Application hanging on Tomcat 7.0.54

Discussion:

Louis Zipes

2018-09-26 18:42:08 UTC

Hi all,
Tomcat 7.0.54 running on Windows 2012

We are running a third party application on Tomcat and today we have intermittently run in issues where the application stops working. The big changes in our system is that we have added more end users and we are at year end so of course everyone is hitting the system hard. Even if we force a log out of all users and stop all background jobs then the application doesn't recover.

We see no active sessions on the database (our application is connecting to an Oracle database) and I see no clear error messages in either our third party application logs or the Tomcat logs (ex. OutofMemory). When we go to the Windows Task Manager we did not see the machine's Memory max'd out but admittedly I didn't look at the Java session to see if was reaching its Heap Max. The only thing that we noticed was that TCP connections went down right after the restart. I did open up Jconsole under Java and I did force a garbage collection but that didn't seem to help.

We do have an Oracle Grid Control and we did get an alert in regards to Metric: [HTTP Transaction] Perceived Time per Page going past thresholds but not sure if that was just an old alert with and old range that was set up a long time ago or is a really valid clue. Since this is PRD we had to get it back up and running so all I did was increase the Tomcat Xmx Heap size and restarted. I'm not really confident that is the solution since as mentioned you tend to see a clear out of memory error if it was too small.

So a few questions:

1) Does this sound like a known issue with this earlier version of Tomcat?

2) Should I turn up any logging on Tomcat and if so which ones?

3) We didn't do a JSTACK dump while it was happening. Would that have been useful?

4) Do we need to play around with MaxThreads and/or MaxConnections. We do have maxThreads in our server.mxl but in DEV when we turned it down to a value = 5 hoping to overwhelm it nothing bad happened.

Once again, we are limited to what we could do and collect since it was PRD and we needed to restart it. We restarted the Tomcat service and everything is processing fine for right now. I will note that that we did have that bad Windows patch that prevented it from stopping and starting cleanly (https://stackoverflow.com/questions/51498291/tomcat-lockup-on-shutdown) but we have taken the break fix patch and the daily restarts seem to be fine since then.

Any comments/suggestions are appreciated!

Thanks, Louis

LOUIS ZIPES
SOFTWARE DEVELOPER ANALYST IV
O: 781-418-3257
***@keurig.com<mailto:***@keurig.com>
Keurig Dr Pepper
Visit us at www.KeurigDrPepper.com<http://www.keurigdrpepper.com/>

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Christopher Schultz

2018-09-26 19:46:00 UTC

Permalink

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Louis,

No.

2) Should I turn up any logging on Tomcat and if so which
ones?

Not yet.

3) We didn't do a JSTACK dump while it was happening. Would that have been useful?

Absolutely.

4) Do we need to play around with MaxThreads and/or
MaxConnections. We do have maxThreads in our server.mxl but in DEV
when we turned it down to a value = 5 hoping to overwhelm it
nothing bad happened.

Don't change anything, yet.

Once again, we are limited to what we could do and collect since it
was PRD and we needed to restart it. We restarted the Tomcat
service and everything is processing fine for right now. I will
note that that we did have that bad Windows patch that prevented it
from stopping and starting cleanly
(https://stackoverflow.com/questions/51498291/tomcat-lockup-on-shutdow

but we have taken the break fix patch and the daily restarts seem
to be fine since then.
Any comments/suggestions are appreciated!

Your most likely problem is database connection pool mismanagement:
connections aren't properly released and the pool empties. All threads
are left waiting on available database connections which will never be
replenished.

- -chris
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Louis Zipes

2018-09-26 19:56:43 UTC

Permalink

Problem just re-occurred and so I was able to at least get a JSTACK (I assume it was Tomcat since it was the Java using the most memory on the machine). Here is the reoccurring message. I get more hits on but haven't dug through all of the Google hits yet (due to multi-tasking) so apologies up front if there is a simple answer to this.

"Event_Manager_1413" daemon prio=6 tid=0x0000000024856000 nid=0x40c4 waiting on condition [0x0000000042dae000]
java.lang.Thread.State: TIMED_WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000005ab45f7b8> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.parkNanos(Unknown Source)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(Unknown Source)
at java.util.concurrent.LinkedBlockingQueue.poll(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.getTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

Locked ownable synchronizers:
- None

Post by Louis Zipes
Any comments/suggestions are appreciated!

