About The Project

I made a distributed lock that can be used by other services. It solves data-setting race issues. I mostly made it as an exercise in TDD.

Built With

• Typescript
• Node
• Express
• Redis

Getting Started

yarn install

Usage

Prerequisites

• yarn
• redis

How to run

yarn start

config

Configure by creating a .env file in the root directory with the following keys:

• PORT - port on which to launch this node app. Default is 3000
• HOST - hostname. Default is localhost
• REDIS_PORT - redis port. Default is 6379
• REDIS_HOST - Redis host. Default is localhost
• DEFAULT_EXPIRY - Default expiry time. Default is 1 second.

Alternatively, command line options can be specified:

-p     --port <value>           specify launch port
-H     --host <value>           specify launch host
-P     --redis-port <value>     specify redis port
-R     --redis-host <string>    specify redis host
-N     --no-redis               use in-memory key repository instead of redis
-E     --default-expiry <ms>    set default lock duration expiry time (ms)

The no redis option uses an in-memory repository instead of redis.

Program will keep track of locked keys identified by a uid string. Other services can access its API:

Method	Path	Input	Description	Output
POST	/lock	uid: string - unique id of service making API call keys: string | string[] - keys to lock exp?: number (optional) - length of lock (ms). Equals default if not specified.	Service locks specified keys either until it is unlocked or after expiry.	response is JSON containing either: error or tokens:{   key,   version }[]
POST	/unlock	uid: string tokens: {key: string, version: number}[] - keys to lock - should use the tokens response of the lock object.	Unlock the tokens by including the tokens received when they were locked.	unlocked: string - keys that have been unlocked.
POST	/check	keys: string | string []	Checks whether all specified keys are locked	locked: boolean - true if at least 1 key is locked

License

Distributed under the GPLv3 License. See LICENSE for more information.