faust.transport.consumer

Consumer

The Consumer is responsible for:

  • Holds reference to the transport that created it

  • … and the app via self.transport.app.

  • Has a callback that usually points back to Conductor.on_message.

  • Receives messages and calls the callback for every message received.

  • Keeps track of the message and its acked/unacked status.

  • The Conductor forwards the message to all Streams that subscribes to the topic the message was sent to.

    • Messages are reference counted, and the Conductor increases the reference count to the number of subscribed streams.
    • Stream.__aiter__ is set up in a way such that when what is iterating over the stream is finished with the message, a finally: block will decrease the reference count by one.
    • When the reference count for a message hits zero, the stream will call Consumer.ack(message), which will mark that tp+offset combination as “commitable”
    • If all the streams share the same key_type/value_type, the conductor will only deserialize the payload once.
  • Commits the offset at an interval

    • The Consumer has a background thread that periodically commits the offset.
    • If the consumer marked an offset as committable this thread will advance the comitted offset.
    • To find the offset that it can safely advance to the commit thread will traverse the _acked mapping of TP to list of acked offsets, by finding a range of consecutive acked offsets (see note in _new_offset).
class faust.transport.consumer.Fetcher(app: faust.types.app.AppT, **kwargs) → None[source]
logger = <Logger faust.transport.consumer (WARNING)>
coroutine on_stop(self) → None[source]

Called every time before the service is stopped/restarted.

Return type:None
class faust.transport.consumer.Consumer(transport: faust.types.transports.TransportT, callback: Callable[faust.types.tuples.Message, Awaitable], on_partitions_revoked: Callable[Set[faust.types.tuples.TP], Awaitable[None]], on_partitions_assigned: Callable[Set[faust.types.tuples.TP], Awaitable[None]], *, commit_interval: float = None, commit_livelock_soft_timeout: float = None, loop: asyncio.events.AbstractEventLoop = None, **kwargs) → None[source]

Base Consumer.

logger = <Logger faust.transport.consumer (WARNING)>
class TopicBuffer → None
add(tp: faust.types.tuples.TP, buffer: List) → None
Return type:None
classmethod map_from_records(records: Mapping[faust.types.tuples.TP, List]) → MutableMapping[str, faust.transport.utils.TopicBuffer]
Return type:MutableMapping[str, TopicBuffer[]]
consumer_stopped_errors = ()

Tuple of exception types that may be raised when the underlying consumer driver is stopped.

flow_active = True
on_init_dependencies() → Iterable[mode.types.services.ServiceT][source]

Callback to be used to add service dependencies.

Return type:Iterable[ServiceT[]]
stop_flow() → None[source]
Return type:None
resume_flow() → None[source]
Return type:None
pause_partitions(tps: Iterable[faust.types.tuples.TP]) → None[source]
Return type:None
resume_partitions(tps: Iterable[faust.types.tuples.TP]) → None[source]
Return type:None
track_message(message: faust.types.tuples.Message) → None[source]
Return type:None
ack(message: faust.types.tuples.Message) → bool[source]
Return type:bool
getmany(timeout: float) → AsyncIterator[Tuple[faust.types.tuples.TP, faust.types.tuples.Message]][source]
Return type:AsyncIterator[Tuple[TP, Message]]
coroutine commit(self, topics: AbstractSet[Union[str, faust.types.tuples.TP]] = None, start_new_transaction: bool = True) → bool[source]

Maybe commit the offset for all or specific topics.

Parameters:topics (Optional[AbstractSet[Union[str, TP]]]) – Set containing topics and/or TopicPartitions to commit.
Return type:bool
coroutine commit_and_end_transactions(self) → None[source]
Return type:None
coroutine force_commit(self, topics: AbstractSet[Union[str, faust.types.tuples.TP]] = None, start_new_transaction: bool = True) → bool[source]
Return type:bool
coroutine maybe_wait_for_commit_to_finish(self) → bool[source]
Return type:bool
coroutine on_partitions_assigned(self, assigned: Set[faust.types.tuples.TP]) → None[source]
Return type:None
coroutine on_partitions_revoked(self, revoked: Set[faust.types.tuples.TP]) → None[source]
Return type:None
coroutine on_restart(self) → None[source]

Called every time when the service is restarted.

Return type:None
coroutine on_stop(self) → None[source]

Called every time before the service is stopped/restarted.

Return type:None
coroutine on_task_error(self, exc: BaseException) → None[source]
Return type:None
coroutine perform_seek(self) → None[source]
Return type:None
coroutine seek(self, partition: faust.types.tuples.TP, offset: int) → None[source]
Return type:None
coroutine seek_to_committed(self) → Mapping[faust.types.tuples.TP, int][source]
Return type:Mapping[TP, int]
coroutine wait_empty(self) → None[source]

Wait for all messages that started processing to be acked.

Return type:None
close() → None[source]
Return type:None
unacked
Return type:Set[Message]