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 Java Platform, Enterprise Edition (Java EE) 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 Java Platform, Enterprise Edition 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.
- newfeatAdd 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 |
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 |
Name |
com.ibm.websphere.threadmonitor.dump.stack |
Value |
Set to true to cause a stack trace to be printed when a hung
thread is detected and a WSVR0605W message is printed. |
Default |
true |
![[Updated in July 2011]](../../deltaend.gif)
jul2011
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.