Controlling dynamic updates

There are three types of dynamic update that can be controlled through configuration: changing the server configuration; adding and removing applications; updating installed applications. For all deployed applications, you can configure whether application monitoring is enabled and how often to check for updates to applications. For the "dropins" directory, you can also configure the name and location of the directory and choose whether to deploy the applications that are in the directory.

About this task

By default, deployed applications are monitored for updates, and the updates are dynamically applied to the running application. This applies both to applications that are deployed through configuration entries, and those deployed from the "dropins" directory. You can change these default behaviors by setting the config and applicationMonitor elements in the server.xml configuration file. You can use a text editor to do this, or you can use the developer tools and select Configuration Admin Service or Application Monitor in the server configuration design view.

See also the descriptions of the config and applicationMonitor elements in Liberty profile: Configuration elements in the server.xml file.

The default settings for application monitoring are as follows:

<applicationMonitor updateTrigger="polled" pollingRate="500ms" 
                    dropins="dropins" dropinsEnabled="true"/>

Notes:

The updateTrigger property has three possible values:
polled

The runtime environment scans the server.xml file for changes using the timing interval specified by the monitorInterval property.

mbean

The runtime environment only looks for updates when prompted to do so through a call to an MBean. This is the mode that is used by the developer tools to update the server.xml file, unless you override it.

disabled

The updates are not dynamically applied.
When you specify the pollingRate property, you include the unit of time after the number:
- ms (milliseconds)
- s (seconds)
- m (minutes)
- h (hours)
The dropins property specifies the name of the directory used as the "dropins" directory.
The dropinsEnabled property is a boolean property that determines whether the applications in the "dropins" directory are deployed.

Procedure

Configure dynamic changes to the server configuration.
Changes to the server.xml file, or any files it includes, are detected by the runtime environment and applied to the active configuration. You can disable this behavior by setting the config element in the server.xml file:
```
<config updateTrigger="disabled"/>
```
Configure dynamic addition and removal of applications.
As described in Deploying applications to the Liberty profile, applications can be dynamically added to and removed from the server runtime environment through two mechanisms:
- By adding or removing application entries in the server.xml file.
  If you disable dynamic changes to the server configuration as described in the previous step, then adding or removing application entries has no effect on a running server. Your changes are only applied at the next server restart. The changes are picked up immediately, if you update application entries using the developer tools.
- By moving application files into and out of the "dropins" directory.
  This behavior can be controlled by setting the applicationMonitor element in the server.xml file. For example, to disable dynamic installation of applications from the "dropins" location, create an entry as follows:
```
<applicationMonitor dropinsEnabled="false"/>
```
Configure dynamic updates to installed applications.
By default, if you add, remove or modify any files within a deployed application, or you replace the whole application with an updated version, the previous version is automatically stopped and the new version is started. This process applies for any deployed application, whether the application is in the "dropins" directory or at a location defined in the server.xml file. You can control this behavior by setting the applicationMonitor element in the server.xml file. For example, to disable dynamic update of all applications, create an entry as follows:
```
<applicationMonitor updateTrigger="disabled"/>
```
Configure the name and location of the "dropins" directory.
By default, the "dropins" directory is ${server.config.dir}/dropins. You can change this by setting the applicationMonitor element in the server.xml file. For the location, you can use any known variable, or a property in the bootstrapping.properties file, or an absolute path, or a path relative to the server directory. For example, both the following settings point to the same location:
```
<applicationMonitor dropins="${server.config.dir}/applications" />
<applicationMonitor dropins="applications" />
```

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Last updated: Wednesday, 22 May 2013
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