service_invocation_api.md

Service Invocation API Specification

Dapr provides users with the ability to call other applications that have unique ids. This functionality allows apps to interact with one another via named identifiers and puts the burden of service discovery on the Dapr runtime.

Contents

• Invoke a Method on a Remote Dapr App

Invoke a method on a remote dapr app

This endpoint lets you invoke a method in another Dapr enabled app.

HTTP Request

POST/GET/PUT/DELETE http://localhost:<daprPort>/v1.0/invoke/<appId>/method/<method-name>

HTTP Response codes

When a service invokes another service with Dapr, the status code of the called service will be returned to the caller. If there's a network error or other transient error, Dapr will return a 500 error with the detailed error message.

In case a user invokes Dapr over HTTP to talk to a gRPC enabled service, an error from the called gRPC service will return as 500 and a successful response will return as 200OK.

Code	Description
500	Request failed

URL Parameters

Parameter	Description
daprPort	the Dapr port
appId	the App ID associated with the remote app
method-name	the name of the method or url to invoke on the remote app

Request Contents

In the request you can pass along headers:

{
  "Content-Type": "application/json"
}

Within the body of the request place the data you want to send to the service:

{
  "arg1": 10,
  "arg2": 23,
  "operator": "+"
}

Request received by invoked service

Once your service code invokes a method in another Dapr enabled app, Dapr will send the request, along with the headers and body, to the app on the <method-name> endpoint.

The Dapr app being invoked will need to be listening for and responding to requests on that endpoint.

Examples

You can invoke the add method on the mathService service by sending the following:

curl http://localhost:3500/v1.0/invoke/mathService/method/add \
  -H "Content-Type: application/json"
  -d '{ "arg1": 10, "arg2": 23}'

The mathService service will need to be listening on the /add endpoint to receive and process the request.

For a Node app this would look like:

app.post('/add', (req, res) => {
  let args = req.body;
  const [operandOne, operandTwo] = [Number(args['arg1']), Number(args['arg2'])];
  
  let result = operandOne / operandTwo;
  res.send(result.toString());
});

app.listen(port, () => console.log(`Listening on port ${port}!`));

The response from the remote endpoint will be returned in the request body.