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HPjmeter: User's Guide > Chapter 7 Using the Console
Using Alerts |
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The console provides a way for you to enable and disable alerts for specific events when monitoring an application. Enabled alerts can be deactivated and reactivated during the session as needed by using the Alert Controller. In addition, you can set thresholds in the Alert Controller to vary the sensitivity of the console to enabled alert conditions. When active alerts are triggered, a notification appears in the main pane of the console window. To view details about the application behavior that triggered the notification, double-click on the specific alert that you want to see. A metric window associated with the alert will open. See “Responding to Alerts” for information on specific alert notifications. The console displays an alert while the alert condition exists, and stops displaying when the alert condition no longer exists. A displayed alert may also stop displaying when HPjmeter recalculates the alert based on real-time information. The console displays a warning icon in the lower right corner of the window showing the current number of alerts detected. To open the Alert Controller, double-click on an Alerts counter row in the data tree. In the Controller, you can see all alerts available during that session. Because alert preferences are set at the beginning of a monitoring session, it is not necessary to use the Alert Controller to activate alerts.
You can use the Alert Controller in these ways: Deactivate or reactivate enabled alerts. To deactivate or reactivate alerts once a session has started, use the check box next to the alert name.
Set alert thresholds. You can use default settings or set values for enabled alerts. For each alert enabled, you can select a numerical threshold and a time constraint. The alert is triggered when the threshold is passed for the duration of the allotted time. For example, if you are setting values for Heap Usage Notification, and you choose ≥ 50 MB and a time constraint of 60 seconds, the alert will trigger when the heap usage in the application exceeds the 50 MB threshold for at least 60 seconds. A notification appears in the console main panel for as long as the threshold is crossed, periodically updating to show the current value of the heap usage. New values for alerts are applied immediately when you select Apply. From the Alert Controller, select the Alert Log button to see a history of alerts noted during the monitoring session. Change the alert log capacity. From the Alert Log window, click the “Select Log Capacity” icon to open the log capacity window. Change the value as desired for number of lines to include in the log. Double-click on individual alerts listed in the data tree in the main console window. This will open a window containing metric information for that particular alert. The following information is specific for each alert type. HPjmeter detects threads that terminate abnormally because of an uncaught exception. When HPjmeter detects that a thread terminated abnormally, the console main window displays an Abnormal Thread Termination Alert. Double-clicking on the alert in the main window displays the uncaught exception window. The window shows:
You can use this information to debug the cause of the exception. For example, each row in the Abnormal Thread Termination window represents a thread in the Thread Histogram window. You can open the Thread Histogram metric, and notice that when a thread terminates, the associated bar in the Thread Histogram display is shorter than the others. Note that the thread histogram does not distinguish between threads that terminate normally or abnormally. Symptoms that an application might show if it has abnormally terminating threads include:
See also: These statistics are derived from more than one metric. The Uncaught Exception Statistics display shows you:
The window shows events in a hierarchical tree.
The results are cumulative over the life time of the session. See also: HPjmeter detects when a method is repeatedly compiled. Double-click on the Excessive Compilation alert to display the metrics for excessive method compilation. See also: Identifying Excessive Method Compilation . HPjmeter detects memory leaks automatically and reports an alert before a crash occurs. Double-click on the alert to open the Heap Monitor display. The heuristic algorithms for alert triggers are tuned for server-oriented applications. The alerts are based on heuristic algorithms and are not offered with 100 percent certainty. Fluctuations in the application load may cause a transient increase in memory usage. To confirm the leak, monitor the application for one hour or longer; then review the Garbage Collections metrics. See also: It can be useful to change the heap usage threshold in order to observe the heap structure at the selected usage point. You can also set this threshold to notify you when heap usage exceeds your maximum or minimum expectations for the application. For example, if you expect that your application should never consume more than 100 MB of heap for a target period of time, set the threshold fields for heap size and time sustained, and check that the alert is enabled. If the set values are exceeded, an alert is generated and recorded in the alert log. An alert notice is posted on the console. Double-click on the alert to display the Heap Monitor visualizer. In this visualizer, you can see the memory allocated to the heap compared to usage over time, and including indicators for garbage collection events and their duration. See also: HPjmeter detects potential Java collection memory leaks and identifies the source-file line of the leak. The console main window displays a Memory Leak Locations Alert when a Java collection class memory leak is detected. Double-clicking on the alert displays the Memory Leak Locations Window. The window shows:
After some time, the alert icon may disappear if:
HPjmeter has removed the alert icon when it removes all the leak nodes and no new memory leak detected. See also: Enable this alert to track target levels of process CPU utilization. Significant variance from target levels may indicate the presence of performance bottlenecks caused by thread starvation due to the application using all available CPU resources or due to overuse by processes other than your application. As an example, assume that you have a 4-way machine, and you expect your Java application to consume at least 100% of 1 CPU. When running this application, enable this alert, and set a usage percentage that reflects the expected consumption for a designated period of time (equal to or greater than 25%). If that value is exceeded during the monitoring session, a notification is generated and recorded in the alert log. Conversely, if you expect that your application will always use at least 100% of 1 CPU, set the operator at less than or equal to 25% to trigger a notification that the application is not consuming resources as expected. When the set threshold is met, an alert notice is posted on the console. Double-click on the alert to display the Percent CPU Utilization visualizer. In this visualizer, you can see system and process CPU usage during the period of the monitoring session plotted against the known resources of the server. For more information, see also: Enable this alert to track target levels of system-level CPU usage. Significant variance from target levels may indicate over- or under-utilization of system resources. As an example, assume that you have a 4-way machine, and you expect CPU usage to consume no more than 100% of 3 CPU. When monitoring, enable this alert, and set a usage percentage that reflects the expected consumption for a designated period of time (equal to or greater than 75%). If that value is equaled or exceeded during the monitoring session, a notification is generated and recorded in the alert log. Conversely, if you expect that your system CPU usage will always be more than 100% of 3 CPU, set the operator at less than or equal to 75% to trigger a notification that the system usage is less than expected. When the set threshold is met, an alert notice is posted on the console. Double-click on the alert to display the Percent CPU Utilization visualizer. In this visualizer, you can see system and process CPU usage during the period of the monitoring session plotted against the known resources of the server. For more information, see also: HPjmeter reports the possibility that two or more threads are attempting to acquire Java locks that have been acquired already by this set of threads. Double-click the alert to display the thread histogram window. This allows you to determine which threads are deadlocked. Deadlocked threads represent a multi-threaded program error. An application experiencing a deadlock may not crash, but it is unresponsive to requests. If the alert persists, it suggests a problem in the application logic that will need to be addressed by developers. See also: |
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