multi-region-limiter

Multi-region load balancing.
In this package, redis is required because redis is used to manage the region's quota limit.

Installation

npm install --save multi-region-limiter

Usage

import MultiRegionLimiter from 'multi-region-limiter';
// const MultiRegionLimiter = require('multi-region-limiter');

// MultiRegionLimiter instance.
const limiter = new MultiRegionLimiter({
    prefix: 'myapp',// Key prefix for region assignment information to be stored in Redis. Defaults to ‘myapp’.
    host: '127.0.0.1',// Redis hostname. Default is "127.0.0.1".
    port: 6379,// Redis port. Default is 6379.
});

// Register a region for load balancing
await limiter.register({region: 'us-west1', quota: 100, duration: 60});
await limiter.register({region: 'us-west2', quota: 100, duration: 60});
await limiter.register({region: 'us-west3', quota: 50, duration: 60});

// Get regions that can be allocated
const region = await limiter.consume();

API

MultiRegionLimiter class

Instance methods

• constructor()

  Parameters:

  • {string} options.prefix Key prefix for region assignment information to be stored in Redis. Defaults to ‘myapp’.
  • {string} options.host Redis hostname. Default is "127.0.0.1".
  • {number} options.port Redis port. Default is 6379.
  • {boolean} options.debug If enabled, debug logs are output. Default is disabled.

• consume()

  Get an assignable region.
  If no allocatable region is found, waits and retries until an allocatable region is freed if the maximum retry option (options.maxRetry) is enabled (greater than or equal to 1).
  If no allocatable regions are found, returns undefined.

  Parameters:

  • {number} options.maxRetry Maximum number of retries if no single assignable region is found. The default is 3. If you do not want to retry, set -1.
  • {boolean} options.disconnect When enabled, Redis is disconnected, allowing testing in scenarios where Redis is not available. Default is disabled.

  Return value:

  {Promise<string|undefined>} Assignable region name.

  Exceptions:

  • {Error} Unable to connect to Redis or unexpected errors occurred.

• register()

  Register a region.

  Parameters:

  • {string} options.region Region Name. Region name must be unique.
  • {number} options.quota Allocatable number of times per duration.
  • {number} options.duration Number of seconds before the allocated count is reset.

  Return value:

  {Promise<void>}

  Exceptions:

  • {Error} Duplicate region name. Please use a unique region name.

• getTimeUntilAllocation()

  Get milliseconds until next region assignment.

  Return value:

  {Promise<number>} Number of milliseconds that can be allocated next.

Author

Takuya Motoshima

• github/takuya-motoshima
• twitter/TakuyaMotoshima
• facebook/takuya.motoshima.7

License

MIT