Your most likely problem is database connection pool mismanagement:
connections aren't properly released and the pool empties. All threads
are left waiting on available database connections which will never be
replenished.

I'm using the ojdbc6.jar if that is what you are referring to or is there a better setting somewhere.

-----Original Message-----
From: Christopher Schultz [mailto:***@christopherschultz.net]
Sent: Wednesday, September 26, 2018 3:46 PM
To: ***@tomcat.apache.org
Subject: Re: Application hanging on Tomcat 7.0.54

- - - external message, proceed with caution - - -

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Louis,

Post by Louis Zipes
Hi all, Tomcat 7.0.54 running on Windows 2012
We are running a third party application on Tomcat and today we
have intermittently run in issues where the application stops
working. The big changes in our system is that we have added more
end users and we are at year end so of course everyone is hitting
the system hard. Even if we force a log out of all users and stop
all background jobs then the application doesn't recover.
We see no active sessions on the database (our application is
connecting to an Oracle database) and I see no clear error messages
in either our third party application logs or the Tomcat logs (ex.
OutofMemory). When we go to the Windows Task Manager we did not
see the machine's Memory max'd out but admittedly I didn't look at
the Java session to see if was reaching its Heap Max. The only
thing that we noticed was that TCP connections went down right
after the restart. I did open up Jconsole under Java and I did
force a garbage collection but that didn't seem to help.
We do have an Oracle Grid Control and we did get an alert in
regards to Metric: [HTTP Transaction] Perceived Time per Page going
past thresholds but not sure if that was just an old alert with and
old range that was set up a long time ago or is a really valid
clue. Since this is PRD we had to get it back up and running so
all I did was increase the Tomcat Xmx Heap size and restarted. I'm
not really confident that is the solution since as mentioned you
tend to see a clear out of memory error if it was too small.
1) Does this sound like a known issue with this earlier version of Tomcat?

No.

Post by Louis Zipes
2) Should I turn up any logging on Tomcat and if so which
ones?

Not yet.

Post by Louis Zipes
3) We didn't do a JSTACK dump while it was happening. Would that have been useful?

Absolutely.

Post by Louis Zipes
4) Do we need to play around with MaxThreads and/or
MaxConnections. We do have maxThreads in our server.mxl but in DEV
when we turned it down to a value = 5 hoping to overwhelm it
nothing bad happened.

Don't change anything, yet.

Post by Louis Zipes
Once again, we are limited to what we could do and collect since it
was PRD and we needed to restart it. We restarted the Tomcat
service and everything is processing fine for right now. I will
note that that we did have that bad Windows patch that prevented it
from stopping and starting cleanly
(https://stackoverflow.com/questions/51498291/tomcat-lockup-on-shutdow

Post by Louis Zipes
but we have taken the break fix patch and the daily restarts seem
to be fine since then.
Any comments/suggestions are appreciated!

Christopher Schultz

2018-09-26 23:29:32 UTC

Permalink

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Louis,

at java.util.concurrent.locks.LockSupport.parkNanos(Unknown Source)

Post by Louis Zipes
at
java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.

awaitNanos(Unknown

Post by Louis Zipes
Source) at java.util.concurrent.LinkedBlockingQueue.poll(Unknown
Source) at java.util.concurrent.ThreadPoolExecutor.getTask(Unknown
Source) at
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown
Source) at java.lang.Thread.run(Unknown Source)

This thread is waiting for a task, and is essentially idle. You will
have many of these on a non-busy system.

What are the other threads doing?

Post by Louis Zipes
Locked ownable synchronizers: - None

Post by Louis Zipes
Any comments/suggestions are appreciated!

Your most likely problem is database connection pool
mismanagement: connections aren't properly released and the pool
empties. All threads are left waiting on available database
connections which will never be replenished.
I'm using the ojdbc6.jar if that is what you are referring to or is
there a better setting somewhere.

ODBC? What is your database?

