Health management
With health management, the system can take a policy-driven approach to monitoring the application server environment and take action when certain criteria are discovered.
Health monitoring and management subsystem
The health management subsystem continuously monitors the state of servers and the work that is performed by the servers in your environment. The health management subsystem consists of two main elements:
- health controller
- health policies
The health controller is the autonomic manager that controls the health monitoring and management subsystem, and acts on your health policies to ensure certain conditions exist. The health controller is a distributed resource that is managed by the high availability manager. The health controller exists within all of the node agent and deployment manager processes. The health controller is active in one of these processes. If the active process fails, the health controller can become active on another node agent or deployment manager process.
The health controller runs on a control cycle. The control cycle length defines the amount of time that passes between the checks that the health controller runs on the environment. After the control cycle ends, the health controller checks the environment and generates runtime tasks to resolve any breaches in the health conditions.
You can disable or enable health management using the health controller, while still having multiple health policies defined on the system. You can also apply limits to the frequency that the server restarts or prohibit restarts during certain periods.
Health policies define the health conditions to monitor in your environment and the health actions to take if these conditions are not met.
The health management subsystem functions when WebSphere Virtual Enterprise is in automatic or supervised operating mode. When the reaction mode on the policy is set to automatic, the health management system takes action when a health policy violation is detected. In supervised mode, the health management system creates a runtime task that proposes one or more reactions. The system administrator can approve or deny the proposed actions.
Health conditions
Health conditions define the variables to monitor in your environment. Several categories of health policy conditions exist. The following list defines the predefined health conditions:
- Excessive memory consumption, which can indicate a memory leak
- Excessive response time, which can indicate that the server is in an endless loop
- Excessive request timeout, which can indicate that the server is in an endless loop
- The volume of work performed by a server
- Storm drain detection, which relies on change point detection on given time series data
- The age of the server
With these predefined health policy conditions, actions have been taken to optimize the distribution of the needed data and minimize the impact of monitoring and enforcing the health policy on your overall environment.
You can also define custom conditions within your health policy. Use a custom condition when the predefined health conditions do not fit your needs. You define custom conditions as a subexpression that is tested against metrics in your environment. When you define a custom condition, consider the cost of collecting the data, analyzing the data, and if needed, enforcing the health policy. This cost can increase depending on the amount of traffic and number of servers in your network, so analyze the performance of your custom health conditions before you move them into production.
Health actions
Health actions define the process to use when a health condition is not met. Depending on the conditions that you define, the actions can vary.
Health Action WebSphere Application Server or WebSphere Virtual Enterprise servers Other Middleware Servers Restart server Supported Supported Take thread dumps Supported for servers that are running on the IBM Software Development Kit Not supported Take Java virtual machine (JVM) heap dumps Supported for servers that are running on the IBM Software Development Kit Not supported Put server into maintenance mode Supported Supported Put server into maintenance mode and break HTTP and SIP request affinity to the server Supported Supported Take server out of maintenance mode Supported Supported You can also define a custom action, which is an executable file that runs when the health condition breaches. You must define custom actions before you create the health policy that contains the custom actions.
Health policy targets
Health policy targets can be a single server, each of the servers in a cluster or dynamic cluster, the on demand router (ODR), or each of the servers in a cell. You can define multiple health policies to monitor the same set of servers.
If you are using a predefined policy, then the support of the policy varies depending on the server type. Other middleware servers do not support all of the policy types. The following table summarizes the health policy support, by server type:
Predefined Health Policy WebSphere Application Server or WebSphereWebSphere Virtual Enterprise servers Other Middleware Servers Age-based policy Supported Supported Workload policy Supported Supported Memory leak detection Supported Not supported Excessive memory usage Supported Supported for WebSphere Application Server Community Edition servers. Not supported for other middleware server types. Excessive request timeout Supported Supported for other middleware servers to which the ODR routes requests. Excessive response time Supported Supported Storm drain detection Supported Supported
Default health policies
Default health policies are a set of predefined, supervised mode, cell-level policies that are installed with WebSphere Virtual Enterprise. You can modify the default policies for your environment, or delete the default health policies. Because the default health policies monitor each server in supervised mode, you can use these policies to prevent health problems. You can define policies with more detailed settings or automated mode operation for particular servers or collections of servers in addition to the default policies. Five default cell-wide health policies are created during installation. The following default health policies correspond to the appropriate policy type:
- Default memory leak:
Default standard detection level.
The default memory leak health policy uses the performance advisor functionality, so the performance advisor is enabled when this policy is enabled. To disable the performance advisor, remove this health policy or narrow the membership of the health policy. To preserve the health policy for future use, consider keeping the default memory leak policy, but removing all of the members. To change the members, click Operational policies > Health policies > Default_Memory_Leak.
You can edit the health policy memberships by adding and removing specific members from the policy.
- Default excessive memory usage:
Set to 95 percent of the JVM heap size for 15 minutes
- Default excessive request timeout:
Set for 5 percent of the requests timing out
- Default excessive response time:
Set to 120 seconds
- Default storm drain:
Default standard detection level
To view the recommendations that are made by the default health policies and to take actions on these recommendations, click...
System administration | Task management | Runtime tasks
Related concepts
Excessive request timeout health policy target timeout value
Related tasks
Configure health management
Create health policies
Set maintenance mode
Create health policy custom actions
Manage runtime tasks