Timeout impact on Eventloop lag

[gchicoye]

Hey,

I've got an app which basically

• receives a request through Express.js
• send around 10 requests to partners through Node-Fetch
• Once all received, we analyse the responses and send back the best one

Although on normal time, the application is pretty stable, when network quality decreases and we get higher level of timeouts, the event loop lag strongly increases...

The request code looks as follows

const controller = new AbortController();
  const now = Date.now();
  const timeoutController = setTimeout(() => {
    controller.abort();
    // eslint-disable-next-line no-console
    timeoutLagHistogram.observe({ ssp }, Date.now() - now - SSP_REQUEST_TIMEOUT);
  }, SSP_REQUEST_TIMEOUT);
  const agent = (parsedUrl.protocol === 'http:') ? httpAgent : httpsAgent;

  // We add correct headers

  try {
    const config = {
      highWaterMark: 1024 * 1024,
      method,
      body: JSON.stringify(payload),
      headers: finalHeaders,
      agent,
      signal: controller.signal,
    };
    const response:Response = await fetch(endpoint, config);
    let body:string = await response.text();
    try {
      body = JSON.parse(body);
    } catch (e) { /* */ }

    const { status } = response;

    return {
      ssp,
      uri: endpoint,
      requestbody: payload,
      requestheaders: finalHeaders,
      responsebody: body,
      status,
    };
  } catch (error) {
    if (error instanceof AbortError) {
      return {
        ssp,
        uri: endpoint,
        requestbody: payload,
        requestheaders: finalHeaders,
        responsebody: '',
        status: 'TIMEOUT',
      };
    }
    if (error instanceof FetchError) {
      return {
        ssp,
        uri: endpoint,
        requestbody: payload,
        requestheaders: finalHeaders,
        responsebody: '',
        status: (error).code || 'FETCHERROR',
      };
    }

    return {
      ssp,
      uri: endpoint,
      requestbody: payload,
      requestheaders: finalHeaders,
      responsebody: '',
      status: 'OTHERERROR',
    };
  } finally {
    clearTimeout(timeoutController);
  }

Here is the current status (which I'm not happy with...)

Any idea?

Thanks!