Support for AbortController and signal in NodeJS

[twswilliansantos]

Hello Couchnode team!

I have an API made with nodejs and express and I'm currently using couchbase: 4.7.1.

I recently implemented a new feature in this API, which consists by applying a request abortion, using the class AbortController and signal.

The request is proper cancelled, as per requested, although, I couldn't find an option in the couchbase that allows me to send this signal and get in-flights couchbase query cancelled when the related request is aborted.

If I understand correctly, even with a request been cancelled, the in-flight query keeps running in couchbase server.

Is that possible, somehow, pass the AbortController instance to the couchbase connection or query in order to cancel in-flight queries?

In case this option is not available in couchbase nodejs library, is it possible to have this implemented?

Here's some code examples to show what I'd like to implement:

// Called at the beginning of application
app.use(
  '/',
  cors({ origin: true, credentials: true }),
  bodyParser.json({ limit: '50mb' }),

  expressMiddleware(server, {
    context: async ({ req, res }) => {
      const abortController = new AbortController();

      // Client disconnected/aborted - stop waiting on downstream work for this request.
      req.on('close', () => {
        if (!res.writableEnded) abortController.abort();
      });

      const query = 'any N1QL query here';
      const parameters = { param1: 'value1', param2: 'value2' };

      executeQuery(query, parameters, abortController.signal);
    },
  })
);

// Function that executes the query
async function executeQuery(query, parameters = {}, abortSignal) {
  if (abortSignal?.aborted) {
    const abortErr = new Error(`Query aborted before execution`);
    abortErr.name = ABORT_ERROR_NAME;
    throw abortErr;
  }

  const { cluster } = await CouchbaseConnectionManager.getConnection();

  const result = await cluster.query(query, { 
      parameters, 
      signal: abortSignal // Here I pass the abort signal so that the query execution can be cancelled
    }); 

  return result.rows;
};

[thejcfactor]

Hi @twswilliansantos -- thanks for providing some details. Definitely a reasonable request. Bu, let me provide a little background:

The current architecture of the SDK is that it sits on top of the C++ core (we use it for performant I/O with the server). As it stands, the C++ core doesn't offer HTTP streaming (at least not yet). So, the core issues the query request, buffers the entire response, and then hands it back to Node. Node's cluster.query() streaming via row events is simply replaying that already-buffered response.

Since the full response is already buffered before Node ever sees it, there isn't a meaningful point where a cancellation would interrupt anything.

I do think we're close to having HTTP streaming land in the C++ core. But, I also need to talk w/ the team to see why we currently don't have a cancellation mechanism with query.

Will hold off on this request for now, but I'll follow up with an update once I have more details. Leaving the issue open until then.