Data-point-service NPM

DataPoint Factory

Creates a DataPoint instance with redis support

Requirements

Node 6 LTS (or higher)
Redis (Optional for development)

Install

$ npm install data-point-cache

`factory.create`

Create a new DataPoint Service Object

factory.create(options):Promise<Service>

Properties of the options argument:

option	type	description
cache	`Object`	cache specific settings
cache.isRequired	`Boolean`	false by default, if true it will throw an error
cache.redis	`Object`	redis settings passed to the ioredis constructor. For key prefixing, set keyPrefix through `cache.redis.keyPrefix`; if the value is not provided then os.hostname() will be used.

This method returns a Promise that resolves to a Service Object.

The Service Object holds a reference to a dataPoint instance.

const options = {
  entities: {
    'transform:foo': (input, acc) => 'bar'
  }
}
factory.create(options)
  .then((service) => {
    return service.dataPoint.transform('transform:foo')
  })
  .then((output) => {
    console.log(output)
    // bar
  })

Express example

const express = require('express')
const DataPoint = require('data-point')
const DataPointService = require('data-point-service')

function server (dataPoint) {
  const app = express()

  app.get('/api/hello-world', (req, res) => {
    dataPoint.resolve(`entry:HelloWorld`, req.query)
      .then((output) => {
        res.send(output)
      })
  })

  app.listen(3000, function () {
    console.log('listening on port 3000!')
  })
}

function createService () {
  return DataPointService.create({
    DataPoint,
    entities: {
      'reducer:HelloWorld': (input, acc) => 'Hello World!!'
    }
  }).then((service) => {
    return service.dataPoint
  })
}

createService()
  .then(server)

Configure entity's cache settings

To configure an entity's cache settings you must set cache configuration through the params object.

'<type>:<entity-name>': {
  params: {
    cache: {
      ttl: String|Number,
      staleWhileRevalidate: String|Number
    }
  }
}

cache.ttl

ttl: String|Number

Use cache.ttl to set an entity's cache entry Time To Live value. This value is expected to be written as a string following the format supported by ms.

Example:

Creates a request entity that when called will append an entry to redis with a TTL of 20 minutes. When the entry expires, the next request that comes through will have to re-fetch again to respond, upon success a new cache entry with same TTL will be created.

DataPointService.create({
  DataPoint,
  entities: {
    'request:getPlanets': {
      url: 'https://swapi.co/api/planets/'
      params: {
        cache: {
          ttl: '20m', // 20 minutes
        }
      }
    }
  }
})

cache.staleWhileRevalidate

staleWhileRevalidate = delta-seconds

staleWhileRevalidate value is expected to be written as a string following the format supported by ms. Alternately it may also be set to true, which tells the entity to use double the time of the value of its ttl.

Use cache.staleWhileRevalidate in conjunction with a valid cache.ttl to use the Stale While Revalidate cache pattern. When present, caches MAY serve the response in which it appears after it becomes stale, up to the indicated ttl. The cache SHOULD attempt to revalidate it asynchronously while still serving stale responses. If delta-seconds passes without the cached entity being revalidated, it SHOULD NOT continue to be served stale.

Example:

Creates a request entity that when called will append an entry to redis with no expiration (stale), at the same time it will create a controller cache entry that has the ttl value. On every request to this entity the stale value will be returned, when the control entry expires, the stale value will continue to be returned and a background process will be triggered to execute the entity and update the stale entry.

DataPointService.create({
  DataPoint,
  entities: {
    'request:getPlanets': {
      url: 'https://swapi.co/api/planets/'
      params: {
        cache: {
          ttl: '20m', // 20 minutes
          staleWhileRevalidate: true
        }
      }
    }
  }
})