Service invocation API reference

Detailed documentation on the service invocation API

Dapr provides users with the ability to call other applications that are using Dapr with a unique named identifier (appId), or HTTP endpoints that are not using Dapr. This allows applications to interact with one another via named identifiers and puts the burden of service discovery on the Dapr runtime.

Invoke a method on a remote Dapr app

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

HTTP Request

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

Invoke a method on a non-Dapr endpoint

This endpoint lets you invoke a method on a non-Dapr endpoint using an HTTPEndpoint resource name, or a Fully Qualified Domain Name (FQDN) URL.

HTTP Request

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

PATCH/POST/GET/PUT/DELETE http://localhost:<daprPort>/v1.0/invoke/<FQDN URL>/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
XXX Upstream status returned
400 Method name not given
403 Invocation forbidden by access control
500 Request failed

URL Parameters

Parameter Description
daprPort the Dapr port
appID the App ID associated with the remote app
HTTPEndpoint name the HTTPEndpoint resource associated with the external endpoint
FQDN URL Fully Qualified Domain Name URL to invoke on the external endpoint
method-name the name of the method or url to invoke on the remote app

Note, all URL parameters are case-sensitive.

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 or non-Dapr endpoint, Dapr sends the request, along with the headers and body, on the <method-name> endpoint.

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

Cross namespace invocation

On hosting platforms that support namespaces, Dapr app IDs conform to a valid FQDN format that includes the target namespace. For example, the following string contains the app ID (myApp) in addition to the namespace the app runs in (production).

myApp.production

Namespace supported platforms

  • Kubernetes

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 response body.

In case when your service listens on a more nested path (e.g. /api/v1/add), Dapr implements a full reverse proxy so you can append all the necessary path fragments to your request URL like this:

http://localhost:3500/v1.0/invoke/mathService/method/api/v1/add

In case you are invoking mathService on a different namespace, you can use the following URL:

http://localhost:3500/v1.0/invoke/mathService.testing/method/api/v1/add

In this URL, testing is the namespace that mathService is running in.

Non-Dapr Endpoint Example

If the mathService service was a non-Dapr application, then it could be invoked using service invocation via an HTTPEndpoint, as well as a Fully Qualified Domain Name (FQDN) URL.

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

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

Next Steps


Last modified July 19, 2024: Fixed typo in links (#4267) (32fce1d)