HP WebQoS Peak is a software plug-in (module), which runs
inside an HTTP server. The HTTP servers currently supported are
Netscape Enterprise, Zeus, and Apache. HP WebQoS can be configured
to make certain decisions based on changing system conditions. For
example, it can admit, reject, or defer new sessions based on system
load, or to end active sessions based on the interval between requests
and/or the length of a session. In addition, HP WebQoS maintains
several operation and performance statistics which can be viewed
in a Web client window.
Viewing the Server Statistics |
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The HP WebQoS maintains a series of statistics, which can
be inspected on-line by pointing your web client (browser) to the
following URL: /hpac/about.hpac (or just /hpac/). From the about.hpac page
you can access either the Statistics table,
or the Isolate table, by selecting the appropriate
link. You can also view an explanation of what each statistic means,
by selecting the field name.
What is a Session? |
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A session is an HTTP request or sequence of HTTP requests
made to a web server by a single user. A simple session might consist
of a request for a server's home page. If that page contains
images, the session would also consist of requests for each image.
A more complicated and longer session might consist of a request
for a server's home page, following a link to a catalog,
browsing the catalog and adding items to a shopping cart, and finally
supplying payment information to complete a purchase.
When Does a Web Server Become Overloaded? |
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A web server becomes overloaded when there are too many requests
for the server to fulfill; the server runs out of resources. Requests
may be delayed or dropped. For example, a user involved in a long
session may experience poor performance or may have to reload a
page more than once for it to display.
How Does HP WebQoS Work? |
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HP WebQoS monitors the resources and the number of arriving
sessions on the web server. Based on available resources and how
HP WebQoS is configured, it will accept, defer, reject or redirect
a session. HP WebQoS makes sure the web server does not become overloaded
by deferring, rejecting or redirecting any new sessions for which
it does not have resources. It also allows an admitted session to
be completed.
When the web server's resources are available, HP
WebQoS allows the session to begin and will fulfill all requests
made during this session. HP WebQoS monitors the time between requests
as well as the length of the session. If one of these variables
exceeds the thresholds configured in HP WebQoS, the session is terminated.
Otherwise, all requests are fulfilled until the session is completed.
When the web server's resources are not available,
HP WebQoS will defer, reject or redirect the session. The web administrator
can choose to redirect the request to another URL, or serve a page
with an error message or some helpful information.
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