react-relay-network-modern/lib/middlewares/legacyBatch.js.flow

Network Layer for React Relay and Express (Batch Queries, AuthToken, Logging, Retry)

/* @flow */
/* eslint-disable no-param-reassign */

import { isFunction } from '../utils';
import RelayRequestBatch from '../RelayRequestBatch';
import RelayRequest from '../RelayRequest';
import type RelayResponse from '../RelayResponse';
import type { Middleware, FetchOpts } from '../definition';
import { RRNLBatchMiddlewareError } from './batch';

// Max out at roughly 100kb (express-graphql imposed max)
const DEFAULT_BATCH_SIZE = 102400;

type Headers = { [name: string]: string };

export type BatchMiddlewareOpts = {|
  batchUrl?: string | Promise<string> | ((requestMap: BatchRequestMap) => string | Promise<string>),
  batchTimeout?: number,
  maxBatchSize?: number,
  allowMutations?: boolean,
  method?: 'POST' | 'GET',
  headers?: Headers | Promise<Headers> | ((req: RelayRequestBatch) => Headers | Promise<Headers>),
  // Avaliable request modes in fetch options. For details see https://fetch.spec.whatwg.org/#requests
  credentials?: $PropertyType<FetchOpts, 'credentials'>,
  mode?: $PropertyType<FetchOpts, 'mode'>,
  cache?: $PropertyType<FetchOpts, 'cache'>,
  redirect?: $PropertyType<FetchOpts, 'redirect'>,
|};

export type BatchRequestMap = {
  [reqId: string]: RequestWrapper,
};

export type RequestWrapper = {|
  req: RelayRequest,
  completeOk: (res: Object) => void,
  completeErr: (e: Error) => void,
  done: boolean,
  duplicates: Array<RequestWrapper>,
|};

type Batcher = {
  bodySize: number,
  requestMap: BatchRequestMap,
  acceptRequests: boolean,
};

export default function legacyBatchMiddleware(options?: BatchMiddlewareOpts): Middleware {
  const opts = options || {};
  const batchTimeout = opts.batchTimeout || 0; // 0 is the same as nextTick in nodeJS
  const allowMutations = opts.allowMutations || false;
  const batchUrl = opts.batchUrl || '/graphql/batch';
  const maxBatchSize = opts.maxBatchSize || DEFAULT_BATCH_SIZE;
  const singleton = {};

  const fetchOpts = {};
  if (opts.method) fetchOpts.method = opts.method;
  if (opts.credentials) fetchOpts.credentials = opts.credentials;
  if (opts.mode) fetchOpts.mode = opts.mode;
  if (opts.cache) fetchOpts.cache = opts.cache;
  if (opts.redirect) fetchOpts.redirect = opts.redirect;
  if (opts.headers) fetchOpts.headersOrThunk = opts.headers;

  return (next) => (req) => {
    // do not batch mutations unless allowMutations = true
    if (req.isMutation() && !allowMutations) {
      return next(req);
    }

    if (!(req instanceof RelayRequest)) {
      throw new RRNLBatchMiddlewareError(
        'Relay batch middleware accepts only simple RelayRequest. Did you add batchMiddleware twice?'
      );
    }

    // req with FormData can not be batched
    if (req.isFormData()) {
      return next(req);
    }

    return passThroughBatch(req, next, {
      batchTimeout,
      batchUrl,
      singleton,
      maxBatchSize,
      fetchOpts,
    });
  };
}

function passThroughBatch(req: RelayRequest, next, opts) {
  const { singleton } = opts;

  const bodyLength = (req.fetchOpts.body: any).length;
  if (!bodyLength) {
    return next(req);
  }

  if (!singleton.batcher || !singleton.batcher.acceptRequests) {
    singleton.batcher = prepareNewBatcher(next, opts);
  }

  if (singleton.batcher.bodySize + bodyLength + 1 > opts.maxBatchSize) {
    singleton.batcher = prepareNewBatcher(next, opts);
  }

  // +1 accounts for tailing comma after joining
  singleton.batcher.bodySize += bodyLength + 1;

