TypeError: Cannot read properties of null (reading 'finishWrite')

[alenakhineika]

Something has changed in the latest Insiders so our MongoDB extension CI started to fail with errors (any branch but here is an example):

Cannot read properties of null (reading 'finishWrite'): TypeError: Cannot read properties of null (reading 'finishWrite')
	at JSStreamSocket.finishWrite (node:internal/js_stream_socket:211:12)
	at Immediate.<anonymous> (node:internal/js_stream_socket:196:14)
	at process.processImmediate (node:internal/timers:466:21)

Do you have any idea what might cause it so we can make changes on our side? Might it be something with your dependencies?

[deepak1556]

Runtime has no changes with insiders, this seems like a regression from the recent http proxy changes based on similar errors in upstream. Passing onto @chrmarti

From a quick look the extension relies on https://github.com/mongodb-js/compass/tree/main/packages/data-service package which makes network connection. @alenakhineika it would be great if you can reduce the test case to a minimal extension sample for us to debug this issue further. Thanks!

[alenakhineika]

Unfortunately, we haven't been able to isolate the issue for a minimal extension sample so far.

To reproduce the problem, you can follow these steps:

1. Clone the repository and install the extension.
2. Run the following commands in the terminal:

npm ci
npm run compile
npm test

When running all tests, you may observe multiple failures with the TypeError: Cannot read properties of null (reading 'finishWrite'). However, when running the failed tests separately, they randomly may or may not fail again, which makes it hard to identify the cause of the issue. It is possible that your proxy patches might be the right place to look for further investigation.

[chrmarti]

Maybe a related discussion: nodejs/node#46094

[alenakhineika]

Found it. The place in our code that fails with the latest Insiders is fetch with a biggish timeout. I created a minimal test so you can try it, but here is the code snippet for a quick look:

test('minimal test with fetch', async () => {
    const fetch = require('cross-fetch');
    let unparsedCIDRs;
    try {
      // The uncaught `TypeError: Cannot read properties of null (reading 'finishWrite')`
      // is being thrown for several fetch calls with 5000 timeout:
      // https://github.com/mongodb-js/mongodb-cloud-info/blob/main/index.js#L30
      for (let i = 0; i < 15; i++) {
        unparsedCIDRs = await fetch(CIDRS_URL, { timeout: 5000 }).then((res) =>
          res.json()
        );
      }
    } catch (error) {
      console.log(error);
    }
    assert.notStrictEqual(unparsedCIDRs, null);
});