How-To: Use a lock

Learn how to use distributed locks to provide exclusive access to a resource

Now that you’ve learned what the Dapr distributed lock API building block provides, learn how it can work in your service. In this guide, an example application acquires a lock using the Redis lock component to demonstrate how to lock resources. For a list of supported lock stores, see this reference page.

In the diagram below, two instances of the same application acquire a lock, where one instance is successful and the other is denied.

The diagram below shows two instances of the same application acquiring a lock, where one instance is successful and the other is denied

The diagram below shows two instances of the same application, where one instance releases the lock and the other instance is then able to acquire the lock.

Diagram showing releasing a lock from multiple instances of same application

The diagram below shows two instances of different applications, acquiring different locks on the same resource.

The diagram below shows two instances of different applications, acquiring different locks on the same resource

Configure a lock component

Save the following component file to the default components folder on your machine.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: lockstore
spec:
  type: lock.redis
  metadata:
  - name: redisHost
    value: localhost:6379
  - name: redisPassword
    value: <PASSWORD>

Acquire lock


curl -X POST http://localhost:3500/v1.0-alpha1/lock/lockstore
   -H 'Content-Type: application/json'
   -d '{"resourceId":"my_file_name", "lockOwner":"random_id_abc123", "expiryInSeconds": 60}'

using System;
using Dapr.Client;

namespace LockService
{
    class Program
    {
        static async Task Main(string[] args)
        {
            string DAPR_LOCK_NAME = "lockstore";
            var client = new DaprClientBuilder().Build();

            using (var fileLock = await client.Lock(DAPR_LOCK_NAME, "my_file_name", "random_id_abc123", 60))
            {
                if (fileLock.Success)
                {
                    Console.WriteLine("Success");
                }
                else
                {
                    Console.WriteLine($"Failed to lock {fileName}.");
                }
            }
        }
    }
}

package main

import (
    "fmt"

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

func main() {
    client, err := dapr.NewClient()
    if err != nil {
        panic(err)
    }
    defer client.Close()
    
    resp, err := client.TryLockAlpha1(ctx, "lockstore", &dapr.LockRequest{
			LockOwner:         "random_id_abc123",
			ResourceID:      "my_file_name",
			ExpiryInSeconds: 60,
		})

    fmt.Println(resp.Success)
}

Unlock existing lock


curl -X POST http://localhost:3500/v1.0-alpha1/unlock/lockstore
   -H 'Content-Type: application/json'
   -d '{"resourceId":"my_file_name", "lockOwner":"random_id_abc123"}'

using System;
using Dapr.Client;

namespace LockService
{
    class Program
    {
        static async Task Main(string[] args)
        {
            string DAPR_LOCK_NAME = "lockstore";
            var client = new DaprClientBuilder().Build();

            var response = await client.Unlock(DAPR_LOCK_NAME, "my_file_name", "random_id_abc123"));
            Console.WriteLine(response.LockStatus);
        }
    }
}

package main

import (
    "fmt"

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

func main() {
    client, err := dapr.NewClient()
    if err != nil {
        panic(err)
    }
    defer client.Close()
    
    resp, err := client.UnlockAlpha1(ctx, "lockstore", &UnlockRequest{
			LockOwner:    "random_id_abc123",
			ResourceID: "my_file_name",
		})

    fmt.Println(resp.Status)
}

Next steps

Read the distributed lock API overview to learn more.


Last modified July 27, 2022: typo and quick grammar pass (#2676) (15b65c28)