  // queue request
  return new Promise((resolve, reject) => {
    const relayReqId = req.getID();
    const { requestMap } = singleton.batcher;

    const requestWrapper: RequestWrapper = {
      req,
      completeOk: (res) => {
        requestWrapper.done = true;
        resolve(res);
        requestWrapper.duplicates.forEach((r) => r.completeOk(res));
      },
      completeErr: (err) => {
        requestWrapper.done = true;
        reject(err);
        requestWrapper.duplicates.forEach((r) => r.completeErr(err));
      },
      done: false,
      duplicates: [],
    };

    if (requestMap[relayReqId]) {
      /*
        I've run into a scenario with Relay Classic where if you have 2 components
        that make the exact same query, Relay will dedup the queries and reuse
        the request ids but still make 2 requests. The batch code then loses track
        of all the duplicate requests being made and never resolves or rejects
        the duplicate requests
        https://github.com/nodkz/react-relay-network-layer/pull/52
      */
      requestMap[relayReqId].duplicates.push(requestWrapper);
    } else {
      requestMap[relayReqId] = requestWrapper;
    }
  });
}

function prepareNewBatcher(next, opts): Batcher {
  const batcher: Batcher = {
    bodySize: 2, // account for '[]'
    requestMap: {},
    acceptRequests: true,
  };

  setTimeout(() => {
    batcher.acceptRequests = false;
    sendRequests(batcher.requestMap, next, opts)
      .then(() => finalizeUncompleted(batcher.requestMap))
      .catch(() => finalizeUncompleted(batcher.requestMap));
  }, opts.batchTimeout);

  return batcher;
}

async function sendRequests(requestMap: BatchRequestMap, next, opts) {
  const ids = Object.keys(requestMap);

  if (ids.length === 1) {
    // SEND AS SINGLE QUERY
    const request = requestMap[ids[0]];

    const res = await next(request.req);
    request.completeOk(res);
    request.duplicates.forEach((r) => r.completeOk(res));
    return res;
  } else if (ids.length > 1) {
    // SEND AS BATCHED QUERY

    const batchRequest = new RelayRequestBatch(ids.map((id) => requestMap[id].req));
    // $FlowFixMe
    const url = await (isFunction(opts.batchUrl) ? opts.batchUrl(requestMap) : opts.batchUrl);
    batchRequest.setFetchOption('url', url);

    const { headersOrThunk, ...fetchOpts } = opts.fetchOpts;
    batchRequest.setFetchOptions(fetchOpts);

    if (headersOrThunk) {
      const headers = await (isFunction(headersOrThunk)
        ? (headersOrThunk: any)(batchRequest)
        : headersOrThunk);
      batchRequest.setFetchOption('headers', headers);
    }

    try {
      const batchResponse = await next(batchRequest);
      if (!batchResponse || !Array.isArray(batchResponse.json)) {
        throw new RRNLBatchMiddlewareError(
          'Wrong response from server. Did your server support batch request?'
        );
      }

      batchResponse.json.forEach((payload: any) => {
        if (!payload) return;
        const request = requestMap[payload.id];
        if (request) {
          const res = createSingleResponse(batchResponse, payload);
          request.completeOk(res);
        }
      });

      return batchResponse;
    } catch (e) {
      ids.forEach((id) => {
        requestMap[id].completeErr(e);
      });
    }
  }

  return Promise.resolve();
}

// check that server returns responses for all requests
function finalizeUncompleted(requestMap: BatchRequestMap) {
  Object.keys(requestMap).forEach((id) => {
    const request = requestMap[id];
    if (!request.done) {
      request.completeErr(
        new RRNLBatchMiddlewareError(
          `Server does not return response for request with id ${id} \n` +
            `Response should have following shape { "id": "${id}", "data": {} }`
        )
      );
    }
  });
}

function createSingleResponse(batchResponse: RelayResponse, json: any): RelayResponse {
  // Fallback for graphql-graphene and apollo-server batch responses
  const data = json.payload || json;
  const res = batchResponse.clone();
  res.processJsonData(data);
  return res;
}