Configuration

Create a BabelQueue runtime and point it at your broker with a URL. The transport is chosen from the URL scheme — no separate “broker” flag.

Broker URL

from babelqueue import BabelQueue

# Redis (extra: babelqueue[redis])
app = BabelQueue("redis://localhost:6379/0", queue="orders")

# RabbitMQ (extra: babelqueue[amqp])
# app = BabelQueue("amqp://guest:guest@localhost:5672/", queue="orders")

# Amazon SQS (extra: babelqueue[sqs])
# app = BabelQueue("sqs://eu-central-1", queue="orders")

# Azure Service Bus (extra: babelqueue[azureservicebus])
# app = BabelQueue("sb://<namespace>.servicebus.windows.net", queue="orders")

# Apache Pulsar (extra: babelqueue[pulsar])
# app = BabelQueue("pulsar://localhost:6650", queue="orders")

# Apache Kafka (extra: babelqueue[kafka])
# app = BabelQueue("kafka://localhost:9092", queue="orders")

# Apache ActiveMQ Artemis (extra: babelqueue[artemis])
# app = BabelQueue("artemis://localhost:5672", queue="orders")

# In-process, great for tests/local — no broker required
# app = BabelQueue("memory://", queue="orders")

The sqs:// URL is sqs://<region> with optional query params: endpoint (LocalStack/ElasticMQ), prefix (a queue-URL prefix that skips GetQueueUrl), fifo=1, group_id, wait_time. The transport sends the canonical envelope with the §3 MessageAttributes and reconciles attempts to ApproximateReceiveCount − 1.

The sb:// URL is sb://<namespace>.servicebus.windows.net and authenticates with DefaultAzureCredential (Azure AD); pass connection_string=... to AsbTransport for SAS auth, or BabelQueue(transport=...) with a built client. It maps the envelope onto native Service Bus fields (§4) and reconciles attempts to max(body, DeliveryCount − 1).

The pulsar:// URL is pulsar://<host>:<port> (or pulsar+ssl://); pass a built client via BabelQueue(transport=...) for TLS/token auth. It projects the envelope onto native Pulsar message properties (bq-job = URN, plus the bq- fields, §5), defaults to a Shared subscription named babelqueue, and reconciles attempts to max(body, redelivery_count) — the redelivery count is 0-based, so no −1.

The kafka:// URL is kafka://<host>:<port>[,<host>:<port>]; pass an injected producer + consumer_factory for custom auth. The record value is the envelope, projected onto bq- headers (§6); consume is process-then-commit (enable.auto.commit=false) and attempts reconciles to the authoritative bq-attempts header (else the body). Kafka has no native delay/DLQ, so the runtime owns retry by republishing with attempts+1 and dead-letters to <queue>.dlq.

The artemis:// URL is artemis://<host>:<port> (or artemis+ssl://) — Apache ActiveMQ Artemis over AMQP 1.0 (python-qpid-proton, not RabbitMQ’s 0-9-1 pika); pass a built connection via BabelQueue(transport=...) for auth/TLS. It projects the envelope onto the AMQP a JMS peer reads — x-opt-jms-type = URN, correlation-id = trace_id, plus the string bq_ application properties (underscored — JMS property names must be valid Java identifiers; §7) — and reconciles attempts to max(body, delivery_count); the AMQP delivery-count is 0-based, so no −1.

Options

app = BabelQueue(
    "redis://localhost:6379/0",
    queue="orders",
    max_attempts=3,
    dead_letter=True,
    on_unknown_urn="dead_letter",
)

Need just the wire codec, with no broker wiring? Import EnvelopeCodec directly — see Producing messages.

Next: Producing messages.