- -chris

Post by Louis Zipes
-----Original Message----- From: Christopher Schultz
Application hanging on Tomcat 7.0.54
- - - external message, proceed with caution - - -
Louis,

Post by Louis Zipes
Hi all, Tomcat 7.0.54 running on Windows 2012
We are running a third party application on Tomcat and today we
have intermittently run in issues where the application stops
working. The big changes in our system is that we have added
more end users and we are at year end so of course everyone is
hitting the system hard. Even if we force a log out of all users
and stop all background jobs then the application doesn't
recover.
We see no active sessions on the database (our application is
connecting to an Oracle database) and I see no clear error
messages in either our third party application logs or the Tomcat
logs (ex. OutofMemory). When we go to the Windows Task Manager
we did not see the machine's Memory max'd out but admittedly I
didn't look at the Java session to see if was reaching its Heap
Max. The only thing that we noticed was that TCP connections
went down right after the restart. I did open up Jconsole under
Java and I did force a garbage collection but that didn't seem to
help.
We do have an Oracle Grid Control and we did get an alert in
regards to Metric: [HTTP Transaction] Perceived Time per Page
going past thresholds but not sure if that was just an old alert
with and old range that was set up a long time ago or is a really
valid clue. Since this is PRD we had to get it back up and
running so all I did was increase the Tomcat Xmx Heap size and
restarted. I'm not really confident that is the solution since
as mentioned you tend to see a clear out of memory error if it
was too small.
1) Does this sound like a known issue with this earlier
version of Tomcat?

No.

Post by Louis Zipes
2) Should I turn up any logging on Tomcat and if so which
ones?

Not yet.

Post by Louis Zipes
3) We didn't do a JSTACK dump while it was happening. Would that have been useful?

Absolutely.

Post by Louis Zipes
4) Do we need to play around with MaxThreads and/or
MaxConnections. We do have maxThreads in our server.mxl but in
DEV when we turned it down to a value = 5 hoping to overwhelm
it nothing bad happened.

Don't change anything, yet.

Post by Louis Zipes
Once again, we are limited to what we could do and collect since
it was PRD and we needed to restart it. We restarted the Tomcat
service and everything is processing fine for right now. I will
note that that we did have that bad Windows patch that prevented
it from stopping and starting cleanly
(https://stackoverflow.com/questions/51498291/tomcat-lockup-on-shutdo

w
n)

Post by Louis Zipes

Post by Louis Zipes
but we have taken the break fix patch and the daily restarts
seem to be fine since then.
Any comments/suggestions are appreciated!

Your most likely problem is database connection pool
mismanagement: connections aren't properly released and the pool
empties. All threads are left waiting on available database
connections which will never be replenished.
-chris
---------------------------------------------------------------------
This message is for intended addressee(s) only and may contain
information that is confidential, proprietary or exempt from
disclosure. If you are not the intended recipient, please contact
the sender immediately. Unauthorized use or distribution is
prohibited and may be unlawful.
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Louis Zipes

2018-09-27 12:49:54 UTC

Permalink

Chris,
I looked through the log some more and I see all of the types of Thread Statuses. Blocked, Runnable, Waiting, etc.. Any in particular that I should concentrate on?

Ex.
"http-bio-7005-exec-128" daemon prio=6 tid=0x0000000026466800 nid=0x40e4 waiting for monitor entry [0x00000000432ae000]
java.lang.Thread.State: BLOCKED (on object monitor)
at com.demantra.applicationServer.servlets.notifications.UserNotificationHelper.execute(UserNotificationHelper.java:117)
- waiting to lock <0x000000054d652c08> (a com.demantra.applicationServer.metaDataObjects.user.UserList)

ODBC on the actual Window machine hosting Tomcat is Oracle in OraClient11g_home1 (we have a 12c Oracle database) with a pool timeout set to 60. Should I be looking to turn on some tracing on the driver?

Thanks, Louis

-----Original Message-----
From: Christopher Schultz [mailto:***@christopherschultz.net]
Sent: Wednesday, September 26, 2018 7:30 PM
To: ***@tomcat.apache.org
Subject: Re: Application hanging on Tomcat 7.0.54

- - - external message, proceed with caution - - -

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Louis,

at java.util.concurrent.locks.LockSupport.parkNanos(Unknown Source)

Post by Louis Zipes
at
java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.

awaitNanos(Unknown

This thread is waiting for a task, and is essentially idle. You will
have many of these on a non-busy system.

What are the other threads doing?

