Add maxRequestsPerBatch to batchMiddleware.

Author: richardwu

src/middlewares/__tests__/batch-test.js

@@ -554,4 +554,63 @@ describe('middlewares/batch', () => {
       );
     });
   });
+
+  describe('option `maxRequestsPerBatch`', () => {
+    beforeEach(() => {
+      fetchMock.restore();
+    });
+
+    it('should split batch requests based on max requests limit', async () => {
+      // Set up mocks for single and batch requests
+      fetchMock.mock({
+        matcher: '/graphql',
+        response: {
+          status: 200,
+          body: { data: {} },
+        },
+        method: 'POST',
+      });
+
+      fetchMock.mock({
+        matcher: '/graphql/batch',
+        response: {
+          status: 200,
+          body: [{ data: {} }, { data: {} }, { data: {} }, { data: {} }, { data: {} }],
+        },
+        method: 'POST',
+      });
+
+      // Create a network layer with maxRequestsPerBatch set to 2
+      const rnl = new RelayNetworkLayer([batchMiddleware({ maxRequestsPerBatch: 2 })]);
+
+      // Create 5 mock requests
+      const req1 = mockReq(1);
+      const req2 = mockReq(2);
+      const req3 = mockReq(3);
+      const req4 = mockReq(4);
+      const req5 = mockReq(5);
+
+      // Execute all requests simultaneously
+      await Promise.all([
+        req1.execute(rnl),
+        req2.execute(rnl),
+        req3.execute(rnl),
+        req4.execute(rnl),
+        req5.execute(rnl),
+      ]);
+
+      // Check if the requests were properly split into batches
+      const batchReqs = fetchMock.calls('/graphql/batch');
+      expect(batchReqs).toHaveLength(3); // Should create 3 batches (2 + 2 + 1 requests)
+
+      // Verify the contents of the batches
+      const firstBatchBody = JSON.parse(batchReqs[0][1].body);
+      const secondBatchBody = JSON.parse(batchReqs[1][1].body);
+      const thirdBatchBody = JSON.parse(batchReqs[2][1].body);
+
+      expect(firstBatchBody).toHaveLength(2);
+      expect(secondBatchBody).toHaveLength(2);
+      expect(thirdBatchBody).toHaveLength(1);
+    });
+  });
 });

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 = {};
@@ -94,6 +96,7 @@ export default function batchMiddleware(options?: BatchMiddlewareOpts): Middlewa
       batchUrl,
       singleton,
       maxBatchSize,
+      maxRequestsPerBatch,
       fetchOpts,
     });
   };
@@ -111,6 +114,14 @@ 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);
   }