react-relay-network-modern-haruska

ReactRelayNetworkModern (for Relay Modern)
==========================================
!FlowType compatible

The ReactRelayNetworkModern is a Network Layer for Relay Modern
with various middlewares which can manipulate requests/responses on the fly (change auth headers, request url or perform some fallback if request fails), batch several relay request by timeout into one http request, cache queries.

Network Layer for Relay Classic can be found here.

Migration guide from v1 to v2 can be found here.

ReactRelayNetworkModern can be used in browser, react-native or node server for rendering. Under the hood this module uses global fetch method. So if your client is too old, please import explicitly proper polyfill to your code (eg. whatwg-fetch, node-fetch or fetch-everywhere).

Install
=======

``
yarn add react-relay-network-modern
OR
npm install react-relay-network-modern --save
`

#### What if regeneratorRuntime is not defined?


I don't want to bundle regenerator-runtime with the library - it's a largish dependency and there's a good chance that the user is already including code which depends on it (eg. via babel-polyfill). If we bundle it they'll get a duplicate copy and that's bad.

So if you got regeneratorRuntime is not defined you should do the following:
`js
import 'regenerator-runtime/runtime';
import { RelayNetworkLayer } from 'react-relay-network-modern';
`

#### Different builds
This library contains different builds for any purposes:
`js
// Default import for using in any browser
// last 5 versions, ie 9, defaults
import { RelayNetworkLayer } from 'react-relay-network-modern';

// For SSR on node 8 and above (native async/await)
import { RelayNetworkLayer } from 'react-relay-network-modern/node8';

// Source code without Flowtype declarations
import { RelayNetworkLayer } from 'react-relay-network-modern/es';
`


Middlewares
===========

$3


- your custom inline middleware - see example below where added credentials and headers to the fetch method.
- next => req => { / your modification of 'req' object / return next(req); }
- urlMiddleware - for manipulating fetch url on fly via thunk.
- url - string for single request. Can be Promise or function(req). (default: /graphql).
- method - string, for request method type (default: POST)
- headers - Object with headers for fetch. Can be Promise or function(req).
- credentials - string, setting for fetch method, eg. 'same-origin' (default: empty).
- also you may provide mode, cache, redirect options for fetch method, for details see fetch spec.
- cacheMiddleware - for caching same queries you may use this middleware. It will skip (do not cache) mutations and FormData requests.
- size - max number of request in cache, least-recently updated entries purged first (default: 100).
- ttl - number in milliseconds, how long records stay valid in cache (default: 900000, 15 minutes).
- onInit - function(cache) which will be called once when cache is created. As first argument you receive QueryResponseCache instance from relay-runtime.
- allowMutations - allow to cache Mutation requests (default: false)
- allowFormData - allow to cache FormData requests (default: false)
- authMiddleware - for adding auth token, and refreshing it if gets 401 response from server.
- token - string which returns token. Can be function(req) or Promise. If function is provided, then it will be called for every request (so you may change tokens on fly).
- tokenRefreshPromise: - function(req, res) which must return promise or regular value with a new token. This function is called when server returns 401 status code. After receiving a new token, middleware re-run query to the server seamlessly for Relay.
- allowEmptyToken - allow made a request without Authorization header if token is empty (default: false).
- prefix - prefix before token (default: 'Bearer ').
- header - name of the HTTP header to pass the token in (default: 'Authorization').
- If you use auth middleware with retry, retry must be used before auth. Eg. if token expired when retries apply, then retry can call auth middleware again.
- retryMiddleware - for request retry if the initial request fails.
- fetchTimeout - number in milliseconds that defines in how much time will request timeout after it has been sent to the server again (default: 15000).
- retryDelays - array of millisecond that defines the values on which retries are based on (default: [1000, 3000]). Or it may be a function (attempt: number) => number | false which returns a timeout in milliseconds for retry or false for disabling retry.
- statusCodes - array of response status codes which will fire up retryMiddleware. Or it may be a function (statusCode: number, req, res) => boolean which makes retry if returned true. (default: status < 200 or status > 300).
- forceRetry - function(cb, delay), when request is delayed for next retry, middleware will call this function and pass to it a callback and delay time. When you call this callback cb, middleware will proceed request immediately (default: false).
- allowMutations - by default retries disabled for mutations, you may allow process retries for them passing true. (default: false)
- allowFormData - by default retries disabled for file Uploads, you may enable it passing true (default: false)
- batchMiddleware - gather some period of time relay-requests and sends it as one http-request. You server must support batch request, how to setup your server
- batchUrl - string. Url of the server endpoint for batch request execution. Can be function(requestMap) or Promise. (default: /graphql/batch)
- batchTimeout - integer in milliseconds, period of time for gathering multiple requests before sending them to the server. Will delay sending of the requests on specified in this option period of time, so be careful and keep this value small. (default: 0)
- maxBatchSize - integer representing maximum size of request to be sent in a single batch. Once a request hits the provided size in length a new batch request is ran. Actual for hardcoded limit in 100kb per request in express-graphql module. (default: 102400 characters, roughly 100kb for 1-byte characters or 200kb for 2-byte characters)
- allowMutations - by default batching disabled for mutations, you may enable it passing true (default: false)
- method - string, for request method type (default: POST)
- headers - Object with headers for fetch. Can be Promise or function(req).
- credentials - string, setting for fetch method, eg. 'same-origin' (default: empty).
- also you may provide mode, cache, redirect options for fetch method, for details see fetch spec.
- loggerMiddleware - for logging requests and responses.
- logger - log function (default: console.log.bind(console, '[RELAY-NETWORK]'))
- An example of req/res output in console:
- perfMiddleware - simple time measure for network request.
- logger - log function (default: console.log.bind(console, '[RELAY-NETWORK]'))
- errorMiddleware - display errors data to console from graphql response. If you want see stackTrace for errors, you should provide formatError to express-graphql (see example below where graphqlServer accept formatError function).
- logger - log function (default: console.error.bind(console))
- prefix - prefix message (default: [RELAY-NETWORK] GRAPHQL SERVER ERROR:)