Post by Louis Zipes
Locked ownable synchronizers: - None

Post by Louis Zipes
Any comments/suggestions are appreciated!

Your most likely problem is database connection pool
mismanagement: connections aren't properly released and the pool
empties. All threads are left waiting on available database
connections which will never be replenished.
I'm using the ojdbc6.jar if that is what you are referring to or is
there a better setting somewhere.

ODBC? What is your database?

- -chris

Post by Louis Zipes
-----Original Message----- From: Christopher Schultz
Application hanging on Tomcat 7.0.54
- - - external message, proceed with caution - - -
Louis,

Post by Louis Zipes
Hi all, Tomcat 7.0.54 running on Windows 2012
We are running a third party application on Tomcat and today we
have intermittently run in issues where the application stops
working. The big changes in our system is that we have added
more end users and we are at year end so of course everyone is
hitting the system hard. Even if we force a log out of all users
and stop all background jobs then the application doesn't
recover.
We see no active sessions on the database (our application is
connecting to an Oracle database) and I see no clear error
messages in either our third party application logs or the Tomcat
logs (ex. OutofMemory). When we go to the Windows Task Manager
we did not see the machine's Memory max'd out but admittedly I
didn't look at the Java session to see if was reaching its Heap
Max. The only thing that we noticed was that TCP connections
went down right after the restart. I did open up Jconsole under
Java and I did force a garbage collection but that didn't seem to
help.
We do have an Oracle Grid Control and we did get an alert in
regards to Metric: [HTTP Transaction] Perceived Time per Page
going past thresholds but not sure if that was just an old alert
with and old range that was set up a long time ago or is a really
valid clue. Since this is PRD we had to get it back up and
running so all I did was increase the Tomcat Xmx Heap size and
restarted. I'm not really confident that is the solution since
as mentioned you tend to see a clear out of memory error if it
was too small.
1) Does this sound like a known issue with this earlier
version of Tomcat?

No.

Post by Louis Zipes
2) Should I turn up any logging on Tomcat and if so which
ones?

Not yet.

Post by Louis Zipes
3) We didn't do a JSTACK dump while it was happening. Would that have been useful?

Absolutely.

Post by Louis Zipes
4) Do we need to play around with MaxThreads and/or
MaxConnections. We do have maxThreads in our server.mxl but in
DEV when we turned it down to a value = 5 hoping to overwhelm
it nothing bad happened.

Don't change anything, yet.

Post by Louis Zipes
Once again, we are limited to what we could do and collect since
it was PRD and we needed to restart it. We restarted the Tomcat
service and everything is processing fine for right now. I will
note that that we did have that bad Windows patch that prevented
it from stopping and starting cleanly
(https://stackoverflow.com/questions/51498291/tomcat-lockup-on-shutdo

w
n)

Post by Louis Zipes

Post by Louis Zipes
but we have taken the break fix patch and the daily restarts
seem to be fine since then.
Any comments/suggestions are appreciated!

Your most likely problem is database connection pool
mismanagement: connections aren't properly released and the pool
empties. All threads are left waiting on available database
connections which will never be replenished.
-chris
---------------------------------------------------------------------
This message is for intended addressee(s) only and may contain
information that is confidential, proprietary or exempt from
disclosure. If you are not the intended recipient, please contact
the sender immediately. Unauthorized use or distribution is
prohibited and may be unlawful.
---------------------------------------------------------------------

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Т��ХF�V�7V'67&�&R�R��âW6W'2�V�7V'67&�&TF��6B�6�R��&pФf�"FF�F��6��G2�R�

Suvendu Sekhar Mondal

2018-09-27 13:49:26 UTC

Permalink

Post by Louis Zipes
Chris,
I looked through the log some more and I see all of the types of Thread
Statuses. Blocked, Runnable, Waiting, etc.. Any in particular that I
should concentrate on?

Louis, can you please take multiple thread dumps(at least 3) with 5sec
interval? You need to look for threads which are not moving at all or
moving very slowly. They could be in any state. In worst case scenario you
might see some blocking or deadlock. That will give you lead on what's
going on inside the container. You can use IBM's thread dump analyzer for
that.

Ex.

