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Opinionated, caching, retrying fetch client

Package Exports

  • make-fetch-happen
  • make-fetch-happen/cache

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (make-fetch-happen) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

make-fetch-happen npm version license Travis AppVeyor Coverage Status

make-fetch-happen is a Node.js library that implements the fetch API, including cache support, request pooling, proxies, retries, and more!

Install

$ npm install --save make-fetch-happen

Table of Contents

Example

const fetch = require('make-fetch-happen')

fetch('https://registry.npmjs.org/make-fetch-happen', {
  cacheManager: './my-cache' // cache will be written here
}).then(res => res.json()).then(body => {
  console.log(`got ${body.name} from web`)
  return fetch('https://registry.npmjs.org/make-fetch-happen', {
    cacheManager: './my-cache',
    cache: 'no-cache' // forces a conditional request
  })
}).then(res => {
  console.log(res.status) // 304! cache validated!
  return res.json().then(body => {
    console.log(`got ${body.name} from cache`)
  })
})

Features

  • Follows fetch spec, using node-fetch under the hood.
  • Request pooling out of the box
  • Quite fast, really
  • Automatic HTTP-semantics-aware request retries
  • Proxy support (http, https, socks, socks4, socks5, pac)
  • Built-in request caching following full HTTP caching rules (Cache-Control, ETag, 304s, cache fallback on error, etc).
  • Customize cache storage with any Cache API-compliant Cache instance. Cache to Redis!
  • Node.js Stream support
  • Transparent gzip and deflate support
  • Subresource Integrity support
  • Literally punches nazis
  • (PENDING) Range request caching and resuming

Contributing

The make-fetch-happen team enthusiastically welcomes contributions and project participation! There's a bunch of things you can do if you want to contribute! The Contributor Guide has all the information you need for everything from reporting bugs to contributing entire new features. Please don't hesitate to jump in if you'd like to, or even ask us questions if something isn't clear.

All participants and maintainers in this project are expected to follow Code of Conduct, and just generally be excellent to each other.

Please refer to the Changelog for project history details, too.

Happy hacking!

API

> fetch(uriOrRequest, [opts]) -> Promise<Response>

This function implements most of the fetch API: given a uri string or a Request instance, it will fire off an http request and return a Promise containing the relevant response.

If opts is provided, the node-fetch-specific options will be passed to that library. There are also additional options specific to make-fetch-happen that add various features, such as HTTP caching, integrity verification, proxy support, and more.

Example
fetch('https://google.com').then(res => res.buffer())

> fetch.defaults([defaultUrl], [defaultOpts])

Returns a new fetch function that will call make-fetch-happen using defaultUrl and defaultOpts as default values to any calls.

A defaulted fetch will also have a .defaults() method, so they can be chained.

Example
const fetch = require('make-fetch-happen').defaults({
  cacheManager: './my-local-cache'
})

fetch('https://registry.npmjs.org/make-fetch-happen') // will always use the cache

> node-fetch options

The following options for node-fetch are used as-is:

  • method
  • body
  • redirect
  • follow
  • timeout
  • compress
  • size

These other options are modified or augmented by make-fetch-happen:

  • headers - Default User-Agent set to make-fetch happen. Connection is set to keep-alive or close automatically depending on opts.agent.
  • agent
    • If agent is null, an http or https Agent will be automatically used. By default, these will be http.globalAgent and https.globalAgent.
    • If opts.proxy is provided and opts.agent is null, the agent will be set to a proxy-agent instance.
    • If opts.agent is false or an object is provided, it will be used as the request-pooling agent for this request.

For more details, see the documentation for node-fetch itself.

> make-fetch-happen options

make-fetch-happen augments the node-fetch API with additional features available through extra options. The following extra options are available:

> opts.cacheManager

Either a String or a Cache. If the former, it will be assumed to be a Path to be used as the cache root for cacache.

If an object is provided, it will be assumed to be a compliant Cache instance. Only Cache.match(), Cache.put(), and Cache.delete() are required. Options objects will not be passed in to match() or delete().

By implementing this API, you can customize the storage backend for make-fetch-happen itself -- for example, you could implement a cache that uses redis for caching, or simply keeps everything in memory. Most of the caching logic exists entirely on the make-fetch-happen side, so the only thing you need to worry about is reading, writing, and deleting, as well as making sure fetch.Response objects are what gets returned.

You can refer to cache.js in the make-fetch-happen source code for a reference implementation.

