feat(eventProcessor): Add EventProcessor and BatchEventProcessor (#203)

optimizely/event/event_processor.py

@@ -0,0 +1,269 @@
+# Copyright 2019 Optimizely
+# 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.
+
+import abc
+import threading
+import time
+
+from datetime import timedelta
+from six.moves import queue
+
+from optimizely import logger as _logging
+from optimizely.event_dispatcher import EventDispatcher as default_event_dispatcher
+from optimizely.helpers import validator
+from .event_factory import EventFactory
+from .user_event import UserEvent
+
+ABC = abc.ABCMeta('ABC', (object,), {'__slots__': ()})
+
+
+class BaseEventProcessor(ABC):
+  """ Class encapsulating event processing. Override with your own implementation. """
+
+  @abc.abstractmethod
+  def process(user_event):
+    """ Method to provide intermediary processing stage within event production.
+    Args:
+      user_event: UserEvent instance that needs to be processed and dispatched.
+    """
+    pass
+
+
+class BatchEventProcessor(BaseEventProcessor):
+  """
+  BatchEventProcessor is an implementation of the BaseEventProcessor that batches events.
+  The BatchEventProcessor maintains a single consumer thread that pulls events off of
+  the blocking queue and buffers them for either a configured batch size or for a
+  maximum duration before the resulting LogEvent is sent to the EventDispatcher.
+  """
+
+  _DEFAULT_QUEUE_CAPACITY = 1000
+  _DEFAULT_BATCH_SIZE = 10
+  _DEFAULT_FLUSH_INTERVAL = timedelta(seconds=30)
+  _DEFAULT_TIMEOUT_INTERVAL = timedelta(seconds=5)
+  _SHUTDOWN_SIGNAL = object()
+  _FLUSH_SIGNAL = object()
+  LOCK = threading.Lock()
+
+  def __init__(self,
+               event_dispatcher,
+               logger,
+               start_on_init=False,
+               event_queue=None,
+               batch_size=None,
+               flush_interval=None,
+               timeout_interval=None):
+    """ BatchEventProcessor init method to configure event batching.
+    Args:
+      event_dispatcher: Provides a dispatch_event method which if given a URL and params sends a request to it.
+      logger: Provides a log method to log messages. By default nothing would be logged.
+      start_on_init: Optional boolean param which starts the consumer thread if set to True.
+                     Default value is False.
+      event_queue: Optional component which accumulates the events until dispacthed.
+      batch_size: Optional param which defines the upper limit on the number of events in event_queue after which
+                  the event_queue will be flushed.
+      flush_interval: Optional floating point number representing time interval in seconds after which event_queue will
+                      be flushed.
+      timeout_interval: Optional floating point number representing time interval in seconds before joining the consumer
+                        thread.
+    """
+    self.event_dispatcher = event_dispatcher or default_event_dispatcher
+    self.logger = _logging.adapt_logger(logger or _logging.NoOpLogger())
+    self.event_queue = event_queue or queue.Queue(maxsize=self._DEFAULT_QUEUE_CAPACITY)
+    self.batch_size = batch_size if self._validate_intantiation_props(batch_size, 'batch_size') \
+                        else self._DEFAULT_BATCH_SIZE
+    self.flush_interval = timedelta(seconds=flush_interval) \
+                            if self._validate_intantiation_props(flush_interval, 'flush_interval') \
+                            else self._DEFAULT_FLUSH_INTERVAL
+    self.timeout_interval = timedelta(seconds=timeout_interval) \
+                              if self._validate_intantiation_props(timeout_interval, 'timeout_interval') \
+                              else self._DEFAULT_TIMEOUT_INTERVAL
+    self._current_batch = list()
+
+    if start_on_init is True:
+      self.start()
+
+  @property
+  def is_running(self):
+    """ Property to check if consumer thread is alive or not. """
+    return self.executor.isAlive()
+
+  def _validate_intantiation_props(self, prop, prop_name):
+    """ Method to determine if instantiation properties like batch_size, flush_interval
+    and timeout_interval are valid.
+
+    Args:
+      prop: Property value that needs to be validated.
+      prop_name: Property name.
+
+    Returns:
+      False if property value is None or less than 1 or not a finite number.
+      False if property name is batch_size and value is a floating point number.
+      True otherwise.
+    """
+    if (prop_name == 'batch_size' and not isinstance(prop, int)) or prop is None or prop < 1 or \
+      not validator.is_finite_number(prop):
+      self.logger.info('Using default value for {}.'.format(prop_name))
+      return False
+
+    return True
+
+  def _get_time(self, _time=None):
+    """ Method to return rounded off time as integer in seconds. If _time is None, uses current time.
+
+    Args:
