Overload symptoms

The symptoms of an overloaded Web server are:

* requests are served with (possibly long) delays (from 1 second to a few hundred seconds);
* 500, 502, 503, 504 HTTP errors are returned to clients (sometimes also unrelated 404 error or even 408 error may be returned);
* TCP connections are refused or reset (interrupted) before any content is sent to clients;
* in very rare cases, only partial contents are sent (but this behavior may well be considered a bug, even if it usually depends on unavailable system resources).

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