Why respond time is 100 times slower than processing request on server? - google-cloud-platform

Question

I have a computer engine server in us-east1-b zone.
n1-highmem-4 (4 vCPUs, 26 GB memory) with 50 GB SSD and everything shows normal in monitoring graphs.
we are using this server as rails based RESTful API.
The problem is when we send a request to the server it takes very long time to receive the response.
Here is our server log:
as you can see it took 00:01 second to response to the request
and here is the response received by postman:
as you can see X-Runtime is 0.036319 as expected but we received the response in 50374 ms which means almost 1 min after server response!

Answer 1

I hope this answer can help people with same problem.
Passenger's highly optimized load balancer assumes that Ruby apps can handle 1 (or thread-limited amount of) concurrent connection(s). This is usually the case and results in optimal load-balancing. But endpoints that deal with SSE/Websockets can handle many more concurrent connections, so the assumption leads to degraded performance.
You can use the force max concurrent requests per process configuration option to override this. The example below shows how to set the concurrency to unlimited for /special_websocket_endpoint:
server {
listen 80;
server_name www.example.com;
root /webapps/my_app/public;
passenger_enabled on;
# Use default concurrency for the app. But for the endpoint
# /special_websocket_endpoint, force a different concurrency.
location /special_websocket_endpoint {
passenger_app_group_name foo_websocket;
passenger_force_max_concurrent_requests_per_process 0;
}
}
In Passenger 5.0.21 and below the option above was not available yet. In those versions there is a workaround for Ruby apps. Enter code below into config.ru to set the concurrency (on the entire app).