Post by Louis Zipes
"http-bio-7005-exec-128" daemon prio=6 tid=0x0000000026466800 nid=0x40e4
waiting for monitor entry [0x00000000432ae000]
java.lang.Thread.State: BLOCKED (on object monitor)
at
com.demantra.applicationServer.servlets.notifications.UserNotificationHelper.execute(UserNotificationHelper.java:117)
- waiting to lock <0x000000054d652c08> (a
com.demantra.applicationServer.metaDataObjects.user.UserList)
ODBC on the actual Window machine hosting Tomcat is Oracle in
OraClient11g_home1 (we have a 12c Oracle database) with a pool timeout set
to 60. Should I be looking to turn on some tracing on the driver?
Thanks, Louis
-----Original Message-----
Sent: Wednesday, September 26, 2018 7:30 PM
Subject: Re: Application hanging on Tomcat 7.0.54
- - - external message, proceed with caution - - -
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
Louis,

at java.util.concurrent.locks.LockSupport.parkNanos(Unknown Source)

Post by Louis Zipes
at
java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.

awaitNanos(Unknown

This thread is waiting for a task, and is essentially idle. You will
have many of these on a non-busy system.
What are the other threads doing?

Post by Louis Zipes
Locked ownable synchronizers: - None

Post by Louis Zipes
Any comments/suggestions are appreciated!

Your most likely problem is database connection pool
mismanagement: connections aren't properly released and the pool
empties. All threads are left waiting on available database
connections which will never be replenished.
I'm using the ojdbc6.jar if that is what you are referring to or is
there a better setting somewhere.

ODBC? What is your database?
- -chris

Post by Louis Zipes
-----Original Message----- From: Christopher Schultz
Application hanging on Tomcat 7.0.54
- - - external message, proceed with caution - - -
Louis,

Post by Louis Zipes
Hi all, Tomcat 7.0.54 running on Windows 2012
We are running a third party application on Tomcat and today we
have intermittently run in issues where the application stops
working. The big changes in our system is that we have added
more end users and we are at year end so of course everyone is
hitting the system hard. Even if we force a log out of all users
and stop all background jobs then the application doesn't
recover.
We see no active sessions on the database (our application is
connecting to an Oracle database) and I see no clear error
messages in either our third party application logs or the Tomcat
logs (ex. OutofMemory). When we go to the Windows Task Manager
we did not see the machine's Memory max'd out but admittedly I
didn't look at the Java session to see if was reaching its Heap
Max. The only thing that we noticed was that TCP connections
went down right after the restart. I did open up Jconsole under
Java and I did force a garbage collection but that didn't seem to
help.
We do have an Oracle Grid Control and we did get an alert in
regards to Metric: [HTTP Transaction] Perceived Time per Page
going past thresholds but not sure if that was just an old alert
with and old range that was set up a long time ago or is a really
valid clue. Since this is PRD we had to get it back up and
running so all I did was increase the Tomcat Xmx Heap size and
restarted. I'm not really confident that is the solution since
as mentioned you tend to see a clear out of memory error if it
was too small.
1) Does this sound like a known issue with this earlier
version of Tomcat?

No.

Post by Louis Zipes
2) Should I turn up any logging on Tomcat and if so which ones?

Not yet.

Post by Louis Zipes
3) We didn't do a JSTACK dump while it was happening. Would
that have been useful?

Absolutely.

Post by Louis Zipes
4) Do we need to play around with MaxThreads and/or
MaxConnections. We do have maxThreads in our server.mxl but in
DEV when we turned it down to a value = 5 hoping to overwhelm
it nothing bad happened.

Don't change anything, yet.

Post by Louis Zipes
Once again, we are limited to what we could do and collect since
it was PRD and we needed to restart it. We restarted the Tomcat
service and everything is processing fine for right now. I will
note that that we did have that bad Windows patch that prevented
it from stopping and starting cleanly
(https://stackoverflow.com/questions/51498291/tomcat-lockup-on-shutdo

w
n)

Post by Louis Zipes

Post by Louis Zipes
but we have taken the break fix patch and the daily restarts
seem to be fine since then.
Any comments/suggestions are appreciated!

Your most likely problem is database connection pool
mismanagement: connections aren't properly released and the pool
empties. All threads are left waiting on available database
connections which will never be replenished.
-chris
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Christopher Schultz

2018-09-28 22:39:56 UTC

Permalink

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Louis,

Post by Louis Zipes
I looked through the log some more and I see all of the types of
Thread Statuses. Blocked, Runnable, Waiting, etc.. Any in
particular that I should concentrate on?

