Add an option to allow MySQL service to log to syslog.

This patch provides one of the alternative solution to address the
problem that the error log might grow too large.

Closes-bug: #1812950
Change-Id: If7c0c71492eb30f24cbcc03ca05a67e6ea571f4e

config.yaml

@@ -177,6 +177,12 @@ options:
     description: |
       Default multicast port number that will be used to communicate between HA
       Cluster nodes.
+  use-syslog:
+    type: boolean
+    default: False
+    description: |
+      Uses syslog instead of the default error log file (/var/log/mysql/error.log).
+      Setting this to True will allow MySQL service to log to syslog.
   enable-binlogs:
     type: boolean
     default: False

hooks/percona_hooks.py

@@ -268,6 +268,7 @@ def render_config(hosts=None):
         'sst_password': sst_password(),
         'innodb_file_per_table': config('innodb-file-per-table'),
         'table_open_cache': config('table-open-cache'),
+        'use_syslog': config('use-syslog'),
         'binlogs_path': config('binlogs-path'),
         'enable_binlogs': config('enable-binlogs'),
         'binlogs_max_size': config('binlogs-max-size'),

templates/mysqld.cnf

@@ -70,7 +70,13 @@ query_cache_size        = 16M
 #
 # Error log - should be very few entries.
 #
+# Optionally enable syslog instead, addressing bug:
+# https://bugs.launchpad.net/charm-percona-cluster/+bug/1812950
+{% if use_syslog -%}
+log_syslog = {{ use_syslog }}
+{% else -%}
 log_error = /var/log/mysql/error.log
+{% endif %}
 
 #
 # The following can be used as easy to replay backup logs or for replication.

unit_tests/test_percona_hooks.py

@@ -918,6 +918,7 @@ class TestConfigs(CharmTestCase):
             'series_upgrade': hooks.is_unit_upgrading_set(),
             'private_address': '10.1.1.1',
             'cluster_hosts': '',
+            'use_syslog': self.default_config['use-syslog'],
             'enable_binlogs': self.default_config['enable-binlogs'],
             'sst_password': 'sstpassword',
             'myisam_recover': 'BACKUP',
@@ -976,6 +977,7 @@ class TestConfigs(CharmTestCase):
             'private_address': '10.1.1.1',
             'innodb_autoinc_lock_mode': '2',
             'cluster_hosts': '',
+            'use_syslog': self.default_config['use-syslog'],
             'enable_binlogs': self.default_config['enable-binlogs'],
             'sst_password': 'sstpassword',
             'sst_method': self.default_config['sst-method'],
@@ -1042,6 +1044,7 @@ class TestConfigs(CharmTestCase):
             'private_address': '10.1.1.1',
             'innodb_autoinc_lock_mode': '2',
             'cluster_hosts': '',
+            'use_syslog': self.default_config['use-syslog'],
             'enable_binlogs': self.default_config['enable-binlogs'],
             'sst_password': 'sstpassword',
             'sst_method': self.default_config['sst-method'],
@@ -1121,6 +1124,7 @@ class TestConfigs(CharmTestCase):
             'private_address': '10.1.1.1',
             'innodb_autoinc_lock_mode': '2',
             'cluster_hosts': '',
+            'use_syslog': self.default_config['use-syslog'],
             'enable_binlogs': self.default_config['enable-binlogs'],
             'sst_password': 'sstpassword',
             'sst_method': self.default_config['sst-method'],
@@ -1184,6 +1188,7 @@ class TestConfigs(CharmTestCase):
             'private_address': '10.1.1.1',
             'innodb_autoinc_lock_mode': '2',
             'cluster_hosts': '',
+            'use_syslog': self.default_config['use-syslog'],
             'enable_binlogs': self.default_config['enable-binlogs'],
             'sst_password': 'sstpassword',
             'sst_method': self.default_config['sst-method'],