from __future__ import absolute_import import copy import logging import time import six from kafka.client_async import KafkaClient from kafka.consumer.fetcher import Fetcher from kafka.consumer.subscription_state import SubscriptionState from kafka.coordinator.consumer import ConsumerCoordinator from kafka.coordinator.assignors.roundrobin import RoundRobinPartitionAssignor from kafka.protocol.offset import OffsetResetStrategy from kafka.version import __version__ log = logging.getLogger(__name__) class KafkaConsumer(six.Iterator): """Consume records from a Kafka cluster. The consumer will transparently handle the failure of servers in the Kafka cluster, and adapt as topic-partitions are created or migrate between brokers. It also interacts with the assigned kafka Group Coordinator node to allow multiple consumers to load balance consumption of topics (requires kafka >= 0.9.0.0). Arguments: *topics (str): optional list of topics to subscribe to. If not set, call subscribe() or assign() before consuming records. Keyword Arguments: bootstrap_servers: 'host[:port]' string (or list of 'host[:port]' strings) that the consumer should contact to bootstrap initial cluster metadata. This does not have to be the full node list. It just needs to have at least one broker that will respond to a Metadata API Request. Default port is 9092. If no servers are specified, will default to localhost:9092. client_id (str): a name for this client. This string is passed in each request to servers and can be used to identify specific server-side log entries that correspond to this client. Also submitted to GroupCoordinator for logging with respect to consumer group administration. Default: 'kafka-python-{version}' group_id (str): name of the consumer group to join for dynamic partition assignment (if enabled), and to use for fetching and committing offsets. Default: 'kafka-python-default-group' key_deserializer (callable): Any callable that takes a raw message key and returns a deserialized key. value_deserializer (callable, optional): Any callable that takes a raw message value and returns a deserialized value. fetch_min_bytes (int): Minimum amount of data the server should return for a fetch request, otherwise wait up to fetch_max_wait_ms for more data to accumulate. Default: 1024. fetch_max_wait_ms (int): The maximum amount of time in milliseconds the server will block before answering the fetch request if there isn't sufficient data to immediately satisfy the requirement given by fetch_min_bytes. Default: 500. max_partition_fetch_bytes (int): The maximum amount of data per-partition the server will return. The maximum total memory used for a request = #partitions * max_partition_fetch_bytes. This size must be at least as large as the maximum message size the server allows or else it is possible for the producer to send messages larger than the consumer can fetch. If that happens, the consumer can get stuck trying to fetch a large message on a certain partition. Default: 1048576. request_timeout_ms (int): Client request timeout in milliseconds. Default: 40000. retry_backoff_ms (int): Milliseconds to backoff when retrying on errors. Default: 100. reconnect_backoff_ms (int): The amount of time in milliseconds to wait before attempting to reconnect to a given host. Default: 50. max_in_flight_requests_per_connection (int): Requests are pipelined to kafka brokers up to this number of maximum requests per broker connection. Default: 5. auto_offset_reset (str): A policy for resetting offsets on OffsetOutOfRange errors: 'earliest' will move to the oldest available message, 'latest' will move to the most recent. Any ofther value will raise the exception. Default: 'latest'. enable_auto_commit (bool): If true the consumer's offset will be periodically committed in the background. Default: True. auto_commit_interval_ms (int): milliseconds between automatic offset commits, if enable_auto_commit is True. Default: 5000. default_offset_commit_callback (callable): called as callback(offsets, response) response will be either an Exception or a OffsetCommitResponse struct. This callback can be used to trigger custom actions when a commit request completes. check_crcs (bool): Automatically check the CRC32 of the records consumed. This ensures no on-the-wire or on-disk corruption to the messages occurred. This check adds some overhead, so it may be disabled in cases seeking extreme performance. Default: True metadata_max_age_ms (int): The period of time in milliseconds after which we force a refresh of metadata even if we haven't seen any partition leadership changes to proactively discover any new brokers or partitions. Default: 300000 partition_assignment_strategy (list): List of objects to use to distribute partition ownership amongst consumer instances when group management is used. Default: [RoundRobinPartitionAssignor] heartbeat_interval_ms (int): The