$3

`js
import { Environment, RecordSource, Store } from 'relay-runtime';
import {
RelayNetworkLayer,
urlMiddleware,
batchMiddleware,
loggerMiddleware,
errorMiddleware,
perfMiddleware,
retryMiddleware,
authMiddleware,
cacheMiddleware,
} from 'react-relay-network-modern';

const network = new RelayNetworkLayer([
cacheMiddleware({
size: 100, // max 100 requests
ttl: 900000, // 15 minutes
}),
urlMiddleware({
url: (req) => Promise.resolve('/graphql'),
}),
batchMiddleware({
batchUrl: (requestMap) => Promise.resolve('/graphql/batch'),
batchTimeout: 10,
}),
__DEV__ ? loggerMiddleware() : null,
__DEV__ ? errorMiddleware() : null,
__DEV__ ? perfMiddleware() : null,
retryMiddleware({
fetchTimeout: 15000,
retryDelays: (attempt) => Math.pow(2, attempt + 4) * 100, // or simple array [3200, 6400, 12800, 25600, 51200, 102400, 204800, 409600],
forceRetry: (cb, delay) => { window.forceRelayRetry = cb; console.log('call forceRelayRetry() for immediately retry! Or wait ' + delay + ' ms.'); },
statusCodes: [500, 503, 504]
}),
authMiddleware({
token: () => store.get('jwt'),
tokenRefreshPromise: (req) => {
console.log('[client.js] resolve token refresh', req);
return fetch('/jwt/refresh')
.then(res => res.json())
.then(json => {
const token = json.token;
store.set('jwt', token);
return token;
})
.catch(err => console.log('[client.js] ERROR can not refresh token', err));
},
}),

// example of the custom inline middleware
next => async req => {
req.fetchOpts.method = 'GET'; // change default POST request method to GET
req.fetchOpts.headers['X-Request-ID'] = uuid.v4(); // add X-Request-ID to request headers
req.fetchOpts.credentials = 'same-origin'; // allow to send cookies (sending credentials to same domains)
// req.fetchOpts.credentials = 'include'; // allow to send cookies for CORS (sending credentials to other domains)

console.log('RelayRequest', req);

const res = await next(req);
console.log('RelayResponse', res);

return res;
}
], opts); // as second arg you may pass advanced options for RRNL

const source = new RecordSource();
const store = new Store(source);
const environment = new Environment({ network, store });
`

$3


RelayNetworkLayer may accept additional options:
`js
const middlewares = []; // array of middlewares
const options = {}; // optional advanced options
const network = new RelayNetworkLayer(middlewares, options);
`
Available options:
- subscribeFn - if you use subscriptions in your app, you may provide this function which will be passed to RelayNetwork.
- beforeFetch - if you need synchronously render app on the client side from already generated payload by server (SSR) this options is for you. Some details can be found here.

