Hello,
I am having a problem with Tomcat 5.0.19 on windows with JDK
1.4.2_03.The memory that java.exe is using keeps growing till the point
that tomcat
Runs out of memory.
Using a profiler, doesn't seem to help me much. I can see the memory
being used by certain classes go up (mainly char[] and byte[] and some
tomcat classes, please see the tables below) and even reach all the way
to the point that used java heap equals to the java heap, then GC
probably kicks but, while running Tomcat throws an OutOfMemory
exception. I have allocated -Xmx896M. I'm now forcing a GC when the
free memory drops to 15%. With every GC, the freed memory is less and
less, which to me is an indication of memory leak.
I can't figure out where all those char[] objects are coming
from or why they aren't being reclaimed by the garbage collector. I
know that something is holding memory and isn't letting it go, and I
know that the leaked memory consists of char[] and byte[] objects (see
below tables). What I can't figure out is how to determine what's doing
the leaking.
After several hours of heavy usage, the GC runs and frees less
memory than the previous run. This gives me on day of normal operation
and I have to restart Tomcat after hours to be ready for the next day,
not a really acceptable solution.
I noticed the 3 tomcat classes:
org.apache.tomcat.util.buf.MessageBytes,
org.apache.tomcat.util.buf.ByteChunk and
org.apache.tomcat.util.buf.CharChunk. The memory occupied my these seems
to never be released. Can they be the cause of the multiple byte[] and
char[]?
Some info about the application/environment:
- Tomcat 5.0.19 on windows with JDK 1.4.2_03.
- MVC type web application
- front Controller dispathing requests to business classes and
forwards to appropriate JSP, passing necessary data objects in the
request object
- heavy JDBC use and DAO/DTO components, mainly using
PreparedStatement
- Oracle stored procedures and functions acccessed thru
CallableStatement
- Oracle database
I am doing the usual for closing all jdbc database related objects like
ResultSet, PreparedStatement and connections.
Here are some thoughts that I have, that could be the reason for the
leak, these are more questions:
1. DTO objects are being passed from the data layer to the
business layer and finnaly to the JSP. After using the DTOs on the JSP,
they are not explicitly set to null in the JSP. I see that all DTO
declarations are in the "service" method of the compiled JSPs. Can this
be a problem?
2. HashMaps, HashTables and LinkedHashMaps are being passed the
same way thru the layers and end up in the JSPs. These are not set to
null either. Can this be a problem?
3. PreparedStatement and CallableStatement are always closed,
but not always set to null.
Can any of these be the cause?
Below are some metrics from my environemnt:
After a several hours of heavy usage, BEFORE GC:
Name Instance count Size
char[ ] 2,200,184 425,721
kB
byte[ ] 199,003 178,902
kB
java.lang.String 1,825,003 42,773
kB
java.lang.StringBuffer 925,351 21,687
kB
<class>[ ] 679,935 19,181
kB
org.apache.naming.resources.FileDirContext$FileResourceAttributes
122,254 8,595 kB
org.apache.tomcat.util.buf.MessageBytes 117,876 5,525
kB
org.apache.tomcat.util.buf.ByteChunk 135,061 5,275
kB
org.apache.tomcat.util.buf.CharChunk 132,558 5,178
kB
java.util.HashMap$ValueIterator 97,551 3,04
...more
AFTER GC:
This is the top of the list, sorted by size:
Name Instance count Size
byte[ ] 47,866 167,877
kB
char[ ] 69,387 151,906
kB
org.apache.tomcat.util.buf.MessageBytes 117,928 5,527
kB
org.apache.tomcat.util.buf.ByteChunk 135,120 5,278
kB
org.apache.tomcat.util.buf.CharChunk 132,616 5,180
kB
<class>[ ] 71,550 4,711
kB
int[ ] 22,195 1,408
kB
java.text.DecimalFormat 7,351 804 kB
java.lang.String 32,828 769 kB
org.apache.tomcat.util.http.MimeHeaderField 28,098 658 kB
java.util.HashMap 15,598 609 kB
java.util.GregorianCalendar 7,351 516 kB
long[ ] 4,927 498 kB
java.text.DecimalFormatSymbols 7,351 402 kB
...more
As you can see, one third of the char[] and almost all of the byte[]
remain after the GC. As for the three tomcat classes, they remain almost
unchanged.
All your input will be much appreciated!
Regards,
Rossen Petkov
[EMAIL PROTECTED]
TMaG Carlsbad
1.760.918.6228
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