expected time in milliseconds between heartbeats to the consumer coordinator when using Kafka's group management feature. Heartbeats are used to ensure that the consumer's session stays active and to facilitate rebalancing when new consumers join or leave the group. The value must be set lower than session_timeout_ms, but typically should be set no higher than 1/3 of that value. It can be adjusted even lower to control the expected time for normal rebalances. Default: 3000 session_timeout_ms (int): The timeout used to detect failures when using Kafka's group managementment facilities. Default: 30000 send_buffer_bytes (int): The size of the TCP send buffer (SO_SNDBUF) to use when sending data. Default: 131072 receive_buffer_bytes (int): The size of the TCP receive buffer (SO_RCVBUF) to use when reading data. Default: 32768 consumer_timeout_ms (int): number of millisecond to throw a timeout exception to the consumer if no message is available for consumption. Default: -1 (dont throw exception) api_version (str): specify which kafka API version to use. 0.9 enables full group coordination features; 0.8.2 enables kafka-storage offset commits; 0.8.1 enables zookeeper-storage offset commits; 0.8.0 is what is left. If set to 'auto', will attempt to infer the broker version by probing various APIs. Default: auto Note: Configuration parameters are described in more detail at https://kafka.apache.org/090/configuration.html#newconsumerconfigs """ DEFAULT_CONFIG = { 'bootstrap_servers': 'localhost', 'client_id': 'kafka-python-' + __version__, 'group_id': 'kafka-python-default-group', 'key_deserializer': None, 'value_deserializer': None, 'fetch_max_wait_ms': 500, 'fetch_min_bytes': 1024, 'max_partition_fetch_bytes': 1 * 1024 * 1024, 'request_timeout_ms': 40 * 1000, 'retry_backoff_ms': 100, 'reconnect_backoff_ms': 50, 'max_in_flight_requests_per_connection': 5, 'auto_offset_reset': 'latest', 'enable_auto_commit': True, 'auto_commit_interval_ms': 5000, 'check_crcs': True, 'metadata_max_age_ms': 5 * 60 * 1000, 'partition_assignment_strategy': (RoundRobinPartitionAssignor,), 'heartbeat_interval_ms': 3000, 'session_timeout_ms': 30000, 'send_buffer_bytes': 128 * 1024, 'receive_buffer_bytes': 32 * 1024, 'consumer_timeout_ms': -1, 'api_version': 'auto', 'connections_max_idle_ms': 9 * 60 * 1000, # not implemented yet #'metric_reporters': None, #'metrics_num_samples': 2, #'metrics_sample_window_ms': 30000, } def __init__(self, *topics, **configs): self.config = copy.copy(self.DEFAULT_CONFIG) for key in self.config: if key in configs: self.config[key] = configs.pop(key) # Only check for extra config keys in top-level class assert not configs, 'Unrecognized configs: %s' % configs deprecated = {'smallest': 'earliest', 'largest': 'latest' } if self.config['auto_offset_reset'] in deprecated: new_config = deprecated[self.config['auto_offset_reset']] log.warning('use auto_offset_reset=%s (%s is deprecated)', new_config, self.config['auto_offset_reset']) self.config['auto_offset_reset'] = new_config self._client = KafkaClient(**self.config) # Check Broker Version if not set explicitly if self.config['api_version'] == 'auto': self.config['api_version'] = self._client.check_version() assert self.config['api_version'] in ('0.9', '0.8.2', '0.8.1', '0.8.0') # Convert api_version config to tuple for easy comparisons self.config['api_version'] = tuple( map(int, self.config['api_version'].split('.'))) self._subscription = SubscriptionState(self.config['auto_offset_reset']) self._fetcher = Fetcher( self._client, self._subscription, **self.config) self._coordinator = ConsumerCoordinator( self._client, self._subscription, assignors=self.config['partition_assignment_strategy'], **self.config) self._closed = False self._iterator = None self._consumer_timeout = float('inf') #self.metrics = None if topics: self._subscription.subscribe(topics=topics) self._client.set_topics(topics) def assign(self, partitions): """Manually assign a list of TopicPartitions to this consumer. Arguments: partitions (list of TopicPartition): assignment for this instance. Raises: IllegalStateError: if consumer has already called subscribe() Warning: It is not possible to use both manual partition assignment with assign() and group assignment with subscribe(). Note: This interface does not support incremental assignment and will replace the previous assignment (if there was one). Note: Manual topic assignment through this method does not use the consumer's group management functionality. As such, there will be no rebalance operation triggered when group membership or cluster and topic metadata change. """ self._subscription.assign_from_user(partitions) self._client.set_topics([tp.topic for tp in partitions]) def assignment(self): """Get the TopicPartitions currently assigned to this consumer. If partitions were directly assigned using assign(), then this will simply return the same partitions that were previously assigned. If topics were subscribed using subscribe(), then this will give the set of topic partitions currently assigned to the consumer (which may be none if the assignment hasn't happened yet, or if the partitions are in the process of being reassigned). Returns: set: {TopicPartition, ...