react-relay-network-layer/es/middleware/batch.js

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

/* eslint-disable no-param-reassign */
import { isFunction } from '../utils';
// Max out at roughly 100kb (express-graphql imposed max)
const DEFAULT_BATCH_SIZE = 102400;
export default function batchMiddleware(options) {
  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 = {};
  return next => req => {
    // do not batch mutations unless allowMutations = true
    if (req.relayReqType === 'mutation' && !allowMutations) {
      return next(req);
    }

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

function passThroughBatch(req, next, opts) {
  const {
    singleton
  } = opts; // req.body as FormData can not be batched!

  if (global.FormData && req.body instanceof FormData) {
    return next(req);
  }

  const bodyLength = req.body.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;
    const {
      requestMap
    } = singleton.batcher;
    const 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) {
  const batcher = {
    bodySize: 2,
    // account for '[]'
    requestMap: {},
    acceptRequests: true
  };
  setTimeout(() => {
    batcher.acceptRequests = false;

    try {
      sendRequests(batcher.requestMap, next, opts).then(() => finalizeUncompleted(batcher.requestMap)).catch(() => finalizeUncompleted(batcher.requestMap));
    } catch (e) {
      finalizeUncompleted(batcher.requestMap, e);
    }
  }, opts.batchTimeout);
  return batcher;
}

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

  if (ids.length === 1) {
    // SEND AS SINGLE QUERY
    const request = requestMap[ids[0]];
    return next(request.req).then(res => {
      request.completeOk(res);
      request.duplicates.forEach(r => r.completeOk(res));
    });
  } else if (ids.length > 1) {
    // SEND AS BATCHED QUERY
    // $FlowFixMe
    const url = isFunction(opts.batchUrl) ? opts.batchUrl(requestMap) : opts.batchUrl;
    const req = {
      url,
      relayReqId: `BATCH_QUERY:${ids.join(':')}`,
      relayReqMap: requestMap,
      relayReqType: 'batch-query',
      method: 'POST',
      headers: {
        Accept: '*/*',
        'Content-Type': 'application/json'
      },
      body: `[${ids.map(id => requestMap[id].req.body).join(',')}]`
    };
    return next(req).then(batchResponse => {
      const payload = batchResponse ? batchResponse.payload : null;

      if (!Array.isArray(payload)) {
        throw new Error('Wrong response from server');
      }

      const responseHasIds = payload.every(response => response.id);

      if (!responseHasIds && ids.length !== payload.length) {
        throw new Error(`Server returned a different number of responses than requested.
            It's not possible to correlate requests and responses`);
      }

      payload.forEach((res, i) => {
        if (!res) return;
        const request = responseHasIds ? requestMap[res.id] : requestMap[ids[i]];

        if (request) {
          const responsePayload = copyBatchResponse(batchResponse, res);
          request.completeOk(responsePayload);
        }
      });
    }).catch(e => {
      ids.forEach(id => {
        requestMap[id].completeErr(e);
      });
    });
  }

  return Promise.resolve();
} // check that server returns responses for all requests


function finalizeUncompleted(requestMap, e) {
  Object.keys(requestMap).forEach(id => {
    const request = requestMap[id];

    if (!request.done) {
      request.completeErr(e || new Error(`Server does not return response for request with id ${id} \n` + `Response should have following shape { "id": "${id}", "data": {} }`));
    }
  });
}

function copyBatchResponse(batchResponse, res) {
  // Fallback for graphql-graphene and apollo-server batch responses
  const payload = res.payload || res;
  return {
    ok: batchResponse.ok,
    status: batchResponse.status,
    statusText: batchResponse.statusText,
    url: batchResponse.url,
    headers: batchResponse.headers,
    payload
  };
}