Learn Health Management in IBM WebSphere Application Server
Introduction
Health Management is part of WebSphere Virtual Enterprise environment, which is integrated in WebSphere Application Server 8.5. WebSphere 8.5 is integrated with Operational policies, which leverage Health Policies. Health Management is policy-driven approach to monitor the WebSphere enterprise application server usage and able to respond to the problem areas before outage occurs. Health Management has two elements: health controller and health policies.
Reaction Mode
Health Policies include the health condition, which you want to monitor in your environment. It reacts when your defined conditions are not met. There are two reaction modes: automatic or supervised mode.
Automatic mode: System will take an action when health policy violation is detected. For ex, if you configure to monitor memory usage and would like to restart JVM when message usage is 85% then system will restart targeted JVM when JVM heap size reach at 85%.
Supervised mode: System will create runtime task when health policy violation is detected. This requires manual intervention for WebSphere administrator to approve or deny the runtime task action.
Health Conditions
Health Condition is the object or metrics you want to monitor in your environment. There are eight following predefined health condition available in WebSphere 8.5. You do have an option to create custom health condition.
Age-based condition- this condition will monitor the defined JVM and take action when reaches a configured age threshold. Ex, you can configure this condition to restart JVM if it’s running for 15 days. Acceptable value for this condition is in Days or Hours as shown below.
Excessive request timeout condition- this condition will take action when the request timeout percentage exceeds the defined value. Acceptable value is in percentage as shown below.
Excessive response time condition- this will monitor the time it takes for request to complete and take action if the time exceeds the defined threshold. Ex, you can configure this condition to take thread dump when response time for request is one minute. Acceptable value is in Milliseconds, Seconds and Minutes as shown below.
Memory condition: excessive memory usage- monitors the memory usage of JVM and take action if it exceeds the threshold value. Ex, you can configure this condition to take JVM heap dump and restart JVM when memory usage exceeds the threshold. Acceptable value for JVM heap size is in percentage and offending time period in Seconds and Minutes as shown below.
Memory condition: memory leak- this will look for memory leaks on JVM and take action. This got three detection levels.
1. Fast (more false alarms)
2. Standard (some false alarms)
3. Slow (fewer false alarms)
Storm drain condition- monitor significant drop in the average response time and take action like generate thread dump and restart JVM. This got two Detection level.
1. Standard (some false alarms)
2. Slow (fewer false alarms)
Workload condition- this condition will detect once a JVM has served a configured number of requests. Ex, you can configure to restart JVM once it serves 20000000 requests.
Garbage collection percentage condition- this monitor percentage of time spent in garbage collection for defined time period and take action once exceeds the threshold. Acceptable value is percentage and sampling time period as shown below.
Health Action
Health Action is the health policy action to be run once exceeds the configured threshold. There are seven following predefined health action available in WebSphere 8.5. You do have an option to create custom health action.
- Restart Server- to restart JVM
- Take thread dumps– to take thread dumps of JVM
- Take JVM heap dumps– to take JVM heap dumps
- Generate an SNMP trap- generate SNMP trap for troubleshooting
- Place server in maintenance mode- stop new client requests and serve only active session
- Place server in maintenance mode and break affinity – stop new and existing action session
- Place out of maintenance mode – ready to accept new requests
Health Policy Target
Health Policy or Action target can be JVM’s, Clusters, Dynamic clusters, on demand routers or Cells.
As next step, in next article I will talk about How to Create Health Policies
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