How to limit the number of concurrent requests in web api?

Question

How to limit by code the number of concurrent requests to web application, say to 3 requests ? Am I suppose to put each servlet class into a thread and create a global counter (by creating new class)?

Answer 1

How to limit by code the number of concurrent requests to web application, say to 3 requests ? Am I suppose to put each servlet class into a thread and create a global counter (by creating new class)?

You typically rely in the web container to limit the number of concurrent requests; eg by setting limit on the number of worker threads or connections ... in the web container configurations.

Apparently, if a Tomcat server gets more requests than it can handle, it will send generic 503 responses. For more information:

• https://tomcat.apache.org/tomcat-8.5-doc/config/http.html - explains where / how the configs can be set
• Tomcat responding HTTP 503 - gives an example of what would happen ...

But how can i display to the users that the wed reached its limit (like 3 requests)?

If you want to limit specific request types and display specific responses to the user, then you probably will need to implement this within each servlet, using a counter, etcetera.

But the problem with trying to do "nice" things when the server is overloaded is that doing the nice things tends to increase the load. This is particularly important:

• when your server is grossly inadequate for the actual load from (real) users, or
• when someone is DoS'ing you, either accidentally or deliberately.