The thread state doesn't always tell the whole story. Sometimes, it's
shown as RUNNABLE but it really means it's blocked. The stack trace is
more useful.

Post by Louis Zipes
Ex. "http-bio-7005-exec-128" daemon prio=6 tid=0x0000000026466800
nid=0x40e4 waiting for monitor entry [0x00000000432ae000]
java.lang.Thread.State: BLOCKED (on object monitor) at
com.demantra.applicationServer.servlets.notifications.UserNotification

Helper.execute(UserNotificationHelper.java:117)
- - waiting to lock <0x000000054d652c08> (a
com.demantra.applicationServer.metaDataObjects.user.UserList)

That certainly looks like it's waiting on something. If, as Suvendu
suggests, you take more than one thread-dump in a row -- maybe 10
seconds between dumps -- and compare them, you can detect whether or
not those threads just happen to be waiting one time, or if they are
waiting forever.

Post by Louis Zipes
ODBC on the actual Window machine hosting Tomcat is Oracle in
OraClient11g_home1 (we have a 12c Oracle database) with a pool
timeout set to 60. Should I be looking to turn on some tracing on
the driver?

60 what?

Enabling tracing is likely to generate a LOT of logging output. You
can probably discover a lot from thread dumps without changing anything.

- -chris
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Guang Chao

2018-09-27 03:45:05 UTC

Permalink

Post by Louis Zipes
Problem just re-occurred and so I was able to at least get a JSTACK (I
assume it was Tomcat since it was the Java using the most memory on the
machine). Here is the reoccurring message. I get more hits on but haven't
dug through all of the Google hits yet (due to multi-tasking) so apologies
up front if there is a simple answer to this.
"Event_Manager_1413" daemon prio=6 tid=0x0000000024856000 nid=0x40c4
waiting on condition [0x0000000042dae000]
java.lang.Thread.State: TIMED_WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000005ab45f7b8> (a
java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.parkNanos(Unknown Source)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(Unknown
Source)
at java.util.concurrent.LinkedBlockingQueue.poll(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.getTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

Do you lock from memory or database? Make sure locking sequence is
consistent all across the application. Meaning if you have

Lock A
Lock B
Lock C

You dont want another logic that locks something in another order. E.g.

Lock B
Lock A
Lock C

Because that will cause deadlocks.

Post by Louis Zipes
- None

Post by Louis Zipes
Any comments/suggestions are appreciated!

connections aren't properly released and the pool empties. All threads
are left waiting on available database connections which will never be
replenished.
I'm using the ojdbc6.jar if that is what you are referring to or is there
a better setting somewhere.

What db connection pool are you using? Are you letting tomcat manage it via
Context.xml and get connection via JNDI? Or are you managing inside the
application?

Post by Louis Zipes
-----Original Message-----
Sent: Wednesday, September 26, 2018 3:46 PM
Subject: Re: Application hanging on Tomcat 7.0.54
- - - external message, proceed with caution - - -
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
Louis,

No.

Post by Louis Zipes
2) Should I turn up any logging on Tomcat and if so which ones?

Not yet.

Post by Louis Zipes
3) We didn't do a JSTACK dump while it was happening. Would that have been useful?

Absolutely.

Don't change anything, yet.

Post by Louis Zipes
but we have taken the break fix patch and the daily restarts seem
to be fine since then.
Any comments/suggestions are appreciated!

connections aren't properly released and the pool empties. All threads
are left waiting on available database connections which will never be
replenished.
- -chris
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Jäkel, Guido

2018-09-27 06:29:03 UTC

Permalink

Dear Louis,

I would recommend to use a tool like JVisualVM (with Plugins*) to take a look on this things while it's still running or have blocked. You may live watch things like running threads or the Java heap occupation or investigate JVM, Java and Tomcat parameters (and even run some actions) via JMX with "MBean-Explorer". You may trigger to generate a heap dump or force FullGC and even do CPU or Memory profiling.

