Expose memcache coord. class constants

These constants are quite useful to have show up in
the generated docs and do no harm if they are made public
since they are expected to be constant so make them public
and add docstrings to them so they appear in the docs.

Change-Id: Ife77f7dd32d26428a58605ca4cc2d1e6e2abe88d

1 files changed, 28 insertions, 15 deletions

diff --git a/tooz/drivers/memcached.py b/tooz/drivers/memcached.py
index 414e7f4..4bac42f 100644
--- a/tooz/drivers/memcached.py
+++ b/tooz/drivers/memcached.py
@@ -127,10 +127,23 @@ class MemcachedDriver(coordination.CoordinationDriver):
     .. _msgpack: http://msgpack.org/
     """
 
-    _GROUP_PREFIX = b'_TOOZ_GROUP_'
-    _GROUP_LEADER_PREFIX = b'_TOOZ_GROUP_LEADER_'
-    _MEMBER_PREFIX = b'_TOOZ_MEMBER_'
-    _GROUP_LIST_KEY = b'_TOOZ_GROUP_LIST'
+    #: Key prefix attached to groups (used in name-spacing keys)
+    GROUP_PREFIX = b'_TOOZ_GROUP_'
+
+    #: Key prefix attached to leaders of groups (used in name-spacing keys)
+    GROUP_LEADER_PREFIX = b'_TOOZ_GROUP_LEADER_'
+
+    #: Key prefix attached to members of groups (used in name-spacing keys)
+    MEMBER_PREFIX = b'_TOOZ_MEMBER_'
+
+    #: Key where all groups 'known' are stored.
+    GROUP_LIST_KEY = b'_TOOZ_GROUP_LIST'
+
+    #: Default socket/lock/member/leader timeout used when none is provided.
+    DEFAULT_TIMEOUT = 30
+
+    #: String used to keep a key/member alive (until it next expires).
+    STILL_ALIVE = b"It's alive!"
 
     def __init__(self, member_id, parsed_url, options):
         super(MemcachedDriver, self).__init__()
@@ -141,7 +154,7 @@ class MemcachedDriver(coordination.CoordinationDriver):
         self._executor = None
         self.host = (parsed_url.hostname or "localhost",
                      parsed_url.port or 11211)
-        default_timeout = options.get('timeout', '30')
+        default_timeout = options.get('timeout', self.DEFAULT_TIMEOUT)
         self.timeout = int(default_timeout)
         self.membership_timeout = int(options.get(
             'membership_timeout', default_timeout))
@@ -205,13 +218,13 @@ class MemcachedDriver(coordination.CoordinationDriver):
         self.client.close()
 
     def _encode_group_id(self, group_id):
-        return self._GROUP_PREFIX + group_id
+        return self.GROUP_PREFIX + group_id
 
     def _encode_member_id(self, member_id):
-        return self._MEMBER_PREFIX + member_id
+        return self.MEMBER_PREFIX + member_id
 
     def _encode_group_leader(self, group_id):
-        return self._GROUP_LEADER_PREFIX + group_id
+        return self.GROUP_LEADER_PREFIX + group_id
 
     @_retry.retry()
     def _add_group_to_group_list(self, group_id):
@@ -219,16 +232,16 @@ class MemcachedDriver(coordination.CoordinationDriver):
 
         :param group_id: The group id
         """
-        group_list, cas = self.client.gets(self._GROUP_LIST_KEY)
+        group_list, cas = self.client.gets(self.GROUP_LIST_KEY)
         if cas:
             group_list = set(group_list)
             group_list.add(group_id)
-            if not self.client.cas(self._GROUP_LIST_KEY,
+            if not self.client.cas(self.GROUP_LIST_KEY,
                                    list(group_list), cas):
                 # Someone updated the group list before us, try again!
                 raise _retry.Retry
         else:
-            if not self.client.add(self._GROUP_LIST_KEY,
+            if not self.client.add(self.GROUP_LIST_KEY,
                                    [group_id], noreply=False):
                 # Someone updated the group list before us, try again!
                 raise _retry.Retry
@@ -239,10 +252,10 @@ class MemcachedDriver(coordination.CoordinationDriver):
 
         :param group_id: The group id
         """
-        group_list, cas = self.client.gets(self._GROUP_LIST_KEY)
+        group_list, cas = self.client.gets(self.GROUP_LIST_KEY)
         group_list = set(group_list)
         group_list.remove(group_id)
-        if not self.client.cas(self._GROUP_LIST_KEY,
+        if not self.client.cas(self.GROUP_LIST_KEY,
                                list(group_list), cas):
             # Someone updated the group list before us, try again!
             raise _retry.Retry
@@ -262,7 +275,7 @@ class MemcachedDriver(coordination.CoordinationDriver):
 
         @_translate_failures
         def _get_groups():
-            return self.client.get(self._GROUP_LIST_KEY) or []
+            return self.client.get(self.GROUP_LIST_KEY) or []
 
         return MemcachedFutureResult(self._executor.submit(_get_groups))
 
@@ -397,7 +410,7 @@ class MemcachedDriver(coordination.CoordinationDriver):
     @_translate_failures
     def heartbeat(self):
         self.client.set(self._encode_member_id(self._member_id),
-                        "It's alive!",
+                        self.STILL_ALIVE,
                         expire=self.membership_timeout)
         # Reset the acquired locks
         for lock in self._acquired_locks: