apollo-proxy-cache

Using an external graphql server on your server side rendered node application can slow down the initial render time.

This library provides an apollo-link and express (proxy) middleware setup to support a local @cache directive for queries. It comes with a default in-memory cache implementation (using Map). You can provide your own (e.g. redis etc.) by just implementing a simple interface.

Install

yarn add apollo-proxy-cache 

or 

npm install apollo-proxy-cache

Example Query

query someQuery($arg1: String!) @cache(id: "cache-key", timeout: 3600, modifier: ["arg1"])  {
    field(arg: $arg1) {
        property
    }
}

Options

| name | description | type | required | | |----------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------|----------|---| | id | static cache key | string | true | | | timeout | when the cache should be invalidated (in seconds), if unset or 0 it will be cached indefinitely. | number | false | | | modifier | path's inside any query argument that should be appended to the cache key. lodash is used for property access, so you can use . and [] delimiters (e.g. some.path[0].in.array). A resulting cache could look like $id.$firstPathsValue.$secondPathsValue etc. | Array<String> | false | |

Setup

The library requires to have body-parser (see https://www.npmjs.com/package/body-parser or similar) in the middleware chain. Please add accordingly to the setup example.

Available Caching Backends

• InMemoryCache, will store all data inside a Map
• RedisCache, will store data inside redis (requires a redis client instance).

Express

The Express middleware will either redirect the request to your graphql server or serve the request locally (depending on the @cache settings for the query). It will additionally remove the @cache directive and forward only the pure query to your server. There are no changes on your implementation required.

import { createProxyCacheMiddleware, InMemoryCache } from 'apollo-proxy-cache'
import express from 'express'
const queryCache = new InMemoryCache()
import bodyParser from 'body-parser'

const proxyMiddlewareFactory = proxyCacheMiddleware(queryCache)

const app = express()
app.use(bodyParser.json()) // setup body-parser before (or anything else that populates request.body).
const { directiveMiddleware, proxyMiddleware } = proxyMiddlewareFactory(
    { target: "http://graphql-server.com", changeOrigin: true } /* configuration object for http-proxy-middleware */
    )
// directive middleware to remove directives and handle caching
app.use( '/graphql', directiveMiddleware)

// the proxy itself
app.use( '/graphql', proxyMiddleware)

Apollo-Link Setup (on node side)

To speed up the initial rendering you can also setup the proxyCacheLink. This will skip any http request and serve directly from your cache implementation.

import { createHttpLink } from 'apollo-link-http'
import { InMemoryCache as ApolloInMemoryCache } from 'apollo-cache-inmemory'
import { from } from 'apollo-link'
import { ApolloClient } from 'apollo-client'
import { proxyCacheLink, InMemoryCache } from 'apollo-proxy-cache'

 const queryCache = new InMemoryCache() /* Make sure you use the same instance that you use in the middleware setup.*/

  const proxyCache = proxyCacheLink(queryCache)
  const cache = new ApolloInMemoryCache()

  const httpLink = createHttpLink({ uri: 'http://graphql-server.com' })

  return new ApolloClient({
    ssrMode: true,
    link: from([
      proxyCache,
      httpLink
    ]),
    cache
  })

Cache implementation's

Your cache implementation needs to implement the following interface (here in flow):

interface Cache<K, V> {
  delete(key: K): Promise<boolean>;
  get(key: K): Promise<?V>;
  set(key: K, value: V, timeout: number): Promise<Cache<K, V>>;
}

Customize the cache key

You can pass a function as second argument (type CacheKeyModifier = (?string, ?Object) => ?string) on proxyCacheLink and proxyCacheMiddleware that allows you to modify the key before saving. This is useful if your queries depend on a global context. e.g. a http header that modifies the result independend of the query parameters (e.g. Accept-Language)