Lock

ap

Install

npm install -save @leverege/lock

const Lock = require( '@leverege/lock' );

Usage

In general, use the lockConfig to drive the type of shared lock. This allows the type to be driven by the environment variables setup by the deployment mechanism.

const lockConfig = process.env.LOCK_CONFIG || 
  { type : 'redis', 
    connection : {
      host : '127.0.0.1',
      port : 6379
    },
    lockOptions : { ... }
  };
const lock = Lock.create( { lockConfig, namespace : 'myApp'} )

You can destroy the Lock resources by calling:

lock.destroy()

Locking

...
const l = await lock.lock( 'myKey', 1000 )  // This will lock globally on myKey
// do work
await l.unlock()

l = await lock.lockNs( 'myKey', myValue ) // This will lock using namespaced myKey (myApp:myKey)
// do work
await l.unlock()

Extending a lock

To extend a lock, call extend( timeMs ) and use the returned lock

let l = await lock.lock( 'myKey', { ttl : 1000 } ) 
// do work
l = await l.extend( 1000 )
// do more work
l.unlock()

InMemoryLock

The InMemoryLock will lock on the instance of the lock, and will work only within the process itself.

const lock = Lock.create({ 
  type : 'inMemory',
  namespace : 'myApp', 
  retry : 0,    // the number of attempts to make before failing. Negative numbers means infinite
  delay : 100,  // time in milliseconds between lock attempts
})

// or, using lockConfig
constlock = Lock.create({ 
  namespace : 'test', 
  lockConfig : { 
    type : 'inMemory', 
    retry : 0,    // the number of attempts to make before failing. Negative numbers means infinite
    delay : 100,  // time in milliseconds between lock attempts
  } })

Redis

The Redis lock can be used to lock between processes.


const lock = Lock.create( { 
    type : 'redis',
    namespace : 'myApp', 
    connection : {
      host : '127.0.0.1',
      port : 6379
    },
    // From RedLock
    lockOptions : { 
      // the expected clock drift; for more details
      // see http://redis.io/topics/distlock
      driftFactor: 0.01, // time in ms

      // the max number of times Redlock will attempt
      // to lock a resource before erroring
      retryCount:  0,

      // the time in ms between attempts
      retryDelay:  200, // time in ms

      // the max time in ms randomly added to retries
      // to improve performance under high contention
      // see https://www.awsarchitectureblog.com/2015/03/backoff.html
      retryJitter:  100 // time in ms
    }
  } )


// Or using lockConfig

const lock = Lock.create( { 
  namespace : 'myApp', 
  lockConfig : {
    type : 'redis',
    connection : {
      host : '127.0.0.1',
      port : 6379
    },
    // From RedLock
    lockOptions : { 
      // the expected clock drift; for more details
      // see http://redis.io/topics/distlock
      driftFactor: 0.01, // time in ms

      // the max number of times Redlock will attempt
      // to lock a resource before erroring
      retryCount:  0,

      // the time in ms between attempts
      retryDelay:  200, // time in ms

      // the max time in ms randomly added to retries
      // to improve performance under high contention
      // see https://www.awsarchitectureblog.com/2015/03/backoff.html
      retryJitter:  100 // time in ms
    }
  }
} )
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