stack-kafka-python

Kafka Python client

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Python client for the Apache Kafka distributed stream processing system. kafka-python is designed to function much like the official java client, with a sprinkling of pythonic interfaces (e.g., consumer iterators).

kafka-python is best used with newer brokers (0.9+), but is backwards-compatible with older versions (to 0.8.0). Some features will only be enabled on newer brokers. For example, fully coordinated consumer groups -- i.e., dynamic partition assignment to multiple consumers in the same group -- requires use of 0.9+ kafka brokers. Supporting this feature for earlier broker releases would require writing and maintaining custom leadership election and membership / health check code (perhaps using zookeeper or consul). For older brokers, you can achieve something similar by manually assigning different partitions to each consumer instance with config management tools like chef, ansible, etc. This approach will work fine, though it does not support rebalancing on failures. See https://kafka-python.readthedocs.io/en/master/compatibility.html for more details.

Please note that the master branch may contain unreleased features. For release documentation, please see readthedocs and/or python's inline help.

pip install kafka-python

KafkaConsumer

KafkaConsumer is a high-level message consumer, intended to operate as similarly as possible to the official java client. Full support for coordinated consumer groups requires use of kafka brokers that support the Group APIs: kafka v0.9+.

See https://kafka-python.readthedocs.io/en/master/apidoc/KafkaConsumer.html for API and configuration details.

The consumer iterator returns ConsumerRecords, which are simple namedtuples that expose basic message attributes: topic, partition, offset, key, and value:

from kafka import KafkaConsumer consumer = KafkaConsumer('my_favorite_topic') for msg in consumer: ... print (msg)

join a consumer group for dynamic partition assignment and offset commits

from kafka import KafkaConsumer consumer = KafkaConsumer('my_favorite_topic', group_id='my_favorite_group') for msg in consumer: ... print (msg)

manually assign the partition list for the consumer

from kafka import TopicPartition consumer = KafkaConsumer(bootstrap_servers='localhost:1234') consumer.assign([TopicPartition('foobar', 2)]) msg = next(consumer)

Deserialize msgpack-encoded values

consumer = KafkaConsumer(value_deserializer=msgpack.loads) consumer.subscribe(['msgpackfoo']) for msg in consumer: ... assert isinstance(msg.value, dict)

Access record headers. The returned value is a list of tuples

with str, bytes for key and value

for msg in consumer: ... print (msg.headers)

Get consumer metrics

metrics = consumer.metrics()

KafkaProducer

KafkaProducer is a high-level, asynchronous message producer. The class is intended to operate as similarly as possible to the official java client. See https://kafka-python.readthedocs.io/en/master/apidoc/KafkaProducer.html for more details.

from kafka import KafkaProducer producer = KafkaProducer(bootstrap_servers='localhost:1234') for _ in range(100): ... producer.send('foobar', b'some_message_bytes')

Block until a single message is sent (or timeout)

future = producer.send('foobar', b'another_message') result = future.get(timeout=60)

Block until all pending messages are at least put on the network

NOTE: This does not guarantee delivery or success! It is really

only useful if you configure internal batching using linger_ms

producer.flush()

Use a key for hashed-partitioning

producer.send('foobar', key=b'foo', value=b'bar')

Serialize json messages

import json producer = KafkaProducer(value_serializer=lambda v: json.dumps(v).encode('utf-8')) producer.send('fizzbuzz', {'foo': 'bar'})

Serialize string keys

producer = KafkaProducer(key_serializer=str.encode) producer.send('flipflap', key='ping', value=b'1234')

Compress messages

producer = KafkaProducer(compression_type='gzip') for i in range(1000): ... producer.send('foobar', b'msg %d' % i)

Include record headers. The format is list of tuples with string key

and bytes value.

producer.send('foobar', value=b'c29tZSB2YWx1ZQ==', headers=[('content-encoding', b'base64')])

Get producer performance metrics

metrics = producer.metrics()

Thread safety

The KafkaProducer can be used across threads without issue, unlike the KafkaConsumer which cannot.

While it is possible to use the KafkaConsumer in a thread-local manner, multiprocessing is recommended.

Compression

kafka-python supports gzip compression/decompression natively. To produce or consume lz4 compressed messages, you should install python-lz4 (pip install lz4). To enable snappy compression/decompression install python-snappy (also requires snappy library). See https://kafka-python.readthedocs.io/en/master/install.html#optional-snappy-install for more information.

Protocol

A secondary goal of kafka-python is to provide an easy-to-use protocol layer for interacting with kafka brokers via the python repl. This is useful for testing, probing, and general experimentation. The protocol support is leveraged to enable a KafkaClient.check_version() method that probes a kafka broker and attempts to identify which version it is running (0.8.0 to 1.1+).

Low-level

Legacy support is maintained for low-level consumer and producer classes, SimpleConsumer and SimpleProducer. See https://kafka-python.readthedocs.io/en/master/simple.html?highlight=SimpleProducer for API details.