Monitoring and tuning the application placement controller

The application placement controller is designed to work with the default settings. However, there can be times when fine tuning the application placement controller becomes necessary to ensure the best results.

Before you begin

Before you can tune application placement, you need to have dynamic application placement running. For more information about enabling application placement, read about configuring dynamic application placement

Depending on your administrative role, you are allowed the following specific privileges when you are configuring the application placement controller:

Monitor: Can view the information.
Operator: Can view the information on the configuration tab. Can change the settings on the runtime tab.
Configurator: Can change the configuration but not the runtime settings.
Administrator: Has all privileges.

About this task

You might tune the application placement controller for the following reasons:

To adjust the amount of time before runtime tasks expire
To adjust the amount of time that passes before starting or stopping a server is considered a failure
To adjust the amount of time between placement changes for applications

Procedure

In the administrative console, click Operational policies > Autonomic managers > Application placement controller.
Determine whether you want to modify the persistent settings in the configuration tab, which are permanent between stops and starts of the application placement controller, or test runtime settings in the runtime tab, which last for the life of the application placement controller.
You can choose to modify the runtime settings and then find those settings are actually what you want to use as permanent settings. You can make runtime settings persistent settings by clicking Save to repository.
Modify the application placement controller settings, as needed.
The table following these steps contains the general configuration settings.
Define custom properties to change placement behavior.
You can specify the reservedMemoryFixed and reservedMemoryPercent custom properties to define how much node memory to reserve for processes that are not related to WebSphere® Application Server or Intelligent Management.
For information about custom properties that you can set on the application placement controller, read about application placement custom properties.
Click Apply or OK.
Save your changes.
Iterate and modify the settings as needed.
Make changes until you discover the best possible configuration for your environment.

Results

Table 1. General configuration settings
Setting	Description
Enable	Enables or disables the application placement controller. If you disable the application placement controller, you are disabling all autonomic operations for the dynamic clusters. After the placement controller is disabled, no dynamic changes occur with regard to the size and placement of applications on the dynamic cluster. This action is equivalent to turning all dynamic clusters to static clusters.
Approval timeout	Controls how long the runtime task sits in the queue awaiting action before it expires automatically. Acceptable time values are 1 to 60 minutes. This setting is particular to the supervised operating mode. When the operating environment is set to run in supervised mode, the application placement controller creates tasks, but must wait for approval from the system administrator before making changes. The application placement controller treats runtime tasks that are timed out as user-rejected tasks.
Server operation timeout	Represents the amount of time, in minutes, that the application placement controller waits for a start or stop operation to complete before the operation is considered a failure. Set this value to the predicted worst case time to start or stop a server. Acceptable values are between 1 to 60 minutes. If a server fails to start before the timeout, the server is put into maintenance mode. The application placement controller avoids trying to start that server again until you manually fix the start issue and manually start the server. When the server starts, the application placement controller detects that the server has started. Servers are not automatically placed in maintenance mode when the servers fail to start before the server operation timeout. Instead, a runtime task is generated a when the server fails to start. The application placement controller does not attempt to start this server again until the server is successfully started manually. When you successfully start the server manually, the application placement controller receives a notification that the server has started. If you want the servers to be put into maintenance mode, you can set the maintenanceModeOnOperationFail custom property on the application placement controller. If you want to take servers out of maintenance mode after starting successfully, you can specify the unsetMaintenanceModeAfterStart custom property on the application placement controller. For information about custom properties that you can set on the application placement controller, read about application placement custom properties.
Minimum time between placement change	Specifies the amount of time that the application placement controller waits before initiating a new batch of changes. The application placement controller might wait for a batch of changes after completing previous changes, or encountering a timeout. Acceptable values can range from 1 minute to 24 hours. When setting this value, consider the overhead that is associated with starting and stopping servers. Starting or stopping servers can take several minutes and might introduce an additional load to the nodes. If you allow the placement controllers to readjust application placement too often, the added overhead negates the increased performance gains that can be earned by readjusting the size of dynamic clusters. For example, if a server takes one minute to start, and the setting for the minimum time between placement changes is 20 minutes, then placement changes have a performance impact of approximately 5%. Set this value at least 20 to 30 times larger than the time necessary to start a server. A value greater than several hours prevents application placement changes from happening more than once a day. If you believe that traffic load and application demands adjust several times during a day, you might want to allow placement changes to occur more frequently.

The application placement controller is tuned for its best performance.