The default cache manager also adds the following headers to cached responses:

  • X-Local-Cache: Path to the cache the content was found in
  • X-Local-Cache-Key: Unique cache entry key for this response
  • X-Local-Cache-Hash: Specific integrity hash for the cached entry
  • X-Local-Cache-Time: UTCString of the cache insertion time for the entry

Using cacache, a call like this may be used to manually fetch the cached entry:

const h = response.headers
cacache.get(h.get('x-local-cache'), h.get('x-local-cache-key'))

// grab content only, directly:
cacache.get.byDigest(h.get('x-local-cache'), h.get('x-local-cache-hash'))
Example
fetch('https://registry.npmjs.org/make-fetch-happen', {
  cacheManager: './my-local-cache'
}) // -> 200-level response will be written to disk

fetch('https://npm.im/cacache', {
  cacheManager: new MyCustomRedisCache(process.env.PORT)
}) // -> 200-level response will be written to redis

A possible (minimal) implementation for MyCustomRedisCache:

const bluebird = require('bluebird')
const redis = require("redis")
bluebird.promisifyAll(redis.RedisClient.prototype)
class MyCustomRedisCache {
  constructor (opts) {
    this.redis = redis.createClient(opts)
  }
  match (req) {
    return this.redis.getAsync(req.url).then(res => {
      if (res) {
        const parsed = JSON.parse(res)
        return new fetch.Response(parsed.body, {
          url: req.url,
          headers: parsed.headers,
          status: 200
        })
      }
    })
  }
  put (req, res) {
    return res.buffer().then(body => {
      return this.redis.setAsync(req.url, JSON.stringify({
        body: body,
        headers: res.headers.raw()
      }))
    }).then(() => {
      // return the response itself
      return res
    })
  }
  'delete' (req) {
    return this.redis.unlinkAsync(req.url)
  }
}

> opts.cache

This option follows the standard fetch API cache option. This option will do nothing if opts.cacheManager is null. The following values are accepted (as strings):

  • default - Fetch will inspect the HTTP cache on the way to the network. If there is a fresh response it will be used. If there is a stale response a conditional request will be created, and a normal request otherwise. It then updates the HTTP cache with the response.
  • no-store - Fetch behaves as if there is no HTTP cache at all.
  • reload - Fetch behaves as if there is no HTTP cache on the way to the network. Ergo, it creates a normal request and updates the HTTP cache with the response.
  • no-cache - Fetch creates a conditional request if there is a response in the HTTP cache and a normal request otherwise. It then updates the HTTP cache with the response.
  • force-cache - Fetch uses any response in the HTTP cache matching the request, not paying attention to staleness. If there was no response, it creates a normal request and updates the HTTP cache with the response.
  • only-if-cached - Fetch uses any response in the HTTP cache matching the request, not paying attention to staleness. If there was no response, it returns a network error. (Can only be used when request’s mode is "same-origin". Any cached redirects will be followed assuming request’s redirect mode is "follow" and the redirects do not violate request’s mode.)

(Note: option descriptions are taken from https://fetch.spec.whatwg.org/#http-network-or-cache-fetch)

Example
// Will error with ENOTCACHED if we haven't already cached this url
fetch('https://registry.npmjs.org/make-fetch-happen', {
  cacheManager: './my-cache',
  cache: 'only-if-cached'
})

// Will refresh any local content and cache the new response
fetch('https://registry.npmjs.org/make-fetch-happen', {
  cacheManager: './my-cache',
  cache: 'reload'
})

// Will use any local data, even if stale. Otherwise, will hit network.
fetch('https://registry.npmjs.org/make-fetch-happen', {
  cacheManager: './my-cache',
  cache: 'force-cache'
})

> opts.proxy

A string URI or an object with options to be passed directly to proxy-agent. Options available may vary depending on the proxy type. Refer the proxy-agent's documentation for more details.

Example
fetch('https://registry.npmjs.org/make-fetch-happen', {
  proxy: 'https://corporate.yourcompany.proxy:4445'
})

fetch('https://registry.npmjs.org/make-fetch-happen', {
  proxy: {
    protocol: 'https:',
    hostname: 'corporate.yourcompany.proxy',
    port: 4445,
    ca: process.env.CERTIFICATE_AUTHORITY
  }
})

> opts.retry

An object that can be used to tune request retry settings. Requests are retried if they result in a 500-level http status, or if the request fails entirely with an error. make-fetch-happen will never retry POST requests - it will only retry idempotent requests (GET, HEAD, PUT, DELETE, PATCH, etc), and those only if opts.body is NOT a stream.

If opts.retry is false, requests will never be retried.

The following retry options are available:

  • retries
  • factor
  • minTimeout
  • maxTimeout
  • randomize

For details on what each of these do, refer to the retry documentation.

Example
fetch('https://flaky.site.com', {
  retry: {
    retries: 10,
    randomize: true
  }
})

fetch('http://reliable.site.com', {
  retry: false
})

> opts.integrity

Matches the response body against the given Subresource Integrity metadata. If verification fails, the request will fail with an EINTEGRITY error.

integrity may either be a string or an ssri Integrity-like.

Example
fetch('https://registry.npmjs.org/make-fetch-happen/-/make-fetch-happen-1.0.0.tgz', {
  integrity: 'sha1-o47j7zAYnedYFn1dF/fR9OV3z8Q='
}) // -> ok

fetch('https://malicious-registry.org/make-fetch-happen/-/make-fetch-happen-1.0.0.tgz'. {
  integrity: 'sha1-o47j7zAYnedYFn1dF/fR9OV3z8Q='
}) // Error: EINTEGRITY

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