Add maxRequestsPerBatch to batchMiddleware.

Author: richardwu

src/middlewares/batch.js

@@ -20,6 +20,7 @@ export type BatchMiddlewareOpts = {|
     | ((requestList: RequestWrapper[]) => string | Promise<string>),
   batchTimeout?: number,
   maxBatchSize?: number,
+  maxRequestsPerBatch?: number,
   allowMutations?: boolean,
   method?: 'POST' | 'GET',
   headers?: Headers | Promise<Headers> | ((req: RelayRequestBatch) => Headers | Promise<Headers>),
@@ -57,6 +58,7 @@ export default function batchMiddleware(options?: BatchMiddlewareOpts): Middlewa
   const allowMutations = opts.allowMutations || false;
   const batchUrl = opts.batchUrl || '/graphql/batch';
   const maxBatchSize = opts.maxBatchSize || DEFAULT_BATCH_SIZE;
+  const maxRequestsPerBatch = opts.maxRequestsPerBatch || 0; // 0 is the same as no limit
   const singleton = {};
 
   const fetchOpts = {};
@@ -111,6 +113,10 @@ function passThroughBatch(req: RelayRequest, next, opts) {
     singleton.batcher = prepareNewBatcher(next, opts);
   }
 
+  if(singleton.batcher && opts.maxRequestsPerBatch && singleton.batcher.requestList.length + 1 > opts.maxRequestsPerBatch) {
+    singleton.batcher = prepareNewBatcher(next, opts);
+  }
+
   if (singleton.batcher.bodySize + bodyLength + 1 > opts.maxBatchSize) {
     singleton.batcher = prepareNewBatcher(next, opts);
   }