Weblogic 4.5.1 easy to deadlock

Question

I have downloaded and begun to evaluate WL.
I must not understand some configuration settings because I have found
it easy to deadlock the server.
I have set weblogic.system.executeThreadCount=30
I have a benchmark.jsp file where the java code in the jsp page creates
on t3 connection to the local host and makes use of that t3 connection
to open a jdbc connection from a weblogic jdbc connection pool that I
set up.
I have a test http client that can simulataneously open N connections to
an http server and fetch pages. The number of N connections is
configurable.
I have found that as the number of connections opened in parallel
approaches 30 (executeThreadCount value), WL seems to deadlock. My
guess is that 30 execute threads are allocated to http/jsp requests,
each of these 30 threads is now locked waiting for a t3 connection,
which will never happen because the execute thread pool is empty. All
of the executeThreads are blocked waiting for a t3 connection that
requires an executeThread of its own.
Does my analysis make sense? Is it possible to change some
weblogic.properties to avoid this scenario? I don't think that simply
increasing executeThread count is the answer since it only changes the
threshold. I don't want a threshold at which my system just stops
responding.
I thought that perhaps using a different webserver would alleviate the
problem of wasting the executeThread pool on http connections. But then
I thought that there would be a connection for each servlet engine
connection so the problem is no different.
Thanks,
Kevin

Answer 1

Joseph,
You were exactly right. Problem solved.
Thanks,
Kevin
Joseph Weinstein wrote:
>
Hi Kevin. The docs are being fixed up to remove T3 connecting from the
forefront. This was from when most clients were external JVMs. You should
never make a JDBC-T3 connection from a serverside class. That makes
a socket connection out of, and back into the server, just to get to the pool,
and if the latter has to call a DriverManager call, you will deadlock because
DriverManager calls like getCOnnection or even println() are class synchronized.
Look to the documentation for the pool driver for accessing pool connections
from serverside classes such as servlets.
Joe
Kevin McEntee wrote:
I have downloaded and begun to evaluate WL.
I must not understand some configuration settings because I have found
it easy to deadlock the server.
I have set weblogic.system.executeThreadCount=30
I have a benchmark.jsp file where the java code in the jsp page creates
on t3 connection to the local host and makes use of that t3 connection
to open a jdbc connection from a weblogic jdbc connection pool that I
set up.
I have a test http client that can simulataneously open N connections to
an http server and fetch pages. The number of N connections is
configurable.
I have found that as the number of connections opened in parallel
approaches 30 (executeThreadCount value), WL seems to deadlock. My
guess is that 30 execute threads are allocated to http/jsp requests,
each of these 30 threads is now locked waiting for a t3 connection,
which will never happen because the execute thread pool is empty. All
of the executeThreads are blocked waiting for a t3 connection that
requires an executeThread of its own.
Does my analysis make sense? Is it possible to change some
weblogic.properties to avoid this scenario? I don't think that simply
increasing executeThread count is the answer since it only changes the
threshold. I don't want a threshold at which my system just stops
responding.
I thought that perhaps using a different webserver would alleviate the
problem of wasting the executeThread pool on http connections. But then
I thought that there would be a connection for each servlet engine
connection so the problem is no different.
Thanks,
Kevin--
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