} """ return self._subscription.assigned_partitions() def close(self): """Close the consumer, waiting indefinitely for any needed cleanup.""" if self._closed: return log.debug("Closing the KafkaConsumer.") self._closed = True self._coordinator.close() #self.metrics.close() self._client.close() try: self.config['key_deserializer'].close() except AttributeError: pass try: self.config['value_deserializer'].close() except AttributeError: pass log.debug("The KafkaConsumer has closed.") def commit_async(self, offsets=None, callback=None): """Commit offsets to kafka asynchronously, optionally firing callback This commits offsets only to Kafka. The offsets committed using this API will be used on the first fetch after every rebalance and also on startup. As such, if you need to store offsets in anything other than Kafka, this API should not be used. This is an asynchronous call and will not block. Any errors encountered are either passed to the callback (if provided) or discarded. Arguments: offsets (dict, optional): {TopicPartition: OffsetAndMetadata} dict to commit with the configured group_id. Defaults to current consumed offsets for all subscribed partitions. callback (callable, optional): called as callback(offsets, response) with response as either an Exception or a OffsetCommitResponse struct. This callback can be used to trigger custom actions when a commit request completes. Returns: kafka.future.Future """ assert self.config['api_version'] >= (0, 8, 1) if offsets is None: offsets = self._subscription.all_consumed_offsets() log.debug("Committing offsets: %s", offsets) future = self._coordinator.commit_offsets_async( offsets, callback=callback) return future def commit(self, offsets=None): """Commit offsets to kafka, blocking until success or error This commits offsets only to Kafka. The offsets committed using this API will be used on the first fetch after every rebalance and also on startup. As such, if you need to store offsets in anything other than Kafka, this API should not be used. Blocks until either the commit succeeds or an unrecoverable error is encountered (in which case it is thrown to the caller). Currently only supports kafka-topic offset storage (not zookeeper) Arguments: offsets (dict, optional): {TopicPartition: OffsetAndMetadata} dict to commit with the configured group_id. Defaults to current consumed offsets for all subscribed partitions. """ assert self.config['api_version'] >= (0, 8, 1) if offsets is None: offsets = self._subscription.all_consumed_offsets() self._coordinator.commit_offsets_sync(offsets) def committed(self, partition): """Get the last committed offset for the given partition This offset will be used as the position for the consumer in the event of a failure. This call may block to do a remote call if the partition in question isn't assigned to this consumer or if the consumer hasn't yet initialized its cache of committed offsets. Arguments: partition (TopicPartition): the partition to check Returns: The last committed offset, or None if there was no prior commit. """ assert self.config['api_version'] >= (0, 8, 1) if self._subscription.is_assigned(partition): committed = self._subscription.assignment[partition].committed if committed is None: self._coordinator.refresh_committed_offsets_if_needed() committed = self._subscription.assignment[partition].committed else: commit_map = self._coordinator.fetch_committed_offsets([partition]) if partition in commit_map: committed = commit_map[partition].offset else: committed = None return committed def topics(self): """Get all topic metadata topics the user is authorized to view. [Not Implemented Yet] Returns: {topic: [partition_info]} """ raise NotImplementedError('TODO') def partitions_for_topic(self, topic): """Get metadata about the partitions for a given topic. Arguments: topic (str): topic to check Returns: set: partition ids """ return self._client.cluster.partitions_for_topic(topic) def poll(self, timeout_ms=0): """Fetch data from assigned topics / partitions. Records are fetched and returned in batches by topic-partition. On each poll, consumer will try to use the last consumed offset as the starting offset and fetch sequentially. The last consumed offset can be manually set through seek(partition, offset) or automatically set as the last committed offset for the subscribed list of partitions. Incompatible with iterator interface -- use one or the other, not both. Arguments: timeout_ms (int, optional): milliseconds to spend waiting in poll if data is not available. If 0, returns immediately with any records that are