Mongodb stream gets paused after 1 document and never unpaused, causes timeout using nodejs

Working with Data Node.js Frameworks
,
1

Hello.

I encounter the issue that sometimes (not always) mongodb stream gets paused after 1 document being processed.

Node.js 22.13.1
Node.js mongodb package 4.17.2

I do the following:

 db.collection('my-collection')
    .find({
      date: {
        $gte: start,
        $lte: end
      }
    })
    .stream({
      transform: transformDecorator()
    })
    .on('pause', () => {
      req.timeoutDebug.streamPausedAt = new Date();
    })
    .on('resume', () => {
      req.timeoutDebug.streamResumedAt = new Date();
    })
    .pipe(res);

transformDecorator contains only syncronious code.

The code works most of the time (several times a minute), but once in 1-2 hours it gets paused and never resumed.

On stream timeout I output the timeoutDebug data:

 {
  "totalTransforms":1,
  "startedAt":"2025-02-20T15:01:59.186Z", 
  "firstTransformStartedAt":"2025-02-20T15:02:11.497Z",
  "streamResumedAt":"2025-02-20T15:02:15.134Z",
  "streamPausedAt":"2025-02-20T15:02:15.141Z"
}

So here I see that stream was paused after being resumed the last time.

I struggle to understand the source of the pause events. This is critical as it affects our production system.

Any help is appreciated.

Thank you