Making the switch to v2

lib/ansible/plugins/cache/redis.py

@@ -0,0 +1,102 @@
+# (c) 2014, Brian Coca, Josh Drake, et al
+#
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+# FIXME: can we store these as something else before we ship it?
+import sys
+import time
+import json
+
+from ansible import constants as C
+from ansible.plugins.cache.base import BaseCacheModule
+
+try:
+    from redis import StrictRedis
+except ImportError:
+    print("The 'redis' python module is required, 'pip install redis'")
+    sys.exit(1)
+
+class CacheModule(BaseCacheModule):
+    """
+    A caching module backed by redis.
+
+    Keys are maintained in a zset with their score being the timestamp
+    when they are inserted. This allows for the usage of 'zremrangebyscore'
+    to expire keys. This mechanism is used or a pattern matched 'scan' for
+    performance.
+    """
+    def __init__(self, *args, **kwargs):
+        if C.CACHE_PLUGIN_CONNECTION:
+            connection = C.CACHE_PLUGIN_CONNECTION.split(':')
+        else:
+            connection = []
+
+        self._timeout = float(C.CACHE_PLUGIN_TIMEOUT)
+        self._prefix = C.CACHE_PLUGIN_PREFIX
+        self._cache = StrictRedis(*connection)
+        self._keys_set = 'ansible_cache_keys'
+
+    def _make_key(self, key):
+        return self._prefix + key
+
+    def get(self, key):
+        value = self._cache.get(self._make_key(key))
+        # guard against the key not being removed from the zset;
+        # this could happen in cases where the timeout value is changed
+        # between invocations
+        if value is None:
+            self.delete(key)
+            raise KeyError
+        return json.loads(value)
+
+    def set(self, key, value):
+        value2 = json.dumps(value)
+        if self._timeout > 0: # a timeout of 0 is handled as meaning 'never expire'
+            self._cache.setex(self._make_key(key), int(self._timeout), value2)
+        else:
+            self._cache.set(self._make_key(key), value2)
+
+        self._cache.zadd(self._keys_set, time.time(), key)
+
+    def _expire_keys(self):
+        if self._timeout > 0:
+            expiry_age = time.time() - self._timeout
+        self._cache.zremrangebyscore(self._keys_set, 0, expiry_age)
+
+    def keys(self):
+        self._expire_keys()
+        return self._cache.zrange(self._keys_set, 0, -1)
+
+    def contains(self, key):
+        self._expire_keys()
+        return (self._cache.zrank(self._keys_set, key) >= 0)
+
+    def delete(self, key):
+        self._cache.delete(self._make_key(key))
+        self._cache.zrem(self._keys_set, key)
+
+    def flush(self):
+        for key in self.keys():
+            self.delete(key)
+
+    def copy(self):
+        # FIXME: there is probably a better way to do this in redis
+        ret = dict()
+        for key in self.keys():
+            ret[key] = self.get(key)
+        return ret