Python SDK reference.

Synapse - transport adapters

A Synapse is the message bus. The application picks a backend, passes the adapter to the Dendrite, and never touches the wire format again. All adapters subclass the same abstract Synapse base.

class Synapse(ABC):
    async def connect(self) -> None: ...
    async def close(self)   -> None: ...

    async def publish(self, subject: str, signal: Signal) -> None: ...

    async def subscribe(
        self,
        subject:    str,
        handler:    Callable[[Signal], Awaitable[None]],
        *,
        queue_group: str | None = None,
    ) -> Subscription: ...

    async def request(
        self,
        subject: str,
        signal:  Signal,
        *,
        timeout_s: float = 5.0,
    ) -> Signal: ...

Bundled adapters

URL factory

from cosmonapse import synapse_from_url, connect_synapse, MemorySynapse

# Build (does not connect):
syn = synapse_from_url("cosmo://localhost:7070")    # DevSynapse
syn = synapse_from_url("nats://nats:4222")            # NatsSynapse
syn = synapse_from_url("kafka://broker:9092")         # KafkaSynapse

# memory:// has no URL  -  it is process-local, so build it directly:
syn = MemorySynapse()

# Build + connect in one call:
syn = await connect_synapse("cosmo://127.0.0.1:7070")

Subjects

Subjects follow cosmonapse.<namespace>.<TYPE>. Queue groups load-balance within a group; subscribers with no queue_group form the Doppler population (every matching message goes to each one). Application code must never construct subjects directly - let the Dendrite resolve them.