The hang detection option for WebSphere Application Server
is turned on by default. You can configure a hang detection policy
to accommodate your applications and environment so that potential
hangs can be reported, providing earlier detection of failing servers.
When a hung thread is detected, WebSphere Application Server notifies
you so that you can troubleshoot the problem.
Before you begin
A common error in J2EE applications is a hung thread. A
hung thread can result from a simple software defect (such as an infinite
loop) or a more complex cause (for example, a resource deadlock).
System resources, such as CPU time, might be consumed by this hung
transaction when threads run unbounded code paths, such as when the
code is running in an infinite loop. Alternately, a system can become
unresponsive even though all resources are idle, as in a deadlock
scenario. Unless an end user or a monitoring tool reports the problem,
the system may remain in this degraded state indefinitely.
Using
the hang detection policy, you can specify a time that is too long
for a unit of work to complete. The thread monitor checks all managed
threads in the system (for example, Web container threads and object
request broker (ORB) threads) . Unmanaged threads, which are threads
created by applications, are not monitored. For more information read Hung threads in J2EE applications.
About this task
The thread hang detection option is enabled by default.
To adjust the hang detection policy values, or to disable hang detection
completely:
Procedure
- From the administrative console, click Servers > Application
Servers > server_name
- Under Server Infrastructure, click Administration > Custom
Properties
- Click New.
- Add the following properties:
Name: com.ibm.websphere.threadmonitor.interval
Value: The frequency (in seconds) at which managed threads in the selected
application server will be interrogated.
Default: 180 seconds (three minutes).
Name: com.ibm.websphere.threadmonitor.threshold
Value: The length of time (in seconds) in which a thread can be active
before it is considered hung. Any thread that is detected as
active for longer than this length of time is reported as hung.
Default: The default value is 600 seconds (ten minutes).
Name: com.ibm.websphere.threadmonitor.false.alarm.threshold
Value: The number of times (T) that false alarms can occur
before automatically increasing the threshold. It is possible that a
thread that is reported as hung eventually completes its work,
resulting in a false alarm. A large number of these events indicates
that the threshhold value is too small. The hang detection facility can
automatically respond to this situation: For every T false alarms, the
threshold T is increased by a factor of 1.5. Set the value to
zero (or less) to disable the automatic adjustment.
Default: 100
Name: com.ibm.websphere.threadmonitor.dump.java
Value: Set to true to cause a javacore to be created when a hung thread
is detected and a WSVR0605W message is printed. The threads
section of the javacore can be analyzed to determine what
the reported thread and other related threads are doing.
Default: False
To disable the hang detection option, set the com.ibm.websphere.threadmonitor.interval property
to less than or equal to zero.
- Click Apply.
- Click OK.
- Save the changes. Make
sure a file synchronization is performed before restarting the servers.
- Restart the Application Server for the changes to take
effect.