Re: How can I assure a high QoS in a web application ?

From:
Lew <lew@nowhere.com>
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 14 Dec 2006 19:09:13 -0500
Message-ID:
<oqGdneQ85sE3ehzYnZ2dnUVZ_vmqnZ2d@comcast.com>
Red Orchid wrote:

While (true) {
    Execute a tolerance test for concurrent requests <= 200.


The point of testing for actual performance is vital. Much of your design will
be for process, not code; you need to define protocols for measurement of
runtime performance, identification of failures in QoS, and locations of the
weak points.

Be careful what you measure. Generally it is impossible to guarantee display
time to the browser, since that depends on network factors outside the
application. One can aim for, if not assure, time from receipt of request to
dispatch of response. Likewise, one can measure the latter but likely not the
former.

Your process protocols most definitely will include logging policies.

Consider statistical guarantees over absolutes. That is, aim for "response
time t for at least x % of requests" where x < 100. (Limiting variance on
service times may be very valuable.)

These sorts of definitions tend to make the problem space more approachable
and the solution able to evolve toward the most practical results.

- Lew

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