RocketMQ

Component format

To setup RocketMQ pubsub, create a component of type pubsub.rocketmq. See this guide on how to create and apply a pubsub configuration.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: rocketmq-pubsub
spec:
  type: pubsub.rocketmq
  version: v1
  metadata:
    - name: instanceName
      value: dapr-rocketmq-test
    - name: consumerGroup
      value: dapr-rocketmq-test-g-c
    - name: producerGroup 
      value: dapr-rocketmq-test-g-p
    - name: nameSpace
      value: dapr-test
    - name: nameServer
      value: "127.0.0.1:9876,127.0.0.2:9876"
    - name: retries
      value: 3
    - name: consumerModel
      value: "clustering"
    - name: consumeOrderly
      value: false

Spec metadata fields

For backwards-compatibility reasons, the following values in the metadata are supported, although their use is discouraged.

Setup RocketMQ

See https://rocketmq.apache.org/docs/quick-start/ to setup a local RocketMQ instance.

Per-call metadata fields

Partition Key

When invoking the RocketMQ pub/sub, it’s possible to provide an optional partition key by using the metadata query param in the request url.

You need to specify rocketmq-tag , "rocketmq-key" , rocketmq-shardingkey , rocketmq-queue in metadata

Example:

curl -X POST http://localhost:3500/v1.0/publish/myRocketMQ/myTopic?metadata.rocketmq-tag=?&metadata.rocketmq-key=?&metadata.rocketmq-shardingkey=key&metadata.rocketmq-queue=1 \
  -H "Content-Type: application/json" \
  -d '{
        "data": {
          "message": "Hi"
        }
      }'

QueueSelector

The RocketMQ component contains a total of five queue selectors. The RocketMQ client provides the following queue selectors:

• HashQueueSelector
• RandomQueueSelector
• RoundRobinQueueSelector
• ManualQueueSelector

To learn more about these RocketMQ client queue selectors, read the RocketMQ documentation.

The Dapr RocketMQ component implements the following queue selector:

• DaprQueueSelector

This article focuses on the design of DaprQueueSelector.

DaprQueueSelector

DaprQueueSelector integrates three queue selectors:

• HashQueueSelector
• RoundRobinQueueSelector
• ManualQueueSelector

DaprQueueSelector gets the queue id from the request parameter. You can set the queue id by running the following:

http://localhost:3500/v1.0/publish/myRocketMQ/myTopic?metadata.rocketmq-queue=1

The ManualQueueSelector is implemented using the method above.

Next, the DaprQueueSelector tries to:

• Get a ShardingKey
• Hash the ShardingKey to determine the queue id.

You can set the ShardingKey by doing the following:

http://localhost:3500/v1.0/publish/myRocketMQ/myTopic?metadata.rocketmq-shardingkey=key

If the ShardingKey does not exist, the RoundRobin algorithm is used to determine the queue id.

Related links

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