What
is STUCK thread?
How
to deal with STUCK thread?
What
is HOGGING thread?
How
Weblogic determine a thread to
declare as Hogging?
What
is a STUCK thread?
We know that a STUCK thread is a thread which is processing a
request for more than maximum
time defined for a thread to complete the request which is default
600 and can be configured from admin console.
Based on different technical circumstances like due to some intermittent
issues with network, database, application server
etc a STUCK can be release after
some time, but most of the time is certain thread
or threads
declared as STUCK then there would be some problem either temporary
or permanent which need some fix.
How
to deal with STUCK thread?
As of now there is no way to deal with a STUCK thread like,
sometime end users ask if there any way to kill STUCK thread. No, there is no
way to deal with STUCK thread.
To deal with STUCK thread –
·
Take multiple thread dumps immediately.
·
Review thread dumps or from console (managed
server > monitoring > threads) Where it exactly got stuck?
·
See how many threads got stuck?
·
If the stuck thread count is increasing or constant?
·
If constant
then if got stuck on same
area (application code
etc ) or
at different places ?
·
If getting increase then there would be some serious problem and
you have to do a quick health check of you application
server, database and other integrated technologies wherever your application reaching
like ldap server for authentication, some other API’s or web services etc ,
and in parallel review thread dumps for STUCK threads and share same with your
developers to analyze quickly.
·
If you have one, two or few constant STUCK threads and it’s not increasing
then you can monitor it for some more time to check if they get clear or not,
if not
then to clear them you have only option to restart your managed
server(s), and its better to restart and clear them before they make further
any impact.
What
is Hogging thread?
I am sure if you are going to read this post
then you must aware about what is hogging thread. Ok, let me define
it again in a single line, “I hogging thread is a thread which is taking more
than usual time to complete the request and can be declared as STUCK”.
How
Weblogic determine a thread to
declare as Hogging?
As we know a
thread declared as STUCK if it runs over 600 secs (default
configuration which you can increase or decrease from admin console).
Now, How
Weblogic determines a thread to
declare as Hogging? ok ,
here is the logic which
I had learn from
some of the Oracle internal portal note.
1.
There is an internal WebLogic polar which runs every 2 secs (by
default 2 secs and
can be alter )
2.
It checks for the number of requests completed in last
two minutes
3.
Then it check how
much times each took to complete
4.
Then it takes the average time of all completed request (completed
in last 2 sec )
5.
Then multiply average time with 7, and the value came consider as
“usual time to complete the request”
6.
Now weblogic check each
current executed thread in last 2 secs and
compare with above average time, if for any of the thread
it’s above this value then that thread will declare as Hogged thread.
For
example –
1.
At a particular moment, total number of completed requests
in last two seconds – 4
2.
Total time took by all 4 requests – 16 secs
3.
Req1 took – 5 secs ,
Req2 took – 3 secs ,
Req3 took – 7 secs ,
Req4 took – 1 sec
4.
Average time = 16/4 = 4 secs
5.
7*4 = 28 secs
6.
Now weblogic check all executed threads to see which taking
more than 28 secs,
if any then that thread( s) declared as Hogged Thread.
Only
the thing you can change with respect to hogging threads configuration is Polar
time (Stuck Thread Timer
Interval parameter) which is 2 secs by default. You can change this polar value
to some different value like 4 secs if
you want polar to run in every 4 secs instead of 2 secs.
