VOL-1101: Implement a Twisted Python shim layer to interface with any KV store
* Current support is for Etcd and Consul only
* kv_client.py describes the interface
* consul_client.py contains the Consul implementation
* etcd_client.py contains the Etcd implementation
* kvstore.py contains a factory function
Change-Id: I895540eda13a78bc755adbba78a5716d7fa59612
diff --git a/common/kvstore/consul_client.py b/common/kvstore/consul_client.py
new file mode 100644
index 0000000..825d673
--- /dev/null
+++ b/common/kvstore/consul_client.py
@@ -0,0 +1,345 @@
+# Copyright 2017-present Open Networking Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from common.kvstore.kv_client import DEFAULT_TIMEOUT, Event, KVClient, KVPair, RETRY_BACKOFF
+from common.utils.asleep import asleep
+from common.utils.deferred_utils import DeferredWithTimeout, TimeOutError
+from consul import ConsulException
+from consul.twisted import Consul
+from structlog import get_logger
+from twisted.internet.defer import inlineCallbacks, returnValue, Deferred
+
+log = get_logger()
+
+class ConsulClient(KVClient):
+
+ def __init__(self, kv_host, kv_port):
+ KVClient.__init__(self, kv_host, kv_port)
+ self.session_id = None
+ self.client = Consul(kv_host, kv_port)
+ self.watcher = None
+
+ @inlineCallbacks
+ def get(self, key, timeout=DEFAULT_TIMEOUT):
+ result = yield self._op_with_retry('GET', key, None, timeout)
+ returnValue(result)
+
+ @inlineCallbacks
+ def list(self, key, timeout=DEFAULT_TIMEOUT):
+ result = yield self._op_with_retry('LIST', key, None, timeout)
+ returnValue(result)
+
+ @inlineCallbacks
+ def put(self, key, value, timeout=DEFAULT_TIMEOUT):
+ _, err = yield self._op_with_retry('PUT', key, value, timeout)
+ returnValue(err)
+
+ @inlineCallbacks
+ def delete(self, key, timeout=DEFAULT_TIMEOUT):
+ _, err = yield self._op_with_retry('DELETE', key, None, timeout)
+ returnValue(err)
+
+ @inlineCallbacks
+ def reserve(self, key, value, ttl, timeout=DEFAULT_TIMEOUT):
+ result = yield self._op_with_retry('RESERVE', key, value, timeout, ttl=ttl)
+ returnValue(result)
+
+ @inlineCallbacks
+ def renew_reservation(self, key, timeout=DEFAULT_TIMEOUT):
+ result, err = yield self._op_with_retry('RENEW', key, None, timeout)
+ returnValue(err)
+
+ @inlineCallbacks
+ def release_reservation(self, key, timeout=DEFAULT_TIMEOUT):
+ result, err = yield self._op_with_retry('RELEASE', key, None, timeout)
+ returnValue(err)
+
+ @inlineCallbacks
+ def release_all_reservations(self, timeout=DEFAULT_TIMEOUT):
+ result, err = yield self._op_with_retry('RELEASE-ALL', None, None, timeout)
+ returnValue(err)
+
+ def watch(self, key, key_change_callback, timeout=DEFAULT_TIMEOUT):
+ self._retriggering_watch(key, key_change_callback, timeout)
+
+ @inlineCallbacks
+ def _retriggering_watch(self, key, key_change_callback, timeout):
+ self.key_watches[key] = ConsulWatch(self.client, key, key_change_callback, timeout)
+ yield self.key_watches[key].start()
+
+ def close_watch(self, key, timeout=DEFAULT_TIMEOUT):
+ if key in self.key_watches:
+ self.key_watches[key].stop()
+
+ @inlineCallbacks
+ def _op_with_retry(self, operation, key, value, timeout, *args, **kw):
+ log.debug('kv-op', operation=operation, key=key, timeout=timeout, args=args, kw=kw)
+ err = None
+ result = None
+ while True:
+ try:
+ if operation == 'GET':
+ result = yield self._get(key, **kw)
+ elif operation == 'LIST':
+ result, err = yield self._list(key)
+ elif operation == 'PUT':
+ # Put returns a boolean response
+ result = yield self.client.kv.put(key, value)
