IBM AS/400E Chapter 4. Using Persistent CGI Programs

Chapter 4. Using Persistent CGI Programs

Overview of Persistent CGI .........81

Named Activation Groups ........81

Accept-HTSession CGI Header .......81

HTTimeoutCGIHeader.........82

Considerations for using Persistent CGI

Programs..............82

Persistent CGI Program Example ......83

Persistent CGI is an extension to the CGI interface that allows a CGI program to

remain active across multiple browser requests and maintain a session with that

browser client. This allows files to be left open, the state to be maintained, and

long running database transactions to be committed or rolled-back based on

end-user input. The AS/400 CGI program must be written using named activation

groups which allows the program to remain active after returning to the server.

The CGI program notifies the server it wants to remain persistent using the

″Accept-HTSession″CGI header as the first header it returns. This header defines

the session ID associated with this instance of the CGI program and is not returned

to the browser. Subsequent URL requeststo this program must contain the session

ID as the first parameter after the program name. The server uses this ID to route

the request to that specific instance of the CGI program. The CGI program should

regenerate this session ID for each request. It is strongly recommended that you

use Secure Sockets Layer (SSL) for persistent and secure business transaction

processing.

CGI programs can be built using named activation groups by specifying a name on

the ACTGRP parameter of the CRTPGM or CRTSRVPGMcommands. In doing this,

the initial call to the program within the job will still have the startup cost of

activating the program. However, an activation group is left active after the

program has exited normally.All storage associated with that program is still

allocated and in ″last-used″state. The program is not initializated when it is called

again. In addition, for the ILE C runtime, all settings are in ″last-used″state, such

as signal(), strtok(). The RCLACTGRP command is used to end a named activation

group. Use the DSPJOB OPTION(*ACTGRP) command to display all the activation

groups for the job. All ILE languages running on AS/400 can use this mechanism

to enable persistence for their CGI programs.

For additional information about activation groups see, ILE Concepts, SC41-5606

book.

This header specifies the session handle associated with this instance of the

Persistent CGI program. This session handle is used to route back subsequent

requests to that program and must be unique, or the server will not honor the

persistence request. A message is logged in the error log of the server.

Accept-HTSession = "Accept-HTSession" ":" handle

When the server receives this header, the CGI job servicing the request will be

reserved in a persistent state. Only requests coming in with that session handle in

the URL are routed back to that instance of the CGI program. The URL must be in

the following format: