Cross-process IPC bridge

The memory endpoint is more than an in-process channel: its url (alias topic) is a transport URL, so the same endpoint can bridge separate processes on one machine over a Unix socket or Windows named pipe — no broker required.

Transport URLs

The url field selects the transport:

The consumer side binds/listens and must be started before the publisher connects. IPC does not support subscribe_mode or request_reply. enable_nack defaults to true, but redelivery is consumer-local: a nacked message is retried inside the consumer and is lost if the consumer process dies.

Example: ingest process → Kafka

One process reads from a Unix socket and forwards to Kafka. Start this consumer first so the socket exists before any producer connects:

ipc_ingest:
  input:
    memory:
      url: "ipc://orders"
      capacity: 256
  output:
    kafka:
      topic: "orders"
      url: "localhost:9092"

mq-bridge-app --config ipc_ingest.yaml

The named form is used rather than an explicit path so no privileged directory has to exist up front: /run/mq-bridge/ needs root, and ipc://orders falls back to $XDG_RUNTIME_DIR/mq-bridge or /tmp/mq-bridge. Give an absolute ipc:///abs/path.sock only once you have created and permissioned that directory.

Any other process on the same host can now publish into ipc://orders — via its own mq-bridge route, or programmatically through a Publisher built on a memory endpoint (see the embedding tutorial) — and the messages flow through to Kafka.

When to use it

• Decouple a producer and a sink into separate processes without standing up a broker — e.g. an app writes to the socket, a long-lived bridge process owns the Kafka/DB connections and batching.
• Language boundary. A Python or Node process publishes into the socket; a Rust bridge process does the heavy I/O.

capacity bounds the in-flight channel; tune it alongside the guidance in Performance tuning.

See also

• Configuration grammar — this is Route 9 of the annotated example, with the full URL grammar in comments.
• Endpoints (concepts).