RabbitMQ

Detailed documentation on the RabbitMQ pubsub component

Component format

To set up RabbitMQ pub/sub, create a component of type pubsub.rabbitmq. See the pub/sub broker component file to learn how ConsumerID is automatically generated. Read the How-to: Publish and Subscribe guide on how to create and apply a pub/sub configuration.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: rabbitmq-pubsub
spec:
  type: pubsub.rabbitmq
  version: v1
  metadata:
  - name: connectionString
    value: "amqp://localhost:5672"
  - name: protocol
    value: amqp  
  - name: hostname
    value: localhost 
  - name: username
    value: username
  - name: password
    value: password  
  - name: consumerID
    value: myapp
  - name: durable
    value: false
  - name: deletedWhenUnused
    value: false
  - name: autoAck
    value: false
  - name: deliveryMode
    value: 0
  - name: requeueInFailure
    value: false
  - name: prefetchCount
    value: 0
  - name: reconnectWait
    value: 0
  - name: concurrencyMode
    value: parallel
  - name: publisherConfirm
    value: false
  - name: enableDeadLetter # Optional enable dead Letter or not
    value: true
  - name: maxLen # Optional max message count in a queue
    value: 3000
  - name: maxLenBytes # Optional maximum length in bytes of a queue.
    value: 10485760
  - name: exchangeKind
    value: fanout
  - name: saslExternal
    value: false
  - name: ttlInSeconds
    value: 60
  - name: clientName
    value: {podName}
  - name: heartBeat
    value: 10s

Warning

The above example uses secrets as plain strings. It is recommended to use a secret store for the secrets as described here.

Spec metadata fields

Communication using TLS

To configure communication using TLS, ensure that the RabbitMQ nodes have TLS enabled and provide the caCert, clientCert, clientKey metadata in the component configuration. 例如：

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: rabbitmq-pubsub
spec:
  type: pubsub.rabbitmq
  version: v1
  metadata:
  - name: host
    value: "amqps://localhost:5671"
  - name: consumerID
    value: myapp
  - name: durable
    value: false
  - name: deletedWhenUnused
    value: false
  - name: autoAck
    value: false
  - name: deliveryMode
    value: 0
  - name: requeueInFailure
    value: false
  - name: prefetchCount
    value: 0
  - name: reconnectWait
    value: 0
  - name: concurrencyMode
    value: parallel
  - name: publisherConfirm
    value: false
  - name: enableDeadLetter # Optional enable dead Letter or not
    value: true
  - name: maxLen # Optional max message count in a queue
    value: 3000
  - name: maxLenBytes # Optional maximum length in bytes of a queue.
    value: 10485760
  - name: exchangeKind
    value: fanout
  - name: saslExternal
    value: false
  - name: caCert
    value: ${{ myLoadedCACert }}
  - name: clientCert
    value: ${{ myLoadedClientCert }}
  - name: clientKey
    secretKeyRef:
      name: myRabbitMQClientKey
      key: myRabbitMQClientKey

Note that while the caCert and clientCert values may not be secrets, they can be referenced from a Dapr secret store as well for convenience.

Enabling message delivery retries

The RabbitMQ pub/sub component has no built-in support for retry strategies. This means that the sidecar sends a message to the service only once. When the service returns a result, the message will be marked as consumed regardless of whether it was processed correctly or not. Note that this is common among all Dapr PubSub components and not just RabbitMQ. Dapr can try redelivering a message a second time, when autoAck is set to false and requeueInFailure is set to true.

To make Dapr use more sophisticated retry policies, you can apply a retry resiliency policy to the RabbitMQ pub/sub component.

There is a crucial difference between the two ways to retry messages:

1. When using autoAck = false and requeueInFailure = true, RabbitMQ is the one responsible for re-delivering messages and any subscriber can get the redelivered message. If you have more than one instance of your consumer, then it’s possible that another consumer will get it. This is usually the better approach because if there’s a transient failure, it’s more likely that a different worker will be in a better position to successfully process the message.
2. Using Resiliency makes the same Dapr sidecar retry redelivering the messages. So it will be the same Dapr sidecar and the same app receiving the same message.

Create a RabbitMQ server

• Self-Hosted
• Kubernetes

You can run a RabbitMQ server locally using Docker:

docker run -d --hostname my-rabbit --name some-rabbit rabbitmq:3

You can then interact with the server using the client port: localhost:5672.

The easiest way to install RabbitMQ on Kubernetes is by using the Helm chart:

helm install rabbitmq stable/rabbitmq

Look at the chart output and get the username and password.

This will install RabbitMQ into the default namespace. To interact with RabbitMQ, find the service with: kubectl get svc rabbitmq.