+ if not result:
+ err = 'put-failed'
+ elif operation == 'DELETE':
+ # Delete returns a boolean response
+ result = yield self.client.kv.delete(key)
+ if not result:
+ err = 'delete-failed'
+ elif operation == 'RESERVE':
+ result, err = yield self._reserve(key, value, **kw)
+ elif operation == 'RENEW':
+ result, err = yield self._renew_reservation(key)
+ elif operation == 'RELEASE':
+ result, err = yield self._release_reservation(key)
+ elif operation == 'RELEASE-ALL':
+ err = yield self._release_all_reservations()
+ self._clear_backoff()
+ break
+ except ConsulException as ex:
+ if 'ConnectionRefusedError' in ex.message:
+ log.exception('comms-exception', ex=ex)
+ yield self._backoff('consul-not-up')
+ else:
+ log.error('consul-specific-exception', ex=ex)
+ err = ex
+ except Exception as ex:
+ log.error('consul-exception', ex=ex)
+ err = ex
+
+ if timeout > 0 and self.retry_time > timeout:
+ err = 'operation-timed-out'
+ if err is not None:
+ self._clear_backoff()
+ break
+
+ returnValue((result,err))
+
+ @inlineCallbacks
+ def _get(self, key, **kw):
+ kvp = None
+ index, rec = yield self.client.kv.get(key, **kw)
+ if rec is not None:
+ kvp = KVPair(rec['Key'], rec['Value'], index)
+ returnValue(kvp)
+
+ @inlineCallbacks
+ def _list(self, key):
+ err = None
+ list = []
+ index, recs = yield self.client.kv.get(key, recurse=True)
+ for rec in recs:
+ list.append(KVPair(rec['Key'], rec['Value'], rec['ModifyIndex']))
+ returnValue((list, err))
+
+ @inlineCallbacks
+ def _reserve(self, key, value, **kw):
+ for name, val in kw.items():
+ if name == 'ttl':
+ ttl = val
+ break
+ reserved = False
+ err = 'reservation-failed'
+ owner = None
+
+ # Create a session
+ self.session_id = yield self.client.session.create(behavior='delete',
+ ttl=ttl) # lock_delay=1)
+ log.debug('create-session', id=self.session_id)
+ # Try to acquire the key
+ result = yield self.client.kv.put(key, value, acquire=self.session_id)
+ log.debug('key-acquire', key=key, value=value, sess=self.session_id, result=result)
+
+ # Check if reservation succeeded
+ index, record = yield self.client.kv.get(key)
+ if record is not None and 'Value' in record:
+ owner = record['Value']
+ log.debug('get-key', session=record['Session'], owner=owner)
+ if record['Session'] == self.session_id and owner == value:
+ reserved = True
+ log.debug('key-reserved', key=key, value=value, ttl=ttl)
+ # Add key to reservation list
+ self.key_reservations[key] = self.session_id
+ else:
+ log.debug('reservation-held-by-another', owner=owner)
+
+ if reserved:
+ err = None
+ returnValue((owner, err))
+
+ @inlineCallbacks
+ def _renew_reservation(self, key):
+ result = None
+ err = None
+ if key not in self.key_reservations:
+ err = 'key-not-reserved'
+ else:
+ session_id = self.key_reservations[key]
+ # A successfully renewed session returns an object with fields:
+ # Node, CreateIndex, Name, ModifyIndex, ID, Behavior, TTL,
+ # LockDelay, and Checks
+ result = yield self.client.session.renew(session_id=session_id)
+ log.debug('session-renew', result=result)
+ if result is None:
+ err = 'session-renewal-failed'
+ returnValue((result, err))
+
+ @inlineCallbacks
+ def _release_reservation(self, key):
+ err = None
+ if key not in self.key_reservations:
+ err = 'key-not-reserved'
+ else:
+ session_id = self.key_reservations[key]
+ # A successfully destroyed session returns a boolean result
+ success = yield self.client.session.destroy(session_id)
+ log.debug('session-destroy', result=success)
+ if not success:
+ err = 'session-destroy-failed'
