Change history for Faust 1.7

This document contain change notes for bugfix releases in the Faust 1.7.x series. If you’re looking for changes in the latest series, please visit the latest Changes.

For even older releases you can visit the History section.



2019-07-12 1:13 P.M PST


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  • Tables: Fix for Issue #383 when using the Cython extension.



2019-07-12 12:00 P.M PST


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  • Tables: Fixed memory leak/back pressure in changelog producer buffer (Issue #383)

  • Models: Do not attempt to parse datetime when coerce/isodates disabled.

    Version 1.7 introduced a regression where datetimes were attempted to be parsed as ISO-8601 even with the isodates setting disabled.

    A regression test was added for this bug.

  • Models: New date_parser option to change datetime parsing function.

    The default date parser supports ISO-8601 only. To support this format and many other formats (such as 'Sat Jan 12 00:44:36 +0000 2019') you can select to use python-dateutil as the parser.

    To change the date parsing function for a model globally:

    from dateutil.parser import parse as parse_date
    class Account(faust.Record, coerce=True, date_parser=parse_date):
        date_joined: datetime

    To change the date parsing function for a specific field:

    from dateutil.parser import parse as parse_date
    from faust.models.fields import DatetimeField
    class Account(faust.Record, coerce=True):
        # date_joined: supports ISO-8601 only (default)
        date_joined: datetime
        #: date_last_login: comes from weird system with more human
        #: readable dates ('Sat Jan 12 00:44:36 +0000 2019').
        #: The dateutil parser can handle many different date and time
        #: formats.
        date_last_login: datetime = DatetimeField(date_parser=parse_date)
  • Models: Adds FieldDescriptor.exclude to exclude field when serialized

    See Excluding fields from representation for more information.

  • Documentation: improvements by…



2019-07-09 2:36 P.M PST


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  • Stream: Exactly once processing now include the app id in transactional ids.

    This was done to support running multiple apps on the same Kafka broker.

    Contributed by Cesar Pantoja (@CesarPantoja).

  • Web: Fixed bug where sensor index should display when debug is enabled


    If you want to enable the sensor statistics endpoint in production, without enabling the debug setting, you can do so by adding the following code:

    app.web.blueprints.add('/stats/', 'faust.web.apps.stats:blueprint')

    Contributed by @tyong920

  • Transport: The default value for broker_request_timeout is now 90 seconds (Issue #259)

  • Transport: Raise error if broker_session_timeout is greater than broker_request_timeout (Closes #259)

  • Dependencies: Now supports click 7.0 and later.

  • Dependencies: faust[debug] now depends on aiomonitor 0.4.4 or later.

  • Models: Field defined as Optional[datetime] now works with coerce and isodates settings.

    Previously a model would not recognize:

    class X(faust.Record, coerce=True):
        date: Optional[datetime]
    as a :class:`~faust.models.fields.DatetimeField` and when
    deserializing the field would end up as a string.
    It's now properly converted to :class:`~datetime.datetime`.
  • RocksDB: Adds table_key_index_size setting (Closes #372)

  • RocksDB: Reraise original error if python-rocksdb cannot be imported.

    Thanks to Sohaib Farooqi.

  • Django: Autodiscovery support now waits for Django to be fully setup.

    Contributed by Tomasz Nguyen (@swist).

  • Documentation improvements by:



2019-06-06 6:00 P.M PST


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Backward Incompatible Changes

  • Transports: The in-memory transport has been removed (Issue #295).

    This transport was experimental and not working properly, so to avoid confusion we have removed it completely.

  • Stream: The Message.stream_meta attribute has been removed.

    This was used to keep arbitrary state for sensors during processing of a message.

    If you by rare chance are relying on this attribute to exist, you must now initialize it before using it:

    stream_meta = getattr(event.message, 'stream_meta', None)
    if stream_meta is None:
        stream_meta = event.message.stream_meta = {}


  • Requirements

  • Documentation: Documented a new deployment strategy to minimize rebalancing issues.

    See Managing a cluster for more information.

  • Models: Implements model validation.

    Validation of fields can be enabled by using the validation=True class option:

    import faust
    from decimal import Decimal
    class X(faust.Record, validation=True):
        name: str
        amount: Decimal

    When validation is enabled, the model will validate that the fields values are of the correct type.

    Fields can now also have advanced validation options, and you enable these by writing explicit field descriptors:

    import faust
    from decimal import Decimal
    from faust.models.fields import DecimalField, StringField
    class X(faust.Record, validation=True):
        name: str = StringField(max_length=30)
        amount: Decimal = DecimalField(min_value=10.0, max_value=1000.0)

    If you want to run validation manually, you can do so by keeping validation=False on the class, but calling model.is_valid():

    if not model.is_valid():
  • Models: Implements generic coercion support.

    This new feature replaces the isodates=True/decimals=True options and can be enabled by passing coerce=True:

    class Account(faust.Record, coerce=True):
        name: str
        login_times: List[datetime]
  • Testing: New experimental livecheck production testing API.

    There is no documentation yet, but an example in examples//

    This is a new API to do end-to-end testing directly in production.

  • Topic: Adds new topic.send_soon() non-async method to buffer messages.

    This method can be used by any non-async def function to buffer up messages to be produced.

    It returns Awaitable[RecordMetadata]: a promise evaluated once the message is actually sent.

  • Stream: New Stream.filter method added useful for filtering events before repartitioning a stream.

  • App: New broker_consumer/broker_producer settings.

    These can now be used to configure individual transports for consuming and producing.

    The default value for both settings are taken from the broker setting.

    For example you can use aiokafka for the consumer, and confluent_kafka for the producer:

    app = faust.App(
  • App: New broker_max_poll_interval setting.

    Contributed by Miha Troha (@mihatroha).

  • App: New topic_disable_leader setting disables the leader topic.

  • Table: Table constructor now accepts options argument passed on to underlying RocksDB storage.

    This can be used to configure advanced RocksDB options, such as block size, cache size, etc.

    Contributed by Miha Troha (@mihatroha).


  • Stream: Fixes bug where non-finished event is acked (Issue #355).

  • Producer: Exactly once: Support producing to non-transactional topics (Issue #339)

  • Agent: Test: Fixed asyncio.CancelledError (Issue #322).

  • Cython: Fixed issue with sensor state not being passed to after.

  • Tables: Key index: now inherits configuration from source table (Issue #325)

  • App: Fix list of strings for broker param in URL (Issue #330).

    Contributed by Nimish Telang (@nimish).

  • Table: Fixed blocking behavior when populating tables.

    Symptom was warnings about timers waking up too late.

  • Documentation Fixes by:


  • Documentation: Rewrote fragmented documentation to be more concise.

  • Documentation improvements by