For example, if installing using the example above, the RabbitMQ server client address would be:

rabbitmq.default.svc.cluster.local:5672

Use topic exchange to route messages

Setting exchangeKind to "topic" uses the topic exchanges, which are commonly used for the multicast routing of messages. Messages with a routing key will be routed to one or many queues based on the routing key defined in the metadata when subscribing. The routing key is defined by the routingKey metadata. For example, if an app is configured with a routing key keyA:

apiVersion: dapr.io/v2alpha1
kind: Subscription
metadata:
  name: orderspubsub
spec:
  topic: B
  routes: 
    default: /B
  pubsubname: pubsub
  metadata:
    routingKey: keyA

It will receive messages with routing key keyA, and messages with other routing keys are not received.

// publish messages with routing key `keyA`, and these will be received by the above example.
client.PublishEvent(context.Background(), "pubsub", "B", []byte("this is a message"), dapr.PublishEventWithMetadata(map[string]string{"routingKey": "keyA"}))
// publish messages with routing key `keyB`, and these will not be received by the above example.
client.PublishEvent(context.Background(), "pubsub", "B", []byte("this is another message"), dapr.PublishEventWithMetadata(map[string]string{"routingKey": "keyB"}))

Bind multiple routingKey

Multiple routing keys can be separated by commas.
The example below binds three routingKey: keyA, keyB, and "". Note the binding method of empty keys.

apiVersion: dapr.io/v2alpha1
kind: Subscription
metadata:
  name: orderspubsub
spec:
  topic: B
  routes: 
    default: /B
  pubsubname: pubsub
  metadata:
    routingKey: keyA,keyB,

For more information see rabbitmq exchanges.

Use priority queues

Dapr supports RabbitMQ priority queues. To set a priority for a queue, use the maxPriority topic subscription metadata.

Declarative priority queue example

apiVersion: dapr.io/v2alpha1
kind: Subscription
metadata:
  name: pubsub
spec:
  topic: checkout
  routes: 
    default: /orders
  pubsubname: order-pub-sub
  metadata:
    maxPriority: 3

Programmatic priority queue example

• Python
• JavaScript
• Go

@app.route('/dapr/subscribe', methods=['GET'])
def subscribe():
    subscriptions = [
      {
        'pubsubname': 'pubsub',
        'topic': 'checkout',
        'routes': {
          'default': '/orders'
        },
        'metadata': {'maxPriority': '3'}
      }
    ]
    return jsonify(subscriptions)

const express = require('express')
const bodyParser = require('body-parser')
const app = express()
app.use(bodyParser.json({ type: 'application/*+json' }));
const port = 3000
app.get('/dapr/subscribe', (req, res) => {
  res.json([
    {
      pubsubname: "pubsub",
      topic: "checkout",
      routes: {
        default: '/orders'
      },
      metadata: {
        maxPriority: '3'
      }
    }
  ]);
})

package main
    "encoding/json"
    "net/http"
const appPort = 3000
type subscription struct {
    PubsubName string            `json:"pubsubname"`
    Topic      string            `json:"topic"`
    Metadata   map[string]string `json:"metadata,omitempty"`
    Routes     routes            `json:"routes"`
}
type routes struct {
    Rules   []rule `json:"rules,omitempty"`
    Default string `json:"default,omitempty"`
}
// This handles /dapr/subscribe
func configureSubscribeHandler(w http.ResponseWriter, _ *http.Request) {
    t := []subscription{
        {
            PubsubName: "pubsub",
            Topic:      "checkout",
            Routes: routes{
                Default: "/orders",
            },
      Metadata: map[string]string{
        "maxPriority": "3"
      },
        },
    }
    w.WriteHeader(http.StatusOK)
    json.NewEncoder(w).Encode(t)
}

Setting a priority when publishing a message

To set a priority on a message, add the publish metadata key maxPriority to the publish endpoint or SDK method.

• HTTP API (Bash)
• Python
• JavaScript
• Go

curl -X POST http://localhost:3601/v1.0/publish/order-pub-sub/orders?metadata.priority=3 -H "Content-Type: application/json" -d '{"orderId": "100"}'

with DaprClient() as client:
        result = client.publish_event(
            pubsub_name=PUBSUB_NAME,
            topic_name=TOPIC_NAME,
            data=json.dumps(orderId),
            data_content_type='application/json',
            metadata= { 'priority': '3' })

await client.pubsub.publish(PUBSUB_NAME, TOPIC_NAME, orderId, { 'priority': '3' });

client.PublishEvent(ctx, PUBSUB_NAME, TOPIC_NAME, []byte(strconv.Itoa(orderId)), map[string]string{"priority": "3"})

Use quorum queues

By default, Dapr creates classic queues. To create quorum queues, add the following metadata to your pub/sub subscription

apiVersion: dapr.io/v2alpha1
kind: Subscription
metadata:
  name: pubsub
spec:
  topic: checkout
  routes: 
    default: /orders
  pubsubname: order-pub-sub
  metadata:
    queueType: quorum

Time-to-live

You can set a time-to-live (TTL) value at either the message or component level. Set default component-level TTL using the component spec ttlInSeconds field in your component.

Note

If you set both component-level and message-level TTL, the default component-level TTL is ignored in favor of the message-level TTL.

Related links

• Basic schema for a Dapr component in the Related links section
• Read this guide for instructions on configuring pub/sub components
• Pub/Sub building block