available now. Must not be negative. Default: 0 Returns: dict: topic to list of records since the last fetch for the subscribed list of topics and partitions """ assert timeout_ms >= 0, 'Timeout must not be negative' assert self._iterator is None, 'Incompatible with iterator interface' # poll for new data until the timeout expires start = time.time() remaining = timeout_ms while True: records = self._poll_once(remaining) if records: # before returning the fetched records, we can send off the # next round of fetches and avoid block waiting for their # responses to enable pipelining while the user is handling the # fetched records. self._fetcher.init_fetches() return records elapsed_ms = (time.time() - start) * 1000 remaining = timeout_ms - elapsed_ms if remaining <= 0: return {} def _poll_once(self, timeout_ms): """ Do one round of polling. In addition to checking for new data, this does any needed heart-beating, auto-commits, and offset updates. Arguments: timeout_ms (int): The maximum time in milliseconds to block Returns: dict: map of topic to list of records (may be empty) """ if self.config['api_version'] >= (0, 8, 2): # TODO: Sub-requests should take into account the poll timeout (KAFKA-1894) self._coordinator.ensure_coordinator_known() if self.config['api_version'] >= (0, 9): # ensure we have partitions assigned if we expect to if self._subscription.partitions_auto_assigned(): self._coordinator.ensure_active_group() # fetch positions if we have partitions we're subscribed to that we # don't know the offset for if not self._subscription.has_all_fetch_positions(): self._update_fetch_positions(self._subscription.missing_fetch_positions()) # init any new fetches (won't resend pending fetches) records = self._fetcher.fetched_records() # if data is available already, e.g. from a previous network client # poll() call to commit, then just return it immediately if records: return records self._fetcher.init_fetches() self._client.poll(timeout_ms) return self._fetcher.fetched_records() def position(self, partition): """Get the offset of the next record that will be fetched Arguments: partition (TopicPartition): partition to check """ assert self._subscription.is_assigned(partition) offset = self._subscription.assignment[partition].position if offset is None: self._update_fetch_positions(partition) offset = self._subscription.assignment[partition].position return offset def pause(self, *partitions): """Suspend fetching from the requested partitions. Future calls to poll() will not return any records from these partitions until they have been resumed using resume(). Note that this method does not affect partition subscription. In particular, it does not cause a group rebalance when automatic assignment is used. Arguments: *partitions (TopicPartition): partitions to pause """ for partition in partitions: log.debug("Pausing partition %s", partition) self._subscription.pause(partition) def resume(self, *partitions): """Resume fetching from the specified (paused) partitions. Arguments: *partitions (TopicPartition): partitions to resume """ for partition in partitions: log.debug("Resuming partition %s", partition) self._subscription.resume(partition) def seek(self, partition, offset): """Manually specify the fetch offset for a TopicPartition. Overrides the fetch offsets that the consumer will use on the next poll(). If this API is invoked for the same partition more than once, the latest offset will be used on the next poll(). Note that you may lose data if this API is arbitrarily used in the middle of consumption, to reset the fetch offsets. Arguments: partition (TopicPartition): partition for seek operation offset (int): message offset in partition """ assert offset >= 0 log.debug("Seeking to offset %s for partition %s", offset, partition) self._subscription.assignment[partition].seek(offset) def seek_to_beginning(self, *partitions): """Seek to the oldest available offset for partitions. Arguments: *partitions: optionally provide specific TopicPartitions, otherwise default to all assigned partitions """ if not partitions: partitions = self._subscription.assigned_partitions() for tp in partitions: log.debug("Seeking to beginning of partition %s", tp) self._subscription.need_offset_reset(tp, OffsetResetStrategy.EARLIEST) def seek_to_end(self, *partitions): """Seek to the most recent available offset for partitions. Arguments: *partitions: optionally provide specific TopicPartitions, otherwise default to all assigned partitions """ if not partitions: partitions = self._subscription.assigned_partitions() for tp in partitions: log.debug("Seeking to end of partition %s", tp) self._subscription.need_offset_reset(tp, OffsetResetStrategy.LATEST) def subscribe(self, topics=(), pattern=None, listener=None): """Subscribe to a list of topics, or a topic regex pattern Partitions will be dynamically assigned via a group coordinator. Topic subscriptions