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Intelligent Management: application placement frequently asked questions


Where is the application placement controller running?

To find where the application placement controller is running, we can use the administrative console or scripting. To check the location in the administrative console, click...

We can also run the checkPlacementLocation.jacl script to display the server on which the application placement controller is running.


When does the application placement controller start a server?

The application placement controller starts servers for the following reasons:

For a view of what is running in view of the application placement controller, see the SystemOut.log messages.


When does the application placement controller stop a server?

The application placement controller stops a server for the following reasons:


Why did the application placement controller not start a server?

The application placement controller does not display that the server is started for one of the following reasons:

View failed start information

Remember: The failed start list is not persisted when the application placement controller restarts or moves between nodes.

We can view failed start information with one of the following options:


Why did the application placement controller start more servers than I expected?

More servers can start than expected when network or communication issues prevent the application placement controller from receiving confirmation that a server started. When the application placement controller does not receive confirmation, it might start an additional server.


Why did the application placement controller submit multiple tasks for starting the same server?

The reason for this behaviour can be the fact that the application placement controller runs on multiple servers. This scenario often occurs in mixed topologies, where a WebSphere Application Server Version 8.5 cell also contains a WebSphere Virtual Enterprise Version 6.1.x node. The application placement controller runs on both nodes: the WAS v8.5 node and the WebSphere Virtual Enterprise Version 6.1.x node. WAS Version 8.5 and WebSphere Virtual Enterprise Version 6.1.x nodes use different high availability solutions by default. Therefore, multiple application placement controllers are running. To correct the issue, run the useBBSON.py script on the deployment manager, and restart the cell. The script sets the cell custom properties to ensure that the same high availability solution is used throughout the cell, and that only one application placement controller is started.


How do I know when the application placement controller has completed or will complete an action?

We can check the actions of the application placement controller with runtime tasks. To view the runtime tasks, click...

The list of runtime tasks includes tasks that the application placement controller is completing, and confirmation that changes were made. Each runtime task has a status of succeeded, failed, or unknown. An unknown status means that there was no confirmation either way whether the task was successful.


How does the application placement controller work with VMware? Which hardware virtualization environments are supported?

For more information about how the application placement controller works with VMware and other hardware virtualization environments, read about virtualization and Intelligent Management and supported server virtualization environments.


How can I start or stop a server without interfering with the application placement controller?

If we start or stop a server while the dynamic cluster is in automatic mode, the application placement controller might decide to change your actions. To avoid interfering with the application placement controller when we start or stop a server, put the dynamic cluster into manual mode before starting or stop a server.


In a heterogeneous system (mixed hardware or operating systems), how does the application placement controller pick where to start a server?

The membership policy for a dynamic cluster defines the eligible nodes on which servers can start. From this set of nodes, the application placement controller selects a node on which to start a server by considering system constraints such as available processor and memory capacity. The application placement controller does not determine the server placement based on operating systems.


When my dynamic cluster is under load, when does the application placement controller start another server?

The application placement controller works with the autonomic request flow manager (ARFM) and defined service policies to determine when to start servers. Service policies set the performance and priority maximums for applications and guide the autonomic controllers in traffic shaping and capacity provisioning decisions. Service policy goals indirectly influence the actions that are taken by the application placement controller. The application placement controller provisions more servers based on information from the ARFM about how much capacity is required for the number of concurrent requests that are being serviced by the ARFM queues. This number is determined based on how much capacity each request uses when it is serviced and how many concurrent requests ARFM determines is appropriate. The number of concurrent requests is based on application priority, goal, and so on.

The performance goals defined by service policies are not guarantees. Intelligent Management cannot make the application respond faster than its limit. In addition, more capacity is not provisioned if enough capacity is already provisioned to meet the demand, even if the service policy goal is being breached. Intelligent Management can prevent unrealistic service policy goals from introducing instability into the environment.


How does the application placement controller determine the maximum heap size of my server?

We can change the heap size of the server in the dynamic cluster template. See modifying the JVM heap size.


Why are the dynamic cluster members not inheriting properties from the template?

We must save dynamic clusters to the master repository before changing the server template. If we have dynamic cluster members that do not inherit the properties from the template, the server template probably incurred changes in an unsaved workspace. To fix this issue, delete the dynamic cluster, then recreate it.

Save our changes to the master repository. We can ensure that our changes are saved to the master repository after clicking Finish, by clicking Save in the message window. Click Save again in the Save to master monfiguration window. Click Synchronize changes with nodes.


Why does my dynamic cluster have too few active servers?

If we encounter problems where not enough servers are running in the dynamic cluster, try the following actions:


In a dynamic cluster environment, why does the application placement controller fail to distribute available servers across nodes?

Dynamic application placement is based on load distribution, service policy, and available resources. When reducing the maximum number of application instances in a dynamic cluster, the application placement controller stops servers on nodes with highest workload until the number of servers is reduced to the set maximum value. If all the nodes are available, the application placement controller selects the first node in the list, and continues with the next node in the list until the maximum number is met.

When reducing the maximum number of application instances in multiple dynamic clusters running on the same nodes, the same process applies: the application placement controller stops servers in each dynamic cluster until the number of servers meets the set maximum for each dynamic cluster. Because all the servers in each dynamic cluster are running on the same nodes, the node selection order for stopping servers is the same for each dynamic cluster.

If at least one node is under load, the application placement controller initiates a more distributed placement solution.


Related:

  • Virtualization and Intelligent Management
  • Configure dynamic application placement
  • Modify the JVM heap size
  • Intelligent Management: supported server virtualization environments
  • Intelligent Management: administrative roles and privileges
  • checkPlacementLocation.jacl script
  • Intelligent Management: application placement custom properties