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spring-cloud-stream-dapr

README.md

spring-cloud-stream-dapr

Spring Cloud Stream establishes a connection between the application and the middleware, separates the logic of sending and receiving messages with specific middleware from the application, and is finally provided by Binder. Binder shields the details of the underlying MQ message middleware and decouples our application from the specific message middleware.

In addition, Spring Cloud Stream abstracts the MQ in the Spring Cloud system and provides a unified API for sending and receiving messages, in order to simplify the development of messages in Spring Cloud applications.

Combining Spring Cloud Stream and Dapr, on the one hand Dapr can make up the dependent on a specific middleware library for Spring Cloud Stream, on the other hand, Spring Cloud Stream can help application and Dapr client decoupling.

How it works

In this project, Spring Cloud Stream Dapr Binder (Dapr Binder) was implemented to strip non-business logic parts from the application, so that developers can pay more attention to the development of business logic. The entire Dapr Sidecar was regarded as an MQ. When sending messages a Grpc’s Client is activated. And when receiving messages, a Grpc’s Server is responsible for monitor Dapr’s calls. Two interfaces are opened, one is to tell Dapr which topics have I subscribed to, and the other is to receive messages from the subscribed topics.

Usage

Step 1: Pre-requisites

Before running this demo, please ensure that you have the following software installed:

Step 2: Add dependency

To use Dapr Binder, you need to add spring-cloud-stream-binder-dapr as a dependency to your Spring Cloud Stream application, as shown in the following example for Maven:

<dependency>
   <groupId>io.dapr.spring</groupId>
   <artifactId>spring-cloud-stream-binder-dapr</artifactId>
   <version>0.0.1-SNAPSHOT</version>
</dependency>

Alternatively, you can use the spring-cloud-starter-stream-dapr, as follows:

<dependency>
   <groupId>io.dapr.spring</groupId>
   <artifactId>spring-cloud-starter-stream-dapr</artifactId>
   <version>0.0.1-SNAPSHOT</version>
</dependency>

Step 3: Start dapr sidecar

The dapr run command looks for the default components directory which for Linux/MacOS is $HOME/.dapr/components and for Windows is %USERPROFILE%\.dapr\components which holds yaml definition files for components Dapr will be using at runtime. For specific purposes, you can customize your own yaml file. The following is an example yaml file for implementing kafka pubsub.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: kafka-pubsub
spec:
  type: pubsub.kafka
  initTimeout: 1m
  version: v1
  metadata:
  # Kafka broker connection setting
  - name: brokers
    value: localhost:9092
  # consumer configuration: consumer group
  - name: consumerGroup
    value: group1
  - name: authType # Required.
    value: "none"

Then use dapr run to start sidecar and your application.

dapr run --app-port 8080 --app-id test --components-path {PATH_OF_COMPONENTS_FOLDER} -- java -jar {JAR_PACKAGE_PATH_OF_YOUR_APPLICATION}

For more guidance, please refer to sample kafka.