Connections hang during long running test (no replies)

Hi,
It seems to be that during long running scaling test all
db connections hangs.

Example of hanging thread:
"pool-8-thread-10" nid=220 state=RUNNABLE
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(Unknown Source)
at
com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:114)
at
com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:161)
at
com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:189)
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2500)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2953)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2942)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3485)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1960)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2114)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2696)
- locked java.lang.Object@@7a3e
at
com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2105)
at
com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2264)
- locked java.lang.Object@@7a3e
at
org.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:96)
at
org.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:96)


The thread is in the RUNNABLE state, but socketRead0 method takes a lot of
time.

Another strange thing is that "show processlist" command shows, that MySQL
server does nothing, all process are <null> and they are in the sleep
state.

I also observed that every 30 seconds there is a lot of active query on the
MySQL server.

MySQL - 5.0.51a
Connector - 5.1.12
DBCP - 1.4

Did anybody have the same problem?