simple java program connecting to database server using JDBC has execution time varying all over the place

Question

I've got a very simple java program (J.java, see below) on my application server that successfully connects to an Oracle 11.2 database on a database server (both servers are Linux CentOS) using JDBC thin driver from Oracle.

As you can see from the setURL command in the Java code below, I've configured the application and database servers to sit next to each other, and they're on the same network (cross-cable connected to each other), so there's no network traffic on these (development) boxes except my code.

The problem is the execution time varies a lot. If I run it 5 times, it (seemingly randomly) could take 0.01 seconds, or 10 seconds, or 50 seconds, or over a minute to execute. If it takes over a minute (roughly), the program doesn't complete, but the error shown below is returned instead.

Any ideas what could be going on here?

--------error returned when execution take more than about 1 minute-------
gn@host7 [~/fd]# java -cp ./ojdbc6_g.jar:. J
Exception in thread "main" java.sql.SQLRecoverableException: IO Error: Connection reset
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:494)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:547)
at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:225)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:29)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:556)
at oracle.jdbc.pool.OracleDataSource.getPhysicalConnection(OracleDataSource.java:454)
at oracle.jdbc.pool.OracleDataSource.getConnection(OracleDataSource.java:328)
at oracle.jdbc.pool.OracleDataSource.getConnection(OracleDataSource.java:233)
at J.main(J.java: line 16)
Caused by: java.net.SocketException: Connection reset
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:96)
at java.net.SocketOutputStream.write(SocketOutputStream.java:136)
at oracle.net.ns.DataPacket.send(DataPacket.java:219)
at oracle.net.ns.NetOutputStream.flush(NetOutputStream.java:208)
at oracle.net.ns.NetInputStream.getNextPacket(NetInputStream.java:224)
at oracle.net.ns.NetInputStream.read(NetInputStream.java:172)
at oracle.net.ns.NetInputStream.read(NetInputStream.java:97)
at oracle.net.ns.NetInputStream.read(NetInputStream.java:82)
at oracle.jdbc.driver.T4CSocketInputStreamWrapper.readNextPacket(T4CSocketInputStreamWrapper.java:120)
at oracle.jdbc.driver.T4CSocketInputStreamWrapper.read(T4CSocketInputStreamWrapper.java:76)
at oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1158)
at oracle.jdbc.driver.T4CMAREngine.unmarshalSB1(T4CMAREngine.java:1134)
at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:307)
at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:199)
at oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:365)
at oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:812)
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:411)
... 8 more

The java code for: J.java is:

import java.sql.*;
import oracle.jdbc.*;
import oracle.jdbc.pool.OracleDataSource;

class J {

    public static void main(String args[]) throws SQLException {
    Connection conn;
    // connect to database
    OracleDataSource ds = new OracleDataSource();
    ds.setURL("jdbc:oracle:thin:hr/[email protected]:1973:mySID");
    conn = ds.getConnection();

    // create Oracle DatabaseMetaData object
    DatabaseMetaData meta = conn.getMetaData();
    // show database version
    System.out.println("Database version is " + meta.getDriverVersion());

    if ( conn != null ) {
      try { conn.close(); } catch ( Exception ex ) {}
      conn = null;
    }
    } 
}

UPDATE 1:

This looks like the potential culpret:

http://www.usn-it.de/index.php/2009/02/20/oracle-11g-jdbc-driver-hangs-blocked-by-devrandom-entropy-pool-empty/

Anyone know how to actually implement the solution provided there (see item 3 at end -- where would I find this -Djava.security.egd=file:///dev/urandom to change it?)

Answer 1

Answer is as follows (from CentOS forums):

Try editing /etc/sysconfig/rngd to contain:

# Add extra options here
EXTRAOPTIONS="-r /dev/urandom"

Then "service rngd start". If that works, then "chkconfig rngd on" will start it at boot.

See also:

http://www.linuxfromscratch.org/hints/downloads/files/entropy.txt

http://www.usn-it.de/index.php/2009/02/20/oracle-11g-jdbc-driver-hangs-blocked-by-devrandom-entropy-pool-empty/

https://www.centos.org/modules/newbb/viewtopic.php?topic_id=36209&start=0#forumpost156856

https://forums.oracle.com/forums/thread.jspa?messageID=3793101