Set server_id when using binlogs

Percona-cluster was failing to start when enable-binlogs was set to
True due to missing server_id in the configuration.

Set the server_id to a unique, non-zero, positive number from 1 to
2**32 - 1.

Closes-Bug: #1772947
Change-Id: Id7da6dd8f27e364e0d5244e4ec33ae4645e4ef96

hooks/percona_hooks.py

@@ -110,6 +110,7 @@ from percona_utils import (
     update_root_password,
     cluster_wait,
     get_wsrep_provider_options,
+    get_server_id,
 )
 
 from charmhelpers.core.unitdata import kv
@@ -191,6 +192,7 @@ def render_config(hosts=None):
         'binlogs_expire_days': config('binlogs-expire-days'),
         'performance_schema': config('performance-schema'),
         'is_leader': is_leader(),
+        'server_id': get_server_id(),
     }
 
     if config('prefer-ipv6'):

hooks/percona_utils.py

@@ -1032,3 +1032,23 @@ def get_wsrep_provider_options():
                                       .format(config('peer-timeout')))
 
     return ';'.join(wsrep_provider_options)
+
+
+def get_server_id():
+    """ Return unique server id for bin log replication
+
+    Server ID must be a unique, non-zero, positive number from 1 to 2**32 - 1
+    https://dev.mysql.com/doc/refman/8.0/en/replication-options.html
+
+    :returns: int server_id
+    """
+    MAX_SERVER_ID = 2**32 - 1
+
+    # Get the juju unit number
+    server_id = int(local_unit().split('/')[-1])
+
+    # Server ID of 0 indicates disabled replication, use the max instead
+    if server_id == 0:
+        server_id = MAX_SERVER_ID
+
+    return server_id

templates/my.cnf

@@ -29,6 +29,7 @@ wsrep_cluster_address=gcomm://{{ cluster_hosts }}
 binlog_format=ROW
 
 {% if enable_binlogs -%}
+server_id = {{ server_id }}
 log_bin={{ binlogs_path }}
 expire_logs_days={{ binlogs_expire_days }}
 max_binlog_size={{ binlogs_max_size }}

templates/mysqld.cnf

@@ -73,6 +73,7 @@ log_error = /var/log/mysql/error.log
 # note: if you are setting up a replication slave, see README.Debian about
 #       other settings you may need to change.
 {% if enable_binlogs -%}
+server_id = {{ server_id }}
 log_bin={{ binlogs_path }}
 {% endif %}