title: GCP internal http(s) load balancer timeout after 300s
body: <p>Recently, I've a problem with the internal http(s) load balancer on GCP, about the <strong>timeout</strong> of backend service (an instance group). After 300 seconds, the API calling to LB will be failed with 408 HTTP response.</p>
  <ul>
  <li>I have an internal HTTPS load balancer (LB) on GCP.</li>
  <li>First, I call a quick API through LB, that worked normally.</li>
  <li>Then I set timeout for backend service to 10 seconds then call the slow API (say, <strong>500</strong> seconds to complete the request). The error response happens after 10 seconds as expected.</li>
  <li>But when I set the timeout to <strong>1000</strong> seconds and call the slow API, I received the error timeout response after only exactly <strong>300</strong> seconds.</li>
  </ul>
  <p>I also increase the <em>Connection draining timeout</em> to 1000 seconds, but it still doesn't work.</p>
  <p>Is the any parameter I need to set to allow API with reply time more than 300 seconds? Thank you.</p>