fix(message-stream): support multiple inbound message packets

If there was enough data buffered to read multiple messages, the
MessageStream would currently callback to the underlaying Writable
callback multiple times. Also fixed here is that the callback would
not be called in the event that there wasn't enough data to process
a single message

NODE-2437

Author: mbroadst

lib/cmap/message_stream.js

@@ -39,32 +39,7 @@ class MessageStream extends Duplex {
     const buffer = this[kBuffer];
     buffer.append(chunk);
 
-    while (buffer.length >= 4) {
-      const sizeOfMessage = buffer.readInt32LE(0);
-      if (sizeOfMessage < 0) {
-        callback(new MongoParseError(`Invalid message size: ${sizeOfMessage}`));
-        return;
-      }
-
-      if (sizeOfMessage > this.maxBsonMessageSize) {
-        callback(
-          new MongoParseError(
-            `Invalid message size: ${sizeOfMessage}, max allowed: ${this.maxBsonMessageSize}`
-          )
-        );
-        return;
-      }
-
-      if (sizeOfMessage > buffer.length) {
-        callback();
-        return;
-      }
-
-      const messageBuffer = buffer.slice(0, sizeOfMessage);
-      buffer.consume(sizeOfMessage);
-
-      processMessage(this, messageBuffer, callback);
-    }
+    processIncomingData(this, callback);
   }
 
   _read(/* size */) {
@@ -125,7 +100,36 @@ function canCompress(command) {
   return !uncompressibleCommands.has(commandName);
 }
 
-function processMessage(stream, message, callback) {
+function processIncomingData(stream, callback) {
+  const buffer = stream[kBuffer];
+  if (buffer.length < 4) {
+    callback();
+    return;
+  }
+
+  const sizeOfMessage = buffer.readInt32LE(0);
+  if (sizeOfMessage < 0) {
+    callback(new MongoParseError(`Invalid message size: ${sizeOfMessage}`));
+    return;
+  }
+
+  if (sizeOfMessage > stream.maxBsonMessageSize) {
+    callback(
+      new MongoParseError(
+        `Invalid message size: ${sizeOfMessage}, max allowed: ${stream.maxBsonMessageSize}`
+      )
+    );
+    return;
+  }
+
+  if (sizeOfMessage > buffer.length) {
+    callback();
+    return;
+  }
+
+  const message = buffer.slice(0, sizeOfMessage);
+  buffer.consume(sizeOfMessage);
+
   const messageHeader = {
     length: message.readInt32LE(0),
     requestId: message.readInt32LE(4),
@@ -142,7 +146,12 @@ function processMessage(stream, message, callback) {
       new ResponseType(stream.bson, message, messageHeader, messageBody, responseOptions)
     );
 
-    callback();
+    if (buffer.length >= 4) {
+      processIncomingData(stream, callback);
+    } else {
+      callback();
+    }
+
     return;
   }
 
@@ -176,7 +185,11 @@ function processMessage(stream, message, callback) {
       new ResponseType(stream.bson, message, messageHeader, messageBody, responseOptions)
     );
 
-    callback();
+    if (buffer.length >= 4) {
+      processIncomingData(stream, callback);
+    } else {
+      callback();
+    }
   });
 }
 

test/unit/cmap/message_stream.test.js

@@ -8,7 +8,12 @@ const expect = require('chai').expect;
 
 function bufferToStream(buffer) {
   const stream = new Readable();
-  stream.push(buffer);
+  if (Array.isArray(buffer)) {
+    buffer.forEach(b => stream.push(b));
+  } else {
+    stream.push(buffer);
+  }
+
   stream.push(null);
   return stream;
 }
@@ -24,6 +29,31 @@ describe('Message Stream', function() {
         ),
         documents: [{ ismaster: 1 }]
       },
+      {
+        description: 'valid multiple OP_REPLY',
+        expectedMessageCount: 4,
+        data: Buffer.from(
+          '370000000100000001000000010000000000000000000000000000000000000001000000130000001069736d6173746572000100000000' +
+            '370000000100000001000000010000000000000000000000000000000000000001000000130000001069736d6173746572000100000000' +
+            '370000000100000001000000010000000000000000000000000000000000000001000000130000001069736d6173746572000100000000' +
+            '370000000100000001000000010000000000000000000000000000000000000001000000130000001069736d6173746572000100000000',
+          'hex'
+        ),
+        documents: [{ ismaster: 1 }]
+      },
+      {
+        description: 'valid OP_REPLY (partial)',
+        data: [
+          Buffer.from('37', 'hex'),
+          Buffer.from('0000', 'hex'),
+          Buffer.from(
+            '000100000001000000010000000000000000000000000000000000000001000000130000001069736d6173746572000100000000',
+            'hex'
+          )
+        ],
+        documents: [{ ismaster: 1 }]
+      },
+
       {
         description: 'valid OP_MSG',
         data: Buffer.from(
@@ -32,6 +62,19 @@ describe('Message Stream', function() {
         ),
         documents: [{ $db: 'admin', ismaster: 1 }]
       },
+      {
+        description: 'valid multiple OP_MSG',
+        expectedMessageCount: 4,
+        data: Buffer.from(
+          '370000000100000000000000dd0700000000000000220000001069736d6173746572000100000002246462000600000061646d696e0000' +
+            '370000000100000000000000dd0700000000000000220000001069736d6173746572000100000002246462000600000061646d696e0000' +
+            '370000000100000000000000dd0700000000000000220000001069736d6173746572000100000002246462000600000061646d696e0000' +
+            '370000000100000000000000dd0700000000000000220000001069736d6173746572000100000002246462000600000061646d696e0000',
+          'hex'
+        ),
+        documents: [{ $db: 'admin', ismaster: 1 }]
+      },
+
       {
         description: 'Invalid message size (negative)',
         data: Buffer.from('ffffffff', 'hex'),
@@ -46,10 +89,13 @@ describe('Message Stream', function() {
       it(test.description, function(done) {
         const bson = new BSON();
         const error = test.error;
+        const expectedMessageCount = test.expectedMessageCount || 1;
         const inputStream = bufferToStream(test.data);
         const messageStream = new MessageStream({ bson });
 
+        let messageCount = 0;
         messageStream.on('message', msg => {
+          messageCount++;
           if (error) {
             done(new Error(`expected error: ${error}`));
             return;
@@ -63,7 +109,9 @@ describe('Message Stream', function() {
               .that.deep.equals(test.documents);
           }
 
-          done();
+          if (messageCount === expectedMessageCount) {
+            done();
+          }
         });
 
         messageStream.on('error', err => {