
       threads-max to a high value to avoid problems with large numbers (>20)
       of OSDs recovering. very large clusters should set those values even
       higher (e.g. max for kernel.pid_max is 4194303).
+  customize-failure-domain:
+    type: boolean
+    default: false
+    description: |
+      Setting this to true will tell Ceph to replicate across Juju's
+      Availability Zone instead of specifically by host.
+  availability_zone:
+    type: string
+    default: 
+    description: |
+      Custom availablility zone to provide to Ceph for the OSD placement
   nagios_context:
     type: string
     default: "juju"

hooks/ceph_hooks.py

@@ -16,6 +16,7 @@
 
 import os
 import sys
+import socket
 
 sys.path.append('lib')
 import ceph
@@ -150,6 +151,19 @@ def install():
     apt_install(packages=ceph.PACKAGES, fatal=True)
 
 
+def az_info():
+    az_info = ""
+    juju_az_info = os.environ.get('JUJU_AVAILABILITY_ZONE')
+    if juju_az_info:
+        az_info = "{} juju_availability_zone={}".format(az_info, juju_az_info)
+    config_az = config("availability_zone")
+    if config_az:
+        az_info = "{} config_availability_zone={}".format(az_info, config_az)
+    if az_info != "":
+        log("AZ Info: " + az_info)
+        return az_info
+
+
 def use_short_objects():
     '''
     Determine whether OSD's should be configured with
@@ -199,6 +213,17 @@ def get_ceph_context():
         cephcontext['public_addr'] = get_public_addr()
         cephcontext['cluster_addr'] = get_cluster_addr()
 
+    if config('customize-failure-domain'):
+        az = az_info()
+        if az:
+            cephcontext['crush_location'] = "root=default {} host={}" \
+                .format(az, socket.gethostname())
+        else:
+            log(
+                "Your Juju environment doesn't"
+                "have support for Availability Zones"
+            )
+
     # NOTE(dosaboy): these sections must correspond to what is supported in the
     #                config template.
     sections = ['global', 'mds', 'osd', 'mon']

unit_tests/test_ceph_hooks.py

@@ -29,7 +29,8 @@ CHARM_CONFIG = {'config-flags': '',
                 'osd-journal-size': 1024,
                 'use-direct-io': True,
                 'osd-format': 'ext4',
-                'prefer-ipv6': False}
+                'prefer-ipv6': False,
+                'customize-failure-domain': False}
 
 
 class CephHooksTestCase(unittest.TestCase):