yogesh hingmire wrote:
While planning / designing to build a web app that must scale to 2000
concurrent users, distributed across 5 Tomcat nodes in a cluster, Apache at
the front of course and the ability to serve 20 concurrent requests per
seconds during business hours, with a page response time of 5 seconds, how
would we go about the ask ? What Apache / Tomcat / System (CPU/JVM)
parameters should be considered for this design ?
I will provide the ABC, and leave the details for someone else.
You have 20 requests arriving per second, and it takes 5 seconds to process one request
and return the response.
So, over time, it will look like this
Time new requests requests in-process requests terminated
0 20 20 0
+1s 20 40 0
+2s 20 60 0
+3s 20 80 0
+4s 20 100 0
+5s 20 100 20
+6s 20 100 40
+7s 20 100 60
etc...
So, in principle, and assuming nothing else is going on, you need 100 concurrent threads
in Tomcat to process these requests.
(I would take a healthy margin of security and double that).
Whether for that you need a cluster of Tomcats is another discussion.
And how much memory you need to allocate to your Tomcat(s) JVM(s) is a function of what
your webapp needs, to process one request.
The numer of concurrent users should be relatively irrelevant, if all you mean by that is
that some of these requests come from the same user, but they are otherwise independent of
one another.
Note that I have a suspicion that what you describe as "requests" above probably only
count the requests to your webapp code, and do not count the additional requests for
stylesheets, images, etc.. which may be embedded in any page that the user's browser
eventually displays.
So unless you plan on serving those directly from the Apache httpd front-end, you should
take them into account too.
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