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---
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type: docs
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title: "How to: Use the gRPC interface in your Dapr application"
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linkTitle: "gRPC interface"
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weight: 6000
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description: "Use the Dapr gRPC API in your application"
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---
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Dapr implements both an HTTP and a gRPC API for local calls. [gRPC](https://grpc.io/) is useful for low-latency, high performance scenarios and has language integration using the proto clients.
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[Find a list of auto-generated clients in the Dapr SDK documentation]({{< ref sdks >}}).
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The Dapr runtime implements a [proto service](https://github.com/dapr/dapr/blob/master/dapr/proto/runtime/v1/dapr.proto) that apps can communicate with via gRPC.
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In addition to calling Dapr via gRPC, Dapr supports service-to-service calls with gRPC by acting as a proxy. [Learn more in the gRPC service invocation how-to guide]({{< ref howto-invoke-services-grpc.md >}}).
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This guide demonstrates configuring and invoking Dapr with gRPC using a Go SDK application.
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## Configure Dapr to communicate with an app via gRPC
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{{< tabs "Self-hosted" "Kubernetes">}}
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<!--selfhosted-->
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{{% codetab %}}
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When running in self-hosted mode, use the `--app-protocol` flag to tell Dapr to use gRPC to talk to the app.
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```bash
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dapr run --app-protocol grpc --app-port 5005 node app.js
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```
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This tells Dapr to communicate with your app via gRPC over port `5005`.
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{{% /codetab %}}
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<!--k8s-->
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{{% codetab %}}
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On Kubernetes, set the following annotations in your deployment YAML:
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```yaml
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: myapp
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namespace: default
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labels:
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app: myapp
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spec:
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replicas: 1
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selector:
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matchLabels:
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app: myapp
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template:
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metadata:
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labels:
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app: myapp
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annotations:
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dapr.io/enabled: "true"
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dapr.io/app-id: "myapp"
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dapr.io/app-protocol: "grpc"
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dapr.io/app-port: "5005"
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...
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```
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{{% /codetab %}}
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{{< /tabs >}}
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## Invoke Dapr with gRPC
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The following steps show how to create a Dapr client and call the `SaveStateData` operation on it.
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1. Import the package:
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```go
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package main
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import (
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"context"
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"log"
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"os"
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dapr "github.com/dapr/go-sdk/client"
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)
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```
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1. Create the client:
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```go
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// just for this demo
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ctx := context.Background()
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data := []byte("ping")
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// create the client
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client, err := dapr.NewClient()
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if err != nil {
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log.Panic(err)
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}
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defer client.Close()
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```
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3. Invoke the `SaveState` method:
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```go
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// save state with the key key1
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err = client.SaveState(ctx, "statestore", "key1", data)
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if err != nil {
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log.Panic(err)
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}
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log.Println("data saved")
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```
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Now you can explore all the different methods on the Dapr client.
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## Create a gRPC app with Dapr
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The following steps will show how to create an app that exposes a server for with which Dapr can communicate.
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1. Import the package:
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```go
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package main
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import (
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"context"
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"fmt"
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"log"
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"net"
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"github.com/golang/protobuf/ptypes/any"
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"github.com/golang/protobuf/ptypes/empty"
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commonv1pb "github.com/dapr/dapr/pkg/proto/common/v1"
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pb "github.com/dapr/dapr/pkg/proto/runtime/v1"
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"google.golang.org/grpc"
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)
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```
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1. Implement the interface:
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```go
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// server is our user app
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type server struct {
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pb.UnimplementedAppCallbackServer
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}
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// EchoMethod is a simple demo method to invoke
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func (s *server) EchoMethod() string {
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return "pong"
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}
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// This method gets invoked when a remote service has called the app through Dapr
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// The payload carries a Method to identify the method, a set of metadata properties and an optional payload
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func (s *server) OnInvoke(ctx context.Context, in *commonv1pb.InvokeRequest) (*commonv1pb.InvokeResponse, error) {
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var response string
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switch in.Method {
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case "EchoMethod":
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response = s.EchoMethod()
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}
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return &commonv1pb.InvokeResponse{
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ContentType: "text/plain; charset=UTF-8",
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Data: &any.Any{Value: []byte(response)},
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}, nil
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}
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// Dapr will call this method to get the list of topics the app wants to subscribe to. In this example, we are telling Dapr
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// To subscribe to a topic named TopicA
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func (s *server) ListTopicSubscriptions(ctx context.Context, in *empty.Empty) (*pb.ListTopicSubscriptionsResponse, error) {
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return &pb.ListTopicSubscriptionsResponse{
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Subscriptions: []*pb.TopicSubscription{
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{Topic: "TopicA"},
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},
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}, nil
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}
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// Dapr will call this method to get the list of bindings the app will get invoked by. In this example, we are telling Dapr
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// To invoke our app with a binding named storage
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func (s *server) ListInputBindings(ctx context.Context, in *empty.Empty) (*pb.ListInputBindingsResponse, error) {
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return &pb.ListInputBindingsResponse{
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Bindings: []string{"storage"},
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}, nil
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}
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// This method gets invoked every time a new event is fired from a registered binding. The message carries the binding name, a payload and optional metadata
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func (s *server) OnBindingEvent(ctx context.Context, in *pb.BindingEventRequest) (*pb.BindingEventResponse, error) {
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fmt.Println("Invoked from binding")
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return &pb.BindingEventResponse{}, nil
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}
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// This method is fired whenever a message has been published to a topic that has been subscribed. Dapr sends published messages in a CloudEvents 0.3 envelope.
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func (s *server) OnTopicEvent(ctx context.Context, in *pb.TopicEventRequest) (*pb.TopicEventResponse, error) {
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fmt.Println("Topic message arrived")
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return &pb.TopicEventResponse{}, nil
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}
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```
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1. Create the server:
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```go
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func main() {
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// create listener
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lis, err := net.Listen("tcp", ":50001")
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if err != nil {
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log.Fatalf("failed to listen: %v", err)
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}
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// create grpc server
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s := grpc.NewServer()
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pb.RegisterAppCallbackServer(s, &server{})
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fmt.Println("Client starting...")
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// and start...
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if err := s.Serve(lis); err != nil {
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log.Fatalf("failed to serve: %v", err)
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}
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}
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```
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This creates a gRPC server for your app on port 50001.
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## Run the application
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{{< tabs "Self-hosted" "Kubernetes">}}
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<!--selfhosted-->
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{{% codetab %}}
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To run locally, use the Dapr CLI:
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```bash
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dapr run --app-id goapp --app-port 50001 --app-protocol grpc go run main.go
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```
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{{% /codetab %}}
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<!--k8s-->
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{{% codetab %}}
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On Kubernetes, set the required `dapr.io/app-protocol: "grpc"` and `dapr.io/app-port: "50001` annotations in your pod spec template, as mentioned above.
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{{% /codetab %}}
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{{< /tabs >}}
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## Other languages
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You can use Dapr with any language supported by Protobuf, and not just with the currently available generated SDKs.
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Using the [protoc](https://developers.google.com/protocol-buffers/docs/downloads) tool, you can generate the Dapr clients for other languages like Ruby, C++, Rust, and others.
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## Related Topics
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- [Service invocation building block]({{< ref service-invocation >}})
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- [Service invocation API specification]({{< ref service_invocation_api.md >}})
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Hannah Hunter