are not incremental: this list will replace the current assignment (if there is one). This method is incompatible with assign() Arguments: topics (list): List of topics for subscription. pattern (str): Pattern to match available topics. You must provide either topics or pattern, but not both. listener (ConsumerRebalanceListener): Optionally include listener callback, which will be called before and after each rebalance operation. As part of group management, the consumer will keep track of the list of consumers that belong to a particular group and will trigger a rebalance operation if one of the following events trigger: * Number of partitions change for any of the subscribed topics * Topic is created or deleted * An existing member of the consumer group dies * A new member is added to the consumer group When any of these events are triggered, the provided listener will be invoked first to indicate that the consumer's assignment has been revoked, and then again when the new assignment has been received. Note that this listener will immediately override any listener set in a previous call to subscribe. It is guaranteed, however, that the partitions revoked/assigned through this interface are from topics subscribed in this call. """ if not topics: self.unsubscribe() else: self._subscription.subscribe(topics=topics, pattern=pattern, listener=listener) # regex will need all topic metadata if pattern is not None: self._client.cluster.need_metadata_for_all = True log.debug("Subscribed to topic pattern: %s", topics) else: self._client.set_topics(self._subscription.group_subscription()) log.debug("Subscribed to topic(s): %s", topics) def subscription(self): """Get the current topic subscription. Returns: set: {topic, ...} """ return self._subscription.subscription def unsubscribe(self): """Unsubscribe from all topics and clear all assigned partitions.""" self._subscription.unsubscribe() self._coordinator.close() self._client.cluster.need_metadata_for_all_topics = False log.debug("Unsubscribed all topics or patterns and assigned partitions") def _update_fetch_positions(self, partitions): """ Set the fetch position to the committed position (if there is one) or reset it using the offset reset policy the user has configured. Arguments: partitions (List[TopicPartition]): The partitions that need updating fetch positions Raises: NoOffsetForPartitionError: If no offset is stored for a given partition and no offset reset policy is defined """ if self.config['api_version'] >= (0, 8, 1): # refresh commits for all assigned partitions self._coordinator.refresh_committed_offsets_if_needed() # then do any offset lookups in case some positions are not known self._fetcher.update_fetch_positions(partitions) def _message_generator(self): while time.time() < self._consumer_timeout: if self.config['api_version'] >= (0, 8, 2): self._coordinator.ensure_coordinator_known() if self.config['api_version'] >= (0, 9): # ensure we have partitions assigned if we expect to if self._subscription.partitions_auto_assigned(): self._coordinator.ensure_active_group() # fetch positions if we have partitions we're subscribed to that we # don't know the offset for if not self._subscription.has_all_fetch_positions(): partitions = self._subscription.missing_fetch_positions() self._update_fetch_positions(partitions) # init any new fetches (won't resend pending fetches) self._fetcher.init_fetches() self._client.poll( max(0, self._consumer_timeout - time.time()) * 1000) timeout_at = min(self._consumer_timeout, self._client._delayed_tasks.next_at() + time.time(), self._client.cluster.ttl() / 1000.0 + time.time()) if time.time() > timeout_at: continue for msg in self._fetcher: yield msg if time.time() > timeout_at: break def __iter__(self): # pylint: disable=non-iterator-returned return self def __next__(self): if not self._iterator: self._iterator = self._message_generator() # consumer_timeout_ms can be used to stop iteration early if self.config['consumer_timeout_ms'] >= 0: self._consumer_timeout = time.time() + ( self.config['consumer_timeout_ms'] / 1000.0) try: return next(self._iterator) except StopIteration: self._iterator = None raise # old KafkaConsumer methods are deprecated def configure(self, **configs): raise NotImplementedError( 'deprecated -- initialize a new consumer') def set_topic_partitions(self, *topics): raise NotImplementedError( 'deprecated -- use subscribe() or assign()') def fetch_messages(self): raise NotImplementedError( 'deprecated -- use poll() or iterator interface') def get_partition_offsets(self, topic, partition, request_time_ms, max_num_offsets): raise NotImplementedError( 'deprecated -- send an OffsetRequest with KafkaClient') def offsets(self, group=None): raise NotImplementedError('deprecated -- use committed(partition)') def task_done(self, message): raise NotImplementedError( 'deprecated -- commit offsets manually if needed')