The Tomcat JDBC Connection Pool for instance provide a MBean view for every connection with it's parameters. You may live watch the number of active, idle, ... connections (with a "well hidden" chart feature: Double-Click to expand some value representations; this here to a chart)

Tomcat (i.e. Catalina) have something like a running request scoreboard, also. You may take and identify from that all long running or blocked requests. On the MBean, it's at "Catalina|RequestProcessor|<connector>|<connector-pool-member>|currentURI" and corresponding parameters.

(*) You would have to install some plugins inside the JVisualVM Tool, e.g. "Visual GC", "VisualVM Buffer Monitor", "Thread Inspector", "VisualVM BMeans"

Greetings

Guido

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Louis Zipes

2018-09-27 13:19:25 UTC

Permalink

Hi Guido,
Even though these hangs are critical to find, any plugin or additional code that I wish to put on our PRD server have to go through our SOX process so it can be cumbersome. Are any of the monitoring techniques that you mention 'out of the box' with Tomcat 7.0.54 or JDK 1.7. I can certainly open the JCONSOLE in the java bin folder but I don't have those nice Spring Boot Add-ons documented in say https://stackoverflow.com/questions/36587023/how-to-debug-log-tomcat-jdbc-connection-pools-connections

Post by JÃ¤kel, Guido
The Tomcat JDBC Connection Pool for instance provide a MBean view for every connection with it's parameters. You may live watch the number of active, idle, ... connections (with a "well hidden" chart feature: Double-Click to expand some value representations; this here to a chart)

Thank you!

-----Original Message-----
From: Jäkel, Guido [mailto:***@dnb.de]
Sent: Thursday, September 27, 2018 2:29 AM
To: 'Tomcat Users List'
Subject: RE: Application hanging on Tomcat 7.0.54

- - - external message, proceed with caution - - -

Dear Louis,

I would recommend to use a tool like JVisualVM (with Plugins*) to take a look on this things while it's still running or have blocked. You may live watch things like running threads or the Java heap occupation or investigate JVM, Java and Tomcat parameters (and even run some actions) via JMX with "MBean-Explorer". You may trigger to generate a heap dump or force FullGC and even do CPU or Memory profiling.

The Tomcat JDBC Connection Pool for instance provide a MBean view for every connection with it's parameters. You may live watch the number of active, idle, ... connections (with a "well hidden" chart feature: Double-Click to expand some value representations; this here to a chart)

Tomcat (i.e. Catalina) have something like a running request scoreboard, also. You may take and identify from that all long running or blocked requests. On the MBean, it's at "Catalina|RequestProcessor|<connector>|<connector-pool-member>|currentURI" and corresponding parameters.

(*) You would have to install some plugins inside the JVisualVM Tool, e.g. "Visual GC", "VisualVM Buffer Monitor", "Thread Inspector", "VisualVM BMeans"

Greetings

Guido

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Christopher Schultz

2018-09-28 22:42:37 UTC

Permalink

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Louis,

Post by Louis Zipes
Even though these hangs are critical to find, any plugin or
additional code that I wish to put on our PRD server have to go
through our SOX process so it can be cumbersome. Are any of the
monitoring techniques that you mention 'out of the box' with
Tomcat 7.0.54 or JDK 1.7. I can certainly open the JCONSOLE in the
java bin folder but I don't have those nice Spring Boot Add-ons
documented in say
https://stackoverflow.com/questions/36587023/how-to-debug-log-tomcat-j

dbc-connection-pools-connections

You
don't need Spring Boot or anything like that. jconsole (or, better
yet VisualVM) can certainly observe your connection pool status as well
as runtime thread state, etc.

- -chris
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Louis Zipes

2018-10-01 12:01:53 UTC

Permalink

Ok, thanks as always for the advice! We think we figured out the user error(s) that caused the issue but I'm now more comfortable with pulling the Thread Dumps/VisualVM quicker so we can at least get those before we have to restart the application.

Thanks, Louis

Post by Louis Zipes
timeout set to 60. Should I be looking to turn on some tracing on the
driver?

60 what?

60 was the Pool Timeout

-----Original Message-----
From: Christopher Schultz [mailto:***@christopherschultz.net]
Sent: Friday, September 28, 2018 6:43 PM
To: ***@tomcat.apache.org
Subject: Re: Application hanging on Tomcat 7.0.54

- - - external message, proceed with caution - - -

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Louis,