USER_AGENT

The USER_AGENT element sets a timeout to handle the user agent session.

Syntax

<USER_AGENT>seconds</USER_AGENT>
  1. seconds specifies the number of seconds to wait for a client request. If not specified, the default timeout is 300 seconds.

Child elements

There are no child elements.

Usage

Set this timeout to specify a number of seconds that the JGAS is to wait for a client request before assuming that the front-end has died or that there has been a network failure.

Important: The USER_AGENT is managed by the session. A session is started with the first application. If the first application starts several child applications, these applications become part of the session. The USER_AGENT does not time out while any one of these applications has activity.

To keep the application alive in case of user inactivity, the front-end regularly sends a ping request to the JGAS.

When the GAS sends the USER_AGENT timeout value to the Genero Browser Client at application start up, it divides it by 2. This helps ensure the GAS has time to receive at least one ping from the client if network traffic is experiencing very high latency. For example, where the USER_AGENT value is 300, the X-FourJs-Timeout response header contains 150:
X-FourJs-Timeout: 150

When does a session time out?

A session times out when the client has not sent a request to the JGAS before the USER_AGENT timeout expires. When this occurs, the JGAS assumes that the front-end client has died and sends an instruction to close the socket to the DVM, which causes the DVM to shut down.

If you have an OPTIONS ON CLOSE APPLICATION callback function set in order to try to release resources when a timeout occurs, this code is executed before the DVM shuts down. For more information on handling front-end termination, see the Front-end termination page in Genero Business Development Language User Guide.
Note: In case of normal application termination (using the application close button), the ON CLOSE APPLICATION callback is not called.

The USER_AGENT timeout proves to be particularly useful with applications running in the Genero web client. As with the other front-ends, when a user properly exits via the application close button, the DVM handling that application is properly shut down.

Common ways sessions time out

Application DVMs may stay running on your server until sessions time out under a variety of conditions, but it is most common in these scenarios:
  • If the user does not exit the application using the application close button, the session may stay alive. For instance, if a user closes the browser instead of using the application close button, the session may stay alive until the USER_AGENT time out is reached.
  • Another scenario is when a child application in the session is closed. The front-end sends a closing instruction, but that may in some circumstances, such as closing the browser tab, not reach the JGAS. In this case the child DVM keeps on running on your server until the main application is exited or has reached the USER_AGENT time out.

We recommend that you properly exit applications using the application close actions.

Usage example

<USER_AGENT>300</USER_AGENT>

In this example, the USER_AGENT timeout is set to 300 seconds.

Parent elements

This element is a child of one of the following elements: