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Posted to derby-user@db.apache.org by Jason Boehle <jb...@gmail.com> on 2006/09/19 19:34:55 UTC
question about shutdown
I am using Derby embedded in an application. If the database is
shutdown via opening a connection to
jdbc:derby:/path/to/db;shutdown=true, what should happen to existing
open connections to that database?
Re: question about shutdown
Posted by Jason Boehle <jb...@gmail.com>.
On 9/19/06, Stanley Bradbury <St...@gmail.com> wrote:
> Jason Boehle wrote:
> > On 9/19/06, Stanley Bradbury <St...@gmail.com> wrote:
> >> Jason Boehle wrote:
> >> > I am using Derby embedded in an application. If the database is
> >> > shutdown via opening a connection to
> >> > jdbc:derby:/path/to/db;shutdown=true, what should happen to existing
> >> > open connections to that database?
> >> >
> >> Any existing connections to that DB will be closed. Any attempts to use
> >> such a connection will result in an exception.
> >
> > I wrote a small test that exercised this, and Derby leaks memory like
> > crazy (almost 1MB per database) if this happens. Here is the code for
> > my test:
> >
> > public class TestDerbyBug {
> > public static void main(String[] args) {
> > try {
> >
> > Class.forName("org.apache.derby.jdbc.EmbeddedDriver").newInstance();
> > while (true) {
> > final String dir =
> > System.getProperty("java.io.tmpdir") + java.io.File.separator +
> > "TestDerbyBug-" + Math.abs(new java.util.Random().nextInt());
> > final String url = "jdbc:derby:" + dir;
> > java.sql.Connection conn =
> > java.sql.DriverManager.getConnection(url + ";create=true");
> > // oops, forgot to close conn before shutting down...
> > try {
> > java.sql.DriverManager.getConnection(url +
> > ";shutdown=true");
> > assert false; // shouldn't get here
> > }
> > catch (java.sql.SQLException e) {
> > // ignore, shutdown is supposed to throw
> > }
> > // finally got around to remembering to close conn
> > conn.close();
> > }
> > }
> > catch (Throwable t) {
> > t.printStackTrace();
> > }
> > }
> > }
> >
> > If you run that class with a max heap of 16MB (-Xmx16m), it will only
> > be able to create about 18-20 databases before running out of memory.
> > If you move the 'conn.close()' line above the inner try statement, no
> > memory is leaked and it can run for at least 15 minutes (I got bored
> > and killed it at that point). I tried this with 10.1.2.1, 10.1.3.1,
> > and 10.2.1.3-beta and got the same results on all releases. I am
> > running it under JRE 1.5.0_08.
> >
> > There is a similar bug reported, DERBY-23, that is reported fixed in
> > 10.2, if that helps at all.
> >
> > Obviously, the easiest fix is to make sure to clean up my connections
> > before shutting down. :)
> >
> Hi Jason -
> From what I see Derby is acting as expected. What you are observing is
> Derby's memory allocation process. Derby will continue to allocate
> memory until it reaches the set by it's various configuration properties
> (most notably: pageCacheSize). At this point Derby's memory footprint
> will become stable. For most schemas the default settings for Derby
> allow it to function well with the default JVM size of 64 Mb. As you
> found out in your test, should you reduce the amount of memory allocated
> to the JVM you will eventually get OutOfMemoryExceptions. If you need
> Derby to run with a smaller footprint and do not need the better
> performance of a larger pageCache, reduce the Derby pageCacheSize - the
> minimum setting is 40.
Stanley,
I thought the default pageCacheSize is 1000, the default pageSize is
4096, which would make the default page cache max be 4MB. Is that per
database or per Derby instance?
If I change the code to close the open connection before shutting
down, Derby can run all day...so it doesn't seem to me like Derby is
closing open connections when shutting down.
I will try it with a smaller pageCacheSize, but I think that will just
let the code run longer, still resulting in an out of memory error.
-Jason
Re: question about shutdown
Posted by Stanley Bradbury <St...@gmail.com>.
Jason Boehle wrote:
> On 9/19/06, Stanley Bradbury <St...@gmail.com> wrote:
>> Jason Boehle wrote:
>> > I am using Derby embedded in an application. If the database is
>> > shutdown via opening a connection to
>> > jdbc:derby:/path/to/db;shutdown=true, what should happen to existing
>> > open connections to that database?
>> >
>> Any existing connections to that DB will be closed. Any attempts to use
>> such a connection will result in an exception.
>
> I wrote a small test that exercised this, and Derby leaks memory like
> crazy (almost 1MB per database) if this happens. Here is the code for
> my test:
>
> public class TestDerbyBug {
> public static void main(String[] args) {
> try {
>
> Class.forName("org.apache.derby.jdbc.EmbeddedDriver").newInstance();
> while (true) {
> final String dir =
> System.getProperty("java.io.tmpdir") + java.io.File.separator +
> "TestDerbyBug-" + Math.abs(new java.util.Random().nextInt());
> final String url = "jdbc:derby:" + dir;
> java.sql.Connection conn =
> java.sql.DriverManager.getConnection(url + ";create=true");
> // oops, forgot to close conn before shutting down...
> try {
> java.sql.DriverManager.getConnection(url +
> ";shutdown=true");
> assert false; // shouldn't get here
> }
> catch (java.sql.SQLException e) {
> // ignore, shutdown is supposed to throw
> }
> // finally got around to remembering to close conn
> conn.close();
> }
> }
> catch (Throwable t) {
> t.printStackTrace();
> }
> }
> }
>
> If you run that class with a max heap of 16MB (-Xmx16m), it will only
> be able to create about 18-20 databases before running out of memory.
> If you move the 'conn.close()' line above the inner try statement, no
> memory is leaked and it can run for at least 15 minutes (I got bored
> and killed it at that point). I tried this with 10.1.2.1, 10.1.3.1,
> and 10.2.1.3-beta and got the same results on all releases. I am
> running it under JRE 1.5.0_08.
>
> There is a similar bug reported, DERBY-23, that is reported fixed in
> 10.2, if that helps at all.
>
> Obviously, the easiest fix is to make sure to clean up my connections
> before shutting down. :)
>
Hi Jason -
From what I see Derby is acting as expected. What you are observing is
Derby's memory allocation process. Derby will continue to allocate
memory until it reaches the set by it's various configuration properties
(most notably: pageCacheSize). At this point Derby's memory footprint
will become stable. For most schemas the default settings for Derby
allow it to function well with the default JVM size of 64 Mb. As you
found out in your test, should you reduce the amount of memory allocated
to the JVM you will eventually get OutOfMemoryExceptions. If you need
Derby to run with a smaller footprint and do not need the better
performance of a larger pageCache, reduce the Derby pageCacheSize - the
minimum setting is 40.
Re: question about shutdown
Posted by Jason Boehle <jb...@gmail.com>.
On 9/19/06, Stanley Bradbury <St...@gmail.com> wrote:
> Jason Boehle wrote:
> > I am using Derby embedded in an application. If the database is
> > shutdown via opening a connection to
> > jdbc:derby:/path/to/db;shutdown=true, what should happen to existing
> > open connections to that database?
> >
> Any existing connections to that DB will be closed. Any attempts to use
> such a connection will result in an exception.
I wrote a small test that exercised this, and Derby leaks memory like
crazy (almost 1MB per database) if this happens. Here is the code for
my test:
public class TestDerbyBug {
public static void main(String[] args) {
try {
Class.forName("org.apache.derby.jdbc.EmbeddedDriver").newInstance();
while (true) {
final String dir =
System.getProperty("java.io.tmpdir") + java.io.File.separator +
"TestDerbyBug-" + Math.abs(new java.util.Random().nextInt());
final String url = "jdbc:derby:" + dir;
java.sql.Connection conn =
java.sql.DriverManager.getConnection(url + ";create=true");
// oops, forgot to close conn before shutting down...
try {
java.sql.DriverManager.getConnection(url +
";shutdown=true");
assert false; // shouldn't get here
}
catch (java.sql.SQLException e) {
// ignore, shutdown is supposed to throw
}
// finally got around to remembering to close conn
conn.close();
}
}
catch (Throwable t) {
t.printStackTrace();
}
}
}
If you run that class with a max heap of 16MB (-Xmx16m), it will only
be able to create about 18-20 databases before running out of memory.
If you move the 'conn.close()' line above the inner try statement, no
memory is leaked and it can run for at least 15 minutes (I got bored
and killed it at that point). I tried this with 10.1.2.1, 10.1.3.1,
and 10.2.1.3-beta and got the same results on all releases. I am
running it under JRE 1.5.0_08.
There is a similar bug reported, DERBY-23, that is reported fixed in
10.2, if that helps at all.
Obviously, the easiest fix is to make sure to clean up my connections
before shutting down. :)
Re: question about shutdown
Posted by Stanley Bradbury <St...@gmail.com>.
Jason Boehle wrote:
> I am using Derby embedded in an application. If the database is
> shutdown via opening a connection to
> jdbc:derby:/path/to/db;shutdown=true, what should happen to existing
> open connections to that database?
>
Any existing connections to that DB will be closed. Any attempts to use
such a connection will result in an exception.