li1234yun / go-sdk

Dapr SDK for go

Dapr SDK for Go

Client library to accelerate Dapr application development in go. This client supports all public Dapr API and focuses on developer productivity.

Usage

Assuming you already have installed go

Dapr go client includes two packages: client (for invoking public Dapr API) and service (to create services in go that can be invoked by Dapr, this is sometimes refereed to as "callback").

Client

Import Dapr go client package:

import "github.com/dapr/go-sdk/client"

Quick start

package main

import (
    dapr "github.com/dapr/go-sdk/client"
)

func main() {
    client, err := dapr.NewClient()
    if err != nil {
        panic(err)
    }
    defer client.Close()
    //TODO: use the client here, see below for examples 
}

Assuming you have Dapr CLI installed locally, you can then launch your app locally like this:

dapr run --app-id example-service \
         --app-protocol grpc \
         --app-port 50001 \
         go run main.go

Check the example folder for working Dapr go client examples.

Usage

The Dapr go client supports following functionality:

State

For simple use-cases, Dapr client provides easy to use methods for Save, Get, and Delete:

ctx := context.Background()
data := []byte("hello")
store := "my-store" // defined in the component YAML 

// save state with the key key1
if err := client.SaveState(ctx, store, "key1", data); err != nil {
    panic(err)
}

// get state for key key1
item, err := client.GetState(ctx, store, "key1")
if err != nil {
    panic(err)
}
fmt.Printf("data [key:%s etag:%s]: %s", item.Key, item.Etag, string(item.Value))

// delete state for key key1
if err := client.DeleteState(ctx, store, "key1"); err != nil {
    panic(err)
}

For more granular control, the Dapr go client exposed SetStateItem type which can be use to gain more control over the state operations and allow for multiple items to be saved at once:

item1 := &dapr.SetStateItem{
    Key:  "key1",
    Etag: "2",
    Metadata: map[string]string{
        "created-on": time.Now().UTC().String(),
    },
    Value: []byte("hello"),
    Options: &dapr.StateOptions{
        Concurrency: dapr.StateConcurrencyLastWrite,
        Consistency: dapr.StateConsistencyStrong,
    },
}

item2 := &dapr.SetStateItem{
    Key:  "key2",
    Metadata: map[string]string{
        "created-on": time.Now().UTC().String(),
    },
    Value: []byte("hello again"),
}

item3 := &dapr.SetStateItem{
    Key:  "key3",
    Etag: "1",
    Value: []byte("hello again"),
}

if err := client.SaveStateItems(ctx, store, item1, item2, item3); err != nil {
    panic(err)
}

Similarly, GetBulkItems method provides a way to retrieve multiple state items in a single operation:

keys := []string{"key1", "key2", "key3"}
items, err := client.GetBulkItems(ctx, store, keys, 100)

And the ExecuteStateTransaction method to transactionally execute multiple upsert or delete operations.

ops := make([]*dapr.StateOperation, 0)

op1 := &dapr.StateOperation{
    Type: dapr.StateOperationTypeUpsert,
    Item: &dapr.SetStateItem{
        Key:   "key1",
        Value: []byte(data),
    },
}
op2 := &dapr.StateOperation{
    Type: dapr.StateOperationTypeDelete,
    Item: &dapr.SetStateItem{
        Key:   "key2",
    },
}
ops = append(ops, op1, op2)
meta := map[string]string{}
err := testClient.ExecuteStateTransaction(ctx, store, meta, ops)

PubSub

To publish data onto a topic the Dapr client provides a simple method:

data := []byte(`{ "id": "a123", "value": "abcdefg", "valid": true }`)
if err := client.PublishEvent(ctx, "component-name", "topic-name", data); err != nil {
    panic(err)
}

Service Invocation

To invoke a specific method on another service running with Dapr sidecar, the Dapr client provides two options. To invoke a service without any data:

resp, err = client.InvokeService(ctx, "service-name", "method-name") 

And to invoke a service with data:

content := &dapr.DataContent{
    ContentType: "application/json",
    Data:        []byte(`{ "id": "a123", "value": "demo", "valid": true }`),
}

resp, err := client.InvokeServiceWithContent(ctx, "service-name", "method-name", content)

Bindings

Similarly to Service, Dapr client provides two methods to invoke an operation on a Dapr-defined binding. Dapr supports input, output, and bidirectional bindings.

For simple, output only biding:

in := &dapr.BindingInvocation{ Name: "binding-name", Operation: "operation-name" }
err = client.InvokeOutputBinding(ctx, in)

To invoke method with content and metadata:

in := &dapr.BindingInvocation{
    Name:      "binding-name",
    Operation: "operation-name",
    Data: []byte("hello"),
    Metadata: map[string]string{"k1": "v1", "k2": "v2"},
}

out, err := client.InvokeBinding(ctx, in)

Secrets

The Dapr client also provides access to the runtime secrets that can be backed by any number of secrete stores (e.g. Kubernetes Secrets, Hashicorp Vault, or Azure KeyVault):

opt := map[string]string{
    "version": "2",
}

secret, err := client.GetSecret(ctx, "store-name", "secret-name", opt)

Service (callback)

In addition to this Dapr API client, Dapr go SDK also provides service package to bootstrap your Dapr callback services in either gRPC or HTTP. Instructions on how to use it are located here

Contributing to Dapr go client

See the Contribution Guide to get started with building and developing.