Skip to content

⚙️ Backend-Specific Event Settings

Events often need fine-grained control over how they’re published—things like partitioning, headers, priorities, timestamps, etc. Dispytch supports this via the optional __backend_config__ class attribute on any EventBase subclass.

This lets you define backend-specific settings inside your event instance in a clean, declarative way.

🧩 What Is __backend_config__?

__backend_config__ is an optional BaseModel that lets you pass custom options to your producer. Each backend (Kafka, RabbitMQ, Redis, etc.) can define its own config schema.

🔎 Example

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
class UserCreated(EventBase):
    __topic__ = "user_events"
    __event_type__ = "user_created"

    user: User
    timestamp: int


async def example_emit(emitter: EventEmitter, user: User):
    await emitter.emit(
        UserCreated(
            user=user,
            timestamp=int(datetime.now().timestamp()),
            __backend_config__=KafkaEventConfig(
                partition_key=user.id,
            )
        )

    )

🪵 KafkaEventConfig

Use this config to control how events are sent to Kafka.

1
2
3
4
5
class KafkaEventConfig(BaseModel):
    partition_key: Optional[Any] = None
    partition: Optional[int] = None
    timestamp_ms: Optional[int] = None
    headers: Optional[dict] = None

🐇 RabbitMQEventConfig

RabbitMQ gives you full control over message delivery via its rich AMQP options.

1
2
3
4
5
6
7
class RabbitMQEventConfig(BaseModel):
    delivery_mode: int | None = None
    priority: int | None = None
    expiration: int | datetime | float | timedelta | None = None
    headers: dict | None = None
    content_type: str | None = None
    ...

Using this config, you can set AMQP-specific things

🔨 Implementing Custom Configs

If you're writing a custom producer (see Writing Custom Producers & Consumers), you can define your own config schema:

1
2
3
class MyCustomConfig(BaseModel):
    foo: str
    retries: int = 3

Then inspect and apply it inside your send() method:

1
2
if isinstance(config, MyCustomConfig):
    do_something_with(config.foo)