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AMQP (RabbitMQ)

AMQP via RabbitMQ is the production default for distributed deployments. Mature, widely deployed, with excellent tooling.

Why AMQP​

StrengthBenefit
Mature15+ years of production use
Durable queuesMessages survive broker restarts
Flexible routingTopic exchanges, headers, fanout
Management UIBuilt-in web console
Dead letter queuesAutomatic failure handling

Configuration​

[bus]
backend = "amqp"

[bus.amqp]
url = "amqp://guest:guest@localhost:5672"
exchange = "angzarr.events"
prefetch_count = 10

Environment Variables​

export AMQP_URL="amqp://guest:guest@localhost:5672"
export BUS_BACKEND="amqp"

Exchange Topology​

Angzarr creates a topic exchange for event routing:

Exchange: angzarr.events (topic)
    │
    ├── Binding: player.# → queue: player-projector
    ├── Binding: player.# → queue: output-projector
    ├── Binding: hand.# → queue: hand-saga
    └── Binding: *.# → queue: topology-tracker

Routing Keys​

Events are published with routing keys: {domain}.{event_type}

player.PlayerRegistered
player.FundsDeposited
hand.CardsDealt
hand.HandComplete

Queue Configuration​

Each handler gets a dedicated queue with configurable durability:

# Handler queue settings
queues:
  player-projector:
    durable: true
    auto_delete: false
    exclusive: false
    arguments:
      x-dead-letter-exchange: angzarr.dlx

Dead Letter Handling​

Failed messages route to a dead letter exchange:

angzarr.dlx (fanout)
    │
    └── angzarr.dlq (queue)

Monitor the DLQ for processing failures:

# Check DLQ depth
rabbitmqctl list_queues name messages | grep dlq

Helm Deployment​

# values.yaml
bus:
  backend: amqp

amqp:
  enabled: true
  host: rabbitmq.messaging.svc.cluster.local
  port: 5672
  credentials:
    secretName: rabbitmq-credentials
    usernameKey: username
    passwordKey: password

Testing​

# Run AMQP tests (requires testcontainers)
cargo test --test bus_amqp --features amqp

# Requires podman socket
systemctl --user start podman.socket

Management Console​

RabbitMQ includes a web management interface:

http://localhost:15672
Default credentials: guest/guest

Monitor:

  • Queue depths
  • Message rates
  • Consumer connections
  • Exchange bindings

When to Use AMQP​

  • Production default — Most deployments
  • Existing RabbitMQ — Already in infrastructure
  • Complex routing — Headers, topics, fanout
  • Operational maturity — Team familiarity

Next Steps​