set unique galera server-id

Each slave in a mysql replication cluster needs to have a unique
'server-id' set. This is an arbitrary integer, and often people select
1,2,3 etc. For easy deterministic uniqueness without needing to look at
what you've already used, a simple filter has been created to allow for
the hostname to be converted into an integer.

The server ID variable has been added to the my.cnf.j2 template
and the galera_server defaults/main.yml file. The generation of the
server-id variable happens within the `galera-install.yml` play making
it so there is no future impact in role requires.

Change-Id: Id15149e59cb03ab268bb3b7eeaf391334dfc0c01
Fixes-Bug: #1479484

playbooks/galera-install.yml

@@ -72,6 +72,7 @@
       tags:
         - "system-crontab-coordination"
   vars:
+    galera_server_id: "{{ inventory_hostname | string_2_int }}"
     galera_wsrep_node_name: "{{ container_name }}"
     galera_lb_address: "{{ internal_lb_vip_address }}"
     ansible_hostname: "{{ container_name }}"

playbooks/plugins/filters/osa-filters.py

@@ -15,6 +15,7 @@
 # (c) 2015, Kevin Carter <kevin.carter@rackspace.com>
 
 import urlparse
+import hashlib
 
 
 """Filter usage:
@@ -88,6 +89,25 @@ def get_netorigin(url):
         return '%s://%s' % (scheme, netloc)
 
 
+def string_2_int(string):
+    """Return the an integer from a string.
+
+    The string is hashed, converted to a base36 int, and the modulo of 10240
+    is returned.
+
+    :param string: string to retrieve an int from
+    :type string: ``str``
+    :returns: ``int``
+    """
+    # Try to encode utf-8 else pass
+    try:
+        string = string.encode('utf-8')
+    except AttributeError:
+        pass
+    hashed_name = hashlib.sha256(string).hexdigest()
+    return int(hashed_name, 36) % 10240
+
+
 class FilterModule(object):
     """Ansible jinja2 filters."""
 
@@ -97,5 +117,6 @@ class FilterModule(object):
             'bit_length_power_of_2': bit_length_power_of_2,
             'netloc': get_netloc,
             'netloc_no_port': get_netloc_no_port,
-            'netorigin': get_netorigin
+            'netorigin': get_netorigin,
+            'string_2_int': string_2_int
         }

playbooks/roles/galera_server/defaults/main.yml

@@ -20,6 +20,13 @@ galera_lb_address: 127.0.0.1
 
 galera_cluster_name: openstack_galera_cluster
 
+# The galera server-id should be set on all cluster nodes to ensure
+#  that replication is handled correctly and the error
+#  "Warning: You should set server-id to a non-0 value if master_host is
+#   set; we will force server id to 2, but this MySQL server will not act
+#   as a slave." is no longer present.
+# galera_server_id: 0
+
 galera_existing_cluster: true
 galera_running_and_bootstrapped: false
 

playbooks/roles/galera_server/templates/my.cnf.j2

@@ -27,6 +27,9 @@ collation-server = utf8_unicode_ci
 init-connect = 'SET NAMES utf8'
 character-set-server = utf8
 datadir = /var/lib/mysql
+{% if galera_server_id is defined %}
+server-id = {{ galera_server_id }}
+{% endif %}
 
 # LOGGING #
 log-queries-not-using-indexes = {{ galera_unindexed_query_logging }}