lockclient

DynamoDB Lock Client - Golang

A golang 1.x implementation of awslabs/dynamodb-lock-client.

The Amazon DynamoDB Lock Client is a general purpose distributed locking library built for DynamoDB. The DynamoDB Lock Client supports both fine-grained and coarse-grained locking as the lock keys can be any arbitrary string, up to a certain length.^[1]

Table of Contents

• Usage
• Documentation
  • lockclient.DynamoDBLockClient
  • GetLock()
  • StopHeartbeat()
  • RemoveLock()
  • HasLock()
  • SetLevel()
• Contributing

Usage

To pull dependencies:

go get github.com/samstradling/dynamodb-lock-client-golang

For a full example see examples/basic-case/main.go.

// Setup AWS region, and, for local development only, the endpoint
config := &aws.Config{
        Region:   aws.String("eu-west-1"),
        Endpoint: aws.String("http://localhost:8000"),
    }
sess := session.Must(session.NewSession(config))
// Setup the lock client config
lockClient := &lockclient.DynamoDBLockClient{
    LockName:        "my-unique-lock-name",
    LeaseDuration:   5000 * time.Millisecond,
    HeartbeatPeriod: 1000 * time.Millisecond,
    TableName:       "LockTable",
    Client:          dynamodb.New(sess),
}

for true {
    err := lockClient.GetLock() // Try to get the lock
    if err != nil {
        break
    }
    // Keep trying every second
    time.Sleep(1 * time.Second)
}
defer lockClient.RemoveLock() // remove the lock once done

for i := 0; i < 10; i++ {
    _, err := lockClient.HasLock() // check if lock is still valid
    if err != nil {
        logrus.Debug(err)
    }
    time.Sleep(1000 * time.Millisecond) // super important action that requires a global lock
}

Documentation

import "github.com/samstradling/dynamodb-lock-client-golang"

To use, create a dynamo table with a hash key named key.

lockclient.DynamoDBLockClient

DynamoDBLockClient creates a new lock client.

lockClient := &lockclient.DynamoDBLockClient{}

DynamoDBLockClient fields:

GetLock()

Request a new lock, returns true on success.

func (d *DynamoDBLockClient) GetLock() (bool, error)

StopHeartbeat()

Stop sending lock heartbeats, any existing locks will not be removed until they expire.

func (d *DynamoDBLockClient) StopHeartbeat()

RemoveLock()

Request the removal of any existing locks.

func (d *DynamoDBLockClient) RemoveLock() error

HasLock()

Returns true if the existing lock is valid.

func (d *DynamoDBLockClient) HasLock() (bool, error)

SetLevel()

This library uses github.com/sirupsen/logrus. To set the log level use:

logrus.SetLevel(logrus.DebugLevel)
logrus.SetLevel(logrus.InfoLevel)
logrus.SetLevel(logrus.ErrorLevel)

Contributing

To develop locally you'll probably want to run a local version of dynamodb. This can be done with the following docker command:

docker run -p 8000:8000 -d amazon/dynamodb-local

The examples directory contains a script to create a local dynamodb table:

go run examples/create-local-table/main.go

Contibutions welcomed.