66 lines
4.5 KiB
HTML
66 lines
4.5 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="security" content="public" />
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<meta name="Robots" content="index,follow" />
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="topic" />
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<meta name="DC.Title" content="Overview of High Availability CGI" />
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<meta name="abstract" content="High availability CGI programs use APIs to preserve the CGI’s state between successive client requests. A High availability CGI program stores its state data on the Web server and can retrieve its state even after a failure or switchover of the HTTP Server or system." />
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<meta name="description" content="High availability CGI programs use APIs to preserve the CGI’s state between successive client requests. A High availability CGI program stores its state data on the Web server and can retrieve its state even after a failure or switchover of the HTTP Server or system." />
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<meta name="DC.Relation" scheme="URI" content="rzaieparcgi.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2002,2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2002,2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="rzag3ch4ovrvwhghavailcgi" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Overview of High Availability CGI</title>
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</head>
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<body id="rzag3ch4ovrvwhghavailcgi"><a name="rzag3ch4ovrvwhghavailcgi"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Overview of High Availability CGI</h1>
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<div><p>High availability CGI programs use APIs to preserve the CGI’s state
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between successive client requests. A High availability CGI program stores
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its state data on the Web server and can retrieve its state even after a failure
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or switchover of the HTTP Server or system.</p>
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<p>Although maintaining a CGI program’s state across multiple requests is
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a concept used by both Persistent CGI and High availability CGI programs,
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the mechanisms used by the two types of programs are significantly different
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and a High Availability CGI program should not be confused with a Persistent
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CGI program.</p>
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<p>During the configuration of a Web server, the server administrator indicates
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whether CGI programs are allowed to be cluster-enabled High Availability CGI
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programs. If the server receives a request for a CGI program that is allowed
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to be Highly Available (HA), the Web server passes to the CGI an environment
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variable that indicates the CGI may be cluster-enabled. The server also creates
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and passes a unique session handle to the CGI. The CGI program must then acknowledge
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that it is a cluster-enabled HA CGI program to the server, otherwise the server
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will regard the CGI as not being cluster-enabled.</p>
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<p>The Web server associates a HA CGI program’s state with the unique session
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handle that was passed as an environment variable to the CGI. If a request
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to run the CGI is sent to the Web server, and the requested URL includes the
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specific session handle, the Web server will be able to correctly restore
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the previous state of the CGI. For this reason it is important that the session
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handle appear in all URLs that were generated by the HA CGI program to be
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returned to the client.</p>
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<p>An HA CGI program will use two APIs to maintain its state. To store state
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information on the Web server, the CGI calls the API QzhbCgiSendState. To
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receive its previous state from the Web server, the CGI should call the API
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QzhbCgiRecvState.</p>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaieparcgi.htm" title="This topic provides information about Common Gateway Interfaces (CGI).">Common Gateway Interface</a></div>
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</div>
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</div>
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</body>
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</html>
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