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Diffstat (limited to 'kafka/context.py')
| -rw-r--r-- | kafka/context.py | 178 |
1 files changed, 0 insertions, 178 deletions
diff --git a/kafka/context.py b/kafka/context.py deleted file mode 100644 index 1ebc71d..0000000 --- a/kafka/context.py +++ /dev/null @@ -1,178 +0,0 @@ -""" -Context manager to commit/rollback consumer offsets. -""" -from __future__ import absolute_import - -from logging import getLogger - -from kafka.errors import check_error, OffsetOutOfRangeError -from kafka.structs import OffsetCommitRequestPayload - - -class OffsetCommitContext(object): - """ - Provides commit/rollback semantics around a `SimpleConsumer`. - - Usage assumes that `auto_commit` is disabled, that messages are consumed in - batches, and that the consuming process will record its own successful - processing of each message. Both the commit and rollback operations respect - a "high-water mark" to ensure that last unsuccessfully processed message - will be retried. - - Example: - - .. code:: python - - consumer = SimpleConsumer(client, group, topic, auto_commit=False) - consumer.provide_partition_info() - consumer.fetch_last_known_offsets() - - while some_condition: - with OffsetCommitContext(consumer) as context: - messages = consumer.get_messages(count, block=False) - - for partition, message in messages: - if can_process(message): - context.mark(partition, message.offset) - else: - break - - if not context: - sleep(delay) - - - These semantics allow for deferred message processing (e.g. if `can_process` - compares message time to clock time) and for repeated processing of the last - unsuccessful message (until some external error is resolved). - """ - - def __init__(self, consumer): - """ - :param consumer: an instance of `SimpleConsumer` - """ - self.consumer = consumer - self.initial_offsets = None - self.high_water_mark = None - self.logger = getLogger("kafka.context") - - def mark(self, partition, offset): - """ - Set the high-water mark in the current context. - - In order to know the current partition, it is helpful to initialize - the consumer to provide partition info via: - - .. code:: python - - consumer.provide_partition_info() - - """ - max_offset = max(offset + 1, self.high_water_mark.get(partition, 0)) - - self.logger.debug("Setting high-water mark to: %s", - {partition: max_offset}) - - self.high_water_mark[partition] = max_offset - - def __nonzero__(self): - """ - Return whether any operations were marked in the context. - """ - return bool(self.high_water_mark) - - def __enter__(self): - """ - Start a new context: - - - Record the initial offsets for rollback - - Reset the high-water mark - """ - self.initial_offsets = dict(self.consumer.offsets) - self.high_water_mark = dict() - - self.logger.debug("Starting context at: %s", self.initial_offsets) - - return self - - def __exit__(self, exc_type, exc_value, traceback): - """ - End a context. - - - If there was no exception, commit up to the current high-water mark. - - If there was an offset of range error, attempt to find the correct - initial offset. - - If there was any other error, roll back to the initial offsets. - """ - if exc_type is None: - self.commit() - elif isinstance(exc_value, OffsetOutOfRangeError): - self.handle_out_of_range() - return True - else: - self.rollback() - - def commit(self): - """ - Commit this context's offsets: - - - If the high-water mark has moved, commit up to and position the - consumer at the high-water mark. - - Otherwise, reset to the consumer to the initial offsets. - """ - if self.high_water_mark: - self.logger.info("Committing offsets: %s", self.high_water_mark) - self.commit_partition_offsets(self.high_water_mark) - self.update_consumer_offsets(self.high_water_mark) - else: - self.update_consumer_offsets(self.initial_offsets) - - def rollback(self): - """ - Rollback this context: - - - Position the consumer at the initial offsets. - """ - self.logger.info("Rolling back context: %s", self.initial_offsets) - self.update_consumer_offsets(self.initial_offsets) - - def commit_partition_offsets(self, partition_offsets): - """ - Commit explicit partition/offset pairs. - """ - self.logger.debug("Committing partition offsets: %s", partition_offsets) - - commit_requests = [ - OffsetCommitRequestPayload(self.consumer.topic, partition, offset, None) - for partition, offset in partition_offsets.items() - ] - commit_responses = self.consumer.client.send_offset_commit_request( - self.consumer.group, - commit_requests, - ) - for commit_response in commit_responses: - check_error(commit_response) - - def update_consumer_offsets(self, partition_offsets): - """ - Update consumer offsets to explicit positions. - """ - self.logger.debug("Updating consumer offsets to: %s", partition_offsets) - - for partition, offset in partition_offsets.items(): - self.consumer.offsets[partition] = offset - - # consumer keeps other offset states beyond its `offsets` dictionary, - # a relative seek with zero delta forces the consumer to reset to the - # current value of the `offsets` dictionary - self.consumer.seek(0, 1) - - def handle_out_of_range(self): - """ - Handle out of range condition by seeking to the beginning of valid - ranges. - - This assumes that an out of range doesn't happen by seeking past the end - of valid ranges -- which is far less likely. - """ - self.logger.info("Seeking beginning of partition on out of range error") - self.consumer.seek(0, 0) |