Treat postgres settings parameter names as case insensitive (#650)

Because they are indeed case insensitive.
Most of the parameters have snake_case_name, but there are three exceptions from this rule: DateStyle, IntervalStyle and TimeZone.
In fact, if you specify timezone = 'some/tzn' it still works, but Patroni wasn't able to find 'timezone' in pg_settings and stripping this parameter out.

We will use CaseInsensitiveDict to keep postgresql.parameters. This change affects only "final" configuration. That means if you put some"duplicates" (work_mem vs WORK_MEM) into patroni yaml or into cluster config, it would be resolved only at the last stage and for example you will be able to see both values if you use `patronictl edit-config`.

Fixes https://github.com/zalando/patroni/issues/649

patroni/config.py

@@ -10,6 +10,7 @@ from copy import deepcopy
 from patroni.dcs import ClusterConfig
 from patroni.postgresql import Postgresql
 from patroni.utils import deep_compare, parse_int, patch_config
+from requests.structures import CaseInsensitiveDict
 
 logger = logging.getLogger(__name__)
 
@@ -47,7 +48,7 @@ class Config(object):
         'postgresql': {
             'bin_dir': '',
             'use_slots': True,
-            'parameters': {p: v[0] for p, v in Postgresql.CMDLINE_OPTIONS.items()}
+            'parameters': CaseInsensitiveDict({p: v[0] for p, v in Postgresql.CMDLINE_OPTIONS.items()})
         },
         'watchdog': {
             'mode': 'automatic',

patroni/postgresql.py

@@ -15,6 +15,7 @@ from patroni.callback_executor import CallbackExecutor
 from patroni.exceptions import PostgresConnectionException, PostgresException
 from patroni.utils import compare_values, parse_bool, parse_int, Retry, RetryFailedError, polling_loop, split_host_port
 from patroni.postmaster import PostmasterProcess
+from requests.structures import CaseInsensitiveDict
 from six import string_types
 from six.moves.urllib.parse import quote_plus
 from threading import current_thread, Lock
@@ -86,7 +87,7 @@ class Postgresql(object):
     #    default_value -- some sane default value
     #    check_function -- if the new value is not correct must return `!False`
     #    min_version -- major version of PostgreSQL when parameter was introduced
-    CMDLINE_OPTIONS = {
+    CMDLINE_OPTIONS = CaseInsensitiveDict({
         'listen_addresses': (None, lambda _: False, 90100),
         'port': (None, lambda _: False, 90100),
         'cluster_name': (None, lambda _: False, 90500),
@@ -101,7 +102,7 @@ class Postgresql(object):
         'max_replication_slots': (10, lambda v: int(v) >= 10, 90400),
         'max_worker_processes': (8, lambda v: int(v) >= 8, 90400),
         'wal_log_hints': ('on', lambda _: False, 90400)
-    }
+    })
 
     _CONFIG_WARNING_HEADER = '# Do not edit this file manually!\n# It will be overwritten by Patroni!\n'
 
@@ -241,11 +242,9 @@ class Postgresql(object):
                 parameters['synchronous_standby_names'] = self._synchronous_standby_names
         if self._major_version >= 90600 and parameters['wal_level'] == 'hot_standby':
             parameters['wal_level'] = 'replica'
-        ret = {k: v for k, v in parameters.items() if not self._major_version or
-               self._major_version >= self.CMDLINE_OPTIONS.get(k, (0, 1, 90100))[2]}
-        for k in ('hba_file', 'ident_file'):
-            if k in ret:
-                ret[k] = os.path.join(self._config_dir, ret[k])
+        ret = CaseInsensitiveDict({k: v for k, v in parameters.items() if not self._major_version or
+                                   self._major_version >= self.CMDLINE_OPTIONS.get(k, (0, 1, 90100))[2]})
+        ret.update({k: os.path.join(self._config_dir, ret[k]) for k in ('hba_file', 'ident_file') if k in ret})
         return ret
 
     def resolve_connection_addresses(self):
@@ -310,16 +309,16 @@ class Postgresql(object):
 
         conf_changed = hba_changed = local_connection_address_changed = pending_restart = False
         if self.state == 'running':
-            changes = {p: v for p, v in server_parameters.items() if '.' not in p}
-            changes.update({p: None for p, v in self._server_parameters.items() if not ('.' in p or p in changes)})
+            changes = CaseInsensitiveDict({p: v for p, v in server_parameters.items() if '.' not in p})
+            changes.update({p: None for p in self._server_parameters.keys() if not ('.' in p or p in changes)})
             if changes:
                 if 'wal_segment_size' not in changes:
                     changes['wal_segment_size'] = '16384kB'
                 # XXX: query can raise an exception
                 for r in self.query("""SELECT name, setting, unit, vartype, context
                                          FROM pg_settings
-                                        WHERE name IN (""" + ', '.join(['%s'] * len(changes)) + """)
-                                        ORDER BY 1 DESC""", *(list(changes.keys()))):
+                                        WHERE LOWER(name) IN (""" + ', '.join(['%s'] * len(changes)) + """)
+                                        ORDER BY 1 DESC""", *(k.lower() for k in changes.keys())):
                     if r[4] == 'internal':
                         if r[0] == 'wal_segment_size':
                             server_parameters.pop(r[0], None)