+      _time: time in seconds that needs to be rounded off.
+
+    Returns:
+      Integer time in seconds.
+    """
+    if _time is None:
+      return int(round(time.time()))
+
+    return int(round(_time))
+
+  def start(self):
+    """ Starts the batch processing thread to batch events. """
+    if hasattr(self, 'executor') and self.is_running:
+      self.logger.warning('BatchEventProcessor already started.')
+      return
+
+    self.flushing_interval_deadline = self._get_time() + self._get_time(self.flush_interval.total_seconds())
+    self.executor = threading.Thread(target=self._run)
+    self.executor.setDaemon(True)
+    self.executor.start()
+
+  def _run(self):
+    """ Triggered as part of the thread which batches events or flushes event_queue and sleeps
+    periodically if queue is empty.
+    """
+    try:
+      while True:
+        if self._get_time() > self.flushing_interval_deadline:
+          self._flush_queue()
+
+        try:
+          item = self.event_queue.get(True, 0.05)
+
+        except queue.Empty:
+          time.sleep(0.05)
+          continue
+
+        if item == self._SHUTDOWN_SIGNAL:
+          self.logger.debug('Received shutdown signal.')
+          break
+
+        if item == self._FLUSH_SIGNAL:
+          self.logger.debug('Received flush signal.')
+          self._flush_queue()
+          continue
+
+        if isinstance(item, UserEvent):
+          self._add_to_batch(item)
+
+    except Exception as exception:
+      self.logger.error('Uncaught exception processing buffer. Error: ' + str(exception))
+
+    finally:
+      self.logger.info('Exiting processing loop. Attempting to flush pending events.')
+      self._flush_queue()
+
+  def flush(self):
+    """ Adds flush signal to event_queue. """
+
+    self.event_queue.put(self._FLUSH_SIGNAL)
+
+  def _flush_queue(self):
+    """ Flushes event_queue by dispatching events. """
+
+    if len(self._current_batch) == 0:
+      return
+
+    with self.LOCK:
+      to_process_batch = list(self._current_batch)
+      self._current_batch = list()
+
+    log_event = EventFactory.create_log_event(to_process_batch, self.logger)
+
+    try:
+      self.event_dispatcher.dispatch_event(log_event)
+    except Exception as e:
+      self.logger.error('Error dispatching event: ' + str(log_event) + ' ' + str(e))
+
+  def process(self, user_event):
+    """ Method to process the user_event by putting it in event_queue.
+    Args:
+      user_event: UserEvent Instance.
+    """
+    if not isinstance(user_event, UserEvent):
+      self.logger.error('Provided event is in an invalid format.')
+      return
+
+    self.logger.debug('Received user_event: ' + str(user_event))
+
+    try:
+      self.event_queue.put_nowait(user_event)
+    except queue.Full:
+      self.logger.debug('Payload not accepted by the queue. Current size: {}'.format(str(self.event_queue.qsize())))
+
+  def _add_to_batch(self, user_event):
+    """ Method to append received user event to current batch.
+    Args:
+      user_event: UserEvent Instance.
+    """
+    if self._should_split(user_event):
+      self._flush_queue()
+      self._current_batch = list()
+
+    # Reset the deadline if starting a new batch.
+    if len(self._current_batch) == 0:
+      self.flushing_interval_deadline = self._get_time() + \
+        self._get_time(self.flush_interval.total_seconds())
+
+    with self.LOCK:
+      self._current_batch.append(user_event)
+    if len(self._current_batch) >= self.batch_size:
+      self._flush_queue()
+
+  def _should_split(self, user_event):
+    """ Method to check if current event batch should split into two.
+    Args:
+      user_event: UserEvent Instance.
+    Return Value:
+      - True, if revision number and project_id of last event in current batch do not match received event's
+      revision number and project id respectively.
+      - False, otherwise.
+    """
+    if len(self._current_batch) == 0:
+      return False
+
+    current_context = self._current_batch[-1].event_context
+    new_context = user_event.event_context
+
+    if current_context.revision != new_context.revision:
+      return True
+
+    if current_context.project_id != new_context.project_id:
+      return True
+
+    return False
+
+  def stop(self):
+    """ Stops and disposes batch event processor. """
+    self.event_queue.put(self._SHUTDOWN_SIGNAL)
+    self.logger.warning('Stopping Scheduler.')
+
+    self.executor.join(self.timeout_interval.total_seconds())
+
+    if self.is_running:
+      self.logger.error('Timeout exceeded while attempting to close for ' + str(self.timeout_interval) + ' ms.')

optimizely/event/log_event.py

@@ -20,3 +20,6 @@ def __init__(self, url, params, http_verb=None, headers=None):
     self.params = params
     self.http_verb = http_verb or 'POST'
     self.headers = headers
+
+  def __str__(self):
+    return str(self.__class__) + ": " + str(self.__dict__)