Coyote Point Systems Equalizer GX Series Administration Manual Download

Page: 435 / 866

Using Active Content Verification (ACV)

Active Content Verification (ACV) is a mechanism for checking the validity of a server. When you
enable ACV for a server pool, Equalizer requests data from each server instance in the server pool
and verifies that the returned data contains a character string that indicates that the data is valid.
You can use ACV with most network services that support a text-based request/response protocol,
such as HTTP. Note, however, that you cannot use ACV with Layer 4 UDP clusters.

ACV checking is performed as part of the high-level TCP probes that Equalizer sends to every
server by default. To enable ACV, you specify an

ACV response

string for a server pool. Equalizer

which will then search for the

ACV response

string in the first 1024 characters of the server’s

response to the high-level TCP probes. If the ACV response string is not found, the server is
marked down. An ACV probe can be specified if the service running on the server’s

probe port

requires input in order to respond.

How ACV works is best explained using a simple example. The HTTP protocol enables you to
establish a connection to a server, request a file, and read the result.

> telnet www.myserver.com 80 >>>>

User requests connection to server.

Connected to www.myserver.com >>>>

Telnet indicates connection is established.

> GET /index.html >>>>

User sends request for HTML page.

Server responds with requested page.

<TITLE>Welcome to our Home Page </TITLE>

</HTML>

Connection closed by foreign host >>>>

Telnet indicates server connection closed.

Equalizer can perform the same exchange automatically and verify the server’s response by
checking the returned data against an expected result.

Specifying an

ACV probe string

and an

ACV response string

basically automates the above exchange

Equalizer uses the probe string to request data from each server. To verify the server’s content,
Equalizer searches the returned data for the response string. For example, you can use “

GET

/index.html

” as the

ACV probe string

and you can set the response string to some text, such as

“

Welcome

” appears on the home page.

Similarly, if you have a Web server with a PHP application that accesses a database, you can use
ACV to ensure that all the components of the application are working. You could set up a PHP page
called

test.php

that accesses the database and returns a page containing “ALL OK” if there are no

problems.

Then you would enter and ACV Query and an ACV Response String using either the CLI or GUI. :

If the page that is returned contains the correct response string in the first 1000 characters,
including headers) the server is marked “up”; if “ALL OK” were not present, the server is marked
down.

Coyote Point Systems Equalizer GX Series, Administration Manual

Search results

Summary of Contents for Equalizer GX Series

Reviews:

Related manuals for Equalizer GX Series

Brands by name

Popular brands