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In order to simplify testing, I asked our java developer to create a simple
method to call from rpg that made no connections at all to the iSeries. I
created an rpgle program to call the method. I have code that adds a link
to the directory, adds the .jar to the environmental variable, uses
getJniEnv and BegObjGroup (jniutil), calls the java method (defined as a
Static Extproc), ends the object group, removes the environmental variables
and removes the link. When I then check the .jar file on the ifs the usage
is 'in use' under the job that I ran the rpg program in. I am unable to
restore that object or release it in any way until that session is signed
off.
Having said all that and testing past versions, I've come to the conclusion
that this was most likely the case for years on installs, we are just seeing
it more often as the use of java has become more prevalent. If have found
nothing in my searches as a work around, unless anyone has any ideas.
Thanks
-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx [mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Dan Kimmel
Sent: Tuesday, November 02, 2010 10:36 AM
To: Java Programming on and around the IBM i
Subject: RE: .jar files in use on a restore
Are you talking about database connections or connections to run native
commands and programs?
JDBC connections use JT400.jar (JTOPEN.jar) and classes from the jre. I
doubt you're replacing any of those. What jars are failing to replace? Are
they your own code?
If you are using the non-thread-safe versions of the connection commands,
those connections occur in jni programs that run within the same job as the
jvm. The thread-safe versions are all native java and jdk code communicating
with server jobs that usually run in the QUSRWRK subsystem. That might make
a difference when trying to shut down the jvm via the activation group to
free up connections to your jar files.
Just as an afterthought, are you doing anything to your java environment
that would free up hard links before you end the activiation group?
-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx [mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Anna Abt
Sent: Tuesday, November 02, 2010 7:33 AM
To: 'Java Programming on and around the IBM i'
Subject: RE: .jar files in use on a restore
The activation group is ended at the end of the rpg processes and also ended
at the beginning of an install/upgrade. As this seems to be intermittent
and a fairly new occurrence, I'm leaning toward something the java code is
doing in creating an iSeries connection. I am running more tests on our
systems to see if I can get more details.
-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx [mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Dan Kimmel
Sent: Monday, November 01, 2010 6:06 PM
To: Java Programming on and around the IBM i
Subject: RE: .jar files in use on a restore
As long as that RPG program has pointers to the instantiated object, you're
not going to be able to replace the jars containing the code for that
object. There are other ways to do it, but you're probably going to have to
end the activation group where the RPG program is running in order to remove
the locks on the jar files. I don't think the traditional methods of
detecting locks are going to find locks on your jar files. WRKOBJLCK, for
instance, looks for objects referenced by the job and a jar file is not an
object. However, the file is "in use".
When RPG uses a java method, RPG invokes the JVM and the JVM "opens" the jar
files. The JVM doesn't need the jar file anymore after the class and object
are instantiated in memory and might close it, except for garbage
collection. The JVM must hold a lock on the jar file as long as it is
running as it might need to read the class from the jar again if garbage
collection has removed the class object when RPG needs to build a new
instance.
Depending on the operating system level, the jvm may run in a separate job.
In any case it is a unique thread or threads whether in the same job as the
RPG or in its own job. All the stuff that connects the RPG to the jvm is in
an activation group. If you have the RPG program running in some activation
group outside the default activation group, the jvm-glue probably runs in
the same activation group. If your RPG program is running in the default
activation group all that glue is probably in its own activation group. I
say probably here, because I'm reporting behavior as I see it; I don't
actually have documentation on this.
So my take on how to do the upgrade you describe would be to have the CL
that runs the RPG program end the activation group that contains the RPG
program; do the jar file replaces; then start the RPG program back up again.
This should work in just about all operating systems and versions of java.
Anyone else care to contribute?
-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx [mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Anna Abt
Sent: Monday, November 01, 2010 4:07 PM
To: 'Java Programming on and around the IBM i'
Subject: RE: .jar files in use on a restore
There was no OS upgrade or PTF applied on our systems since the problem
started, I do not know about clients. We run v5r3, v5r4, and v5r6 here and
support back to v5r2 for our customer base. RPG invokes the jvm and sets
the class path and environmental variables and begins and ends the object
group. RPG calls the methods within an instantiated object. Before any
upgrades locks on all rpg objects are checked and the upgrade will not
continue if it cannot allocate all objects. The basic processing on the rpg
side has been the same for a number of years. Some java methods were
connecting to the iSeries for data retrieval.
-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx [mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Dan Kimmel
Sent: Monday, November 01, 2010 4:28 PM
To: Java Programming on and around the IBM i
Subject: RE: .jar files in use on a restore
I think the connection pool is a red herring. The problem probably has more
to do with an OS upgrade or PTF applied in the last year. I'd need to know a
lot more to offer any other suggestions. What OS version? What kind of
programs use the jar files? How is the jvm invoked? Where does the rpg
program enter the picture? Is the rpg program calling methods on objects in
the jar files? Do you stop all instances of the rpg program before
attempting to replace the jar files?
-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx [mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Anna Abt
Sent: Monday, November 01, 2010 2:38 PM
To: java400-l@xxxxxxxxxxxx
Subject: .jar files in use on a restore
Recently we have run into an issue when trying to run upgrades of our
software. I have a clle program that does a restore to an ifs directory
with new .jar files. There have been instances lately where objects have
not been restored because they are in use. Speaking with our java
programmers I did learn that there was a change made in the past year to
create a connection pool and keep it open for a longer period of time for
performance enhancing reasons. Doing some testing, we removed the
connection and are now sending the data from the rpg programs to the java
methods. We are still finding that the .jar files stay in a "in use" state.
Can anyone tell me how we might get around this or why this seems to be
happening all of a sudden? We even did a simple test adding a classpath of
3 .jar files and running 2 programs, the first opens a connection and prints
and the second closes the connection. Those 3 files still are in use and
unable to run a restore against.
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