+ self.session_id = None
+ self.key_reservations.pop(key)
+ returnValue((success, err))
+
+ @inlineCallbacks
+ def _release_all_reservations(self):
+ err = None
+ keys_to_delete = []
+ for key in self.key_reservations:
+ session_id = self.key_reservations[key]
+ # A successfully destroyed session returns a boolean result
+ success = yield self.client.session.destroy(session_id)
+ if not success:
+ err = 'session-destroy-failed'
+ log.debug('session-destroy', id=session_id, result=success)
+ self.session_id = None
+ keys_to_delete.append(key)
+ for key in keys_to_delete:
+ self.key_reservations.pop(key)
+ returnValue(err)
+
+
+class ConsulWatch():
+
+ def __init__(self, consul, key, callback, timeout):
+ self.client = consul
+ self.key = key
+ self.index = None
+ self.callback = callback
+ self.timeout = timeout
+ self.period = 60
+ self.running = True
+ self.retries = 0
+ self.retry_time = 0
+
+ @inlineCallbacks
+ def start(self):
+ self.running = True
+ index, rec = yield self._get_with_retry(self.key, None,
+ timeout=self.timeout)
+ self.index = str(index)
+
+ @inlineCallbacks
+ def _get(key, deferred):
+ try:
+ index, rec = yield self._get_with_retry(key, None,
+ timeout=self.timeout,
+ index=self.index)
+ self.index = str(index)
+ if not deferred.called:
+ log.debug('got-result-cancelling-deferred')
+ deferred.callback((self.index, rec))
+ except Exception as e:
+ log.exception('got-exception', e=e)
+
+ while self.running:
+ try:
+ rcvd = DeferredWithTimeout(timeout=self.period)
+ _get(self.key, rcvd)
+ try:
+ # Update index for next watch iteration
+ index, rec = yield rcvd
+ log.debug('event-received', index=index, rec=rec)
+ # Notify client of key change event
+ if rec is None:
+ # Key has been deleted
+ self._send_event(Event(Event.DELETE, self.key, None))
+ else:
+ self._send_event(Event(Event.PUT, rec['Key'], rec['Value']))
+ except TimeOutError as e:
+ log.debug('no-events-over-watch-period', key=self.key)
+ except Exception as e:
+ log.exception('exception', e=e)
+ except Exception as e:
+ log.exception('exception', e=e)
+
+ log.debug('close-watch', key=self.key)
+
+ def stop(self):
+ self.running = False
+ self.callback = None
+
+ @inlineCallbacks
+ def _get_with_retry(self, key, value, timeout, *args, **kw):
+ log.debug('watch-period', key=key, period=self.period, timeout=timeout, args=args, kw=kw)
+ err = None
+ result = None
+ while True:
+ try:
+ result = yield self.client.kv.get(key, **kw)
+ self._clear_backoff()
+ break
+ except ConsulException as ex:
+ err = ex
+ if 'ConnectionRefusedError' in ex.message:
+ self._send_event(Event(Event.CONNECTION_DOWN, self.key, None))
+ log.exception('comms-exception', ex=ex)
+ yield self._backoff('consul-not-up')
+ else:
+ log.error('consul-specific-exception', ex=ex)
+ except Exception as ex:
+ err = ex
+ log.error('consul-exception', ex=ex)
+
+ if timeout > 0 and self.retry_time > timeout:
+ err = 'operation-timed-out'
+ if err is not None:
+ self._clear_backoff()
+ break
+
+ returnValue(result)
+
+ def _send_event(self, event):
+ if self.callback is not None:
+ self.callback(event)
+
+ def _backoff(self, msg):
+ wait_time = RETRY_BACKOFF[min(self.retries, len(RETRY_BACKOFF) - 1)]
+ self.retry_time += wait_time
+ self.retries += 1
+ log.error(msg, next_retry_in_secs=wait_time,
+ total_delay_in_secs = self.retry_time,
+ retries=self.retries)
+ return asleep(wait_time)
+
+ def _clear_backoff(self):
+ if self.retries:
+ log.debug('reconnected-to-kv', after_retries=self.retries)
+ self.retries = 0
+ self.retry_time = 0