Description

This project explores dapr, more specifically, dapr's service invocation capability, applied to 2 microservices ran in docker containers, both written in Java:

• sender invokes service receiver's /ping method via HTTP using dapr

How to demo the PoC

• Step 1

  # stand up the docker compose stack
  $ docker compose up -d --build

• Step 2

  # check that receiving service is up and running via curl from the host
  $ curl http://localhost/ping

• Step 3

  # attach to `sender` container and run the java application in it
  $ docker compose exec sender java -jar /app/target/SenderService-1.0.jar
       

  The above command should result in { "response": "pong"} JSON object being returned from receiver/ping method

• Alternatively (Step 4)

  # run the curl command directly from within `sender` container
  $ docker compose exec sender curl http://localhost:3500/v1.0/invoke/receiver/method/ping

Explanation

• docker-compose.yml contains definitions of sender and receiver services (sender invokes receiver's 'ping' method), to enable dapr based communication between sender and receiver for each service we define service_dapr container with daprd (a.k.a. sidecar) sharing service container's network via network_mode: {namespace}:{server_name} configuration)
• Steps 3 and 4 were only possible because dapr enabled method invocation via well defined path: http://localhost:3500/v1.0/invoke/**SERVICE_NAME**/method/**API_ROUTE** where:
  • 3500 is the default dapr HTTP port
  • SERVICE_NAME - is the name of the service receiver in the network
  • API_ROUTE - is the URL of the method to inkoke relative to the service receiver
• Final detail: (actually optional) we use traefik as api proxy to give receiver's method the route /ping relative to the receiver's host, e.g. curl http://localhost/ping run from the host invokes this microservice. In other words, without traefik, we can just use curl http://localhost:8087 command for the same result

issues

• issue with unavailable docker.sock on linux

 # chown docker.sock 
 $ sudo chown $(whoami):$(whoami) /var/run/docker.sock