$3

For performant server-side rendering with node 8 and above recommended to use special build of this network layer. Also you may execute graphql directly without http-request if you write custom middleware. All this recommendations present in following example:

`js
const RRNL = require('react-relay-network-modern/node8');
const graphql = require('graphql').graphql;
const schema = require('schema').default;
return new RRNL.RelayNetworkLayer([
() => async req => {
const res = await graphql({
schema,
source: req.getQueryString(),
variableValues: req.getVariables(),
contextValue: {},
});
// console.dir(res, { colors: true, depth: 5 });
return RRNL.RelayNetworkLayerResponse.createFromGraphQL(res);
},
]);
`

$3

Middlewares on bottom layer use fetch method. So req is compliant with a fetch() options. And res can be obtained via resPromise.then(res => ...), which returned by fetch().

Middlewares have 3 phases:
- setup phase, which runs only once, when middleware added to the NetworkLayer
- capturing phase, when you may change request object, and pass it down via next(req)
- bubbling phase, when you may change response promise, made re-request or pass it up unchanged

Basic skeleton of middleware:
`js
export default function skeletonMiddleware(opts = {}) {
// [SETUP PHASE]: here you can process opts, when you create Middleware

return next => async req => {
// [CAPTURING PHASE]: here you can change req object, before it will pass to following middlewares.
// ...some code which modify req

const res = await next(req); // pass request to following middleware and get response promise from it

// [BUBBLING PHASE]: here you may change response of underlying middlewares, via promise syntax
// ...some code, which process req

return res; // return response to upper middleware
};
}
`

Middlewares use LIFO (last in, first out) stack. Or simply put - use compose function. So if you pass such middlewares [M1(opts), M2(opts)] to NetworkLayer it will be work such way:
- call setup phase of M1 with its opts
- call setup phase of M2 with its opts
- for each request
- call capture phase of M1
- call capture phase of M2
- call fetch method
- call bubbling phase of M2
- call bubbling phase of M1
- chain to resPromise.then(res => res.json()) and pass this promise for resolving/rejecting Relay requests.


Batching several requests into one
==================================

Joseph Savona wrote: For legacy reasons, Relay splits "plural" root queries into individual queries. In general we want to diff each root value separately, since different fields may be missing for different root values.

Also if you use react-relay-router and have multiple root queries in one route pass, you may notice that default network layer will produce several http requests.

So for avoiding multiple http-requests, the ReactRelayNetworkModern is the right way to combine it in single http-request.

$3

#### ...on server
Firstly, you should prepare server to proceed the batch request:

`js
import express from 'express';
import graphqlHTTP from 'express-graphql';
import { graphqlBatchHTTPWrapper } from 'react-relay-network-modern';
import bodyParser from 'body-parser';
import myGraphqlSchema from './graphqlSchema';

const port = 3000;
const server = express();

// setup standart graphqlHTTP express-middleware
const graphqlServer = graphqlHTTP({
schema: myGraphqlSchema,
formatError: (error) => ({ // better errors for development. stack used in gqErrors middleware
message: error.message,
stack: process.env.NODE_ENV === 'development' ? error.stack.split('\n') : null,
}),
});

// declare route for batch query
server.use('/graphql/batch',
bodyParser.json(),
graphqlBatchHTTPWrapper(graphqlServer)
);

// declare standard graphql route
server.use('/graphql',
graphqlServer
);

server.listen(port, () => {
console.log(The server is running at http://localhost:${port}/);
});
`
More complex example of how you can use a single DataLoader for all (batched) queries within a one HTTP-request.

If you are on Koa@2, koa-graphql-batch provides the same functionality as graphqlBatchHTTPWrapper (see its docs for usage example).

#### ...on client
And right after server side ready to accept batch queries, you may enable batching on the client:

`js
const network = new RelayNetworkLayer([
batchMiddleware({
batchUrl: '/graphql/batch', // <--- route for batch queries
}),
]);
`

$3


Internally batching in NetworkLayer prepare list of queries [ {id, query, variables}, ...] sends it to server. And server returns list of responces [ {id, payload}, ...], (where id is the same value as client requested for identifying which data goes with which query, and payload is standard response of GraphQL server: { data, error }`).

Contribute
==========
I actively welcome pull requests with code and doc fixes.
Also if you made great middleware and want share it within this module, please feel free to open PR.

CHANGELOG

License
=======
MIT