Name: diC59631 Date: 11/11/98


1. Attached is the source code of a class test.java
2. I have tried with JDK 1.1.5 and 1.2 beta 2

To test ->
  1. Create dir say 'maxFiles'
  2. Copy test.class in this dir
  3. create 'test' directory in 'maxFiles'
  4. run java test 3000 1 10 testWith the above command line the 'test' will create 10 thread and each thread will attempt to open 3000 files
for single thread use:
java test 3000 1 1 test
 I have even tried with ( -ms33554432 -mx67108867 ) flags for runtime, it does not make any difference.

 In short, it does not matter how many thread are opened or what is Java heap size, I am not able
to open in total more than 2035 files.

// -------------------------------- Sorce Code of test.java -------------
import java.io.*;
import java.util.*;



/**
Class to test max. number of open files.

Author: Bharat Gogia

E-mail: ###@###.###

Dt:23 Feb. 1998

**/



class test extends Thread
{

   static Vector m_BrnIdxArray = null;

int startVal;
int maxVal;
String path;
int thID;


static void zleep(long ms)
{
try
{
Thread.currentThread().yield();
Thread.currentThread().sleep(ms);
}
catch (InterruptedException ie)
{
}
}

public test(int stVal, int mxVal, String sPath, int tID)
{
maxVal = mxVal;
startVal = stVal;
path = sPath;
}

static public void main(String [] args)
{
int maxVal = Integer.parseInt(args[0]);
int startVal = Integer.parseInt(args[1]);
int totThread = Integer.parseInt(args[2]);
String path = new String (args[3]);

for (int i =0; i< totThread ; i++ )
{
test t1 = new test( (startVal + (i*maxVal)), maxVal, path, i);
t1.start();
zleep(10);
}

}

public void run()
{
byte buf[] = new byte[512];
m_BrnIdxArray = new Vector();
   RandomAccessFile m_brnDatFile = null;
System.out.println("Starting " + System.currentTimeMillis() + "\r\n" );
for (int i=startVal; i < (startVal+maxVal) ; i++ )
{
String fname ;
fname = (path + FormatIntToString(i, "0000000000",'d') + ".tst");
try
{
m_brnDatFile = new RandomAccessFile(fname, "rw");
m_brnDatFile.write(buf);
m_BrnIdxArray.addElement(m_brnDatFile);
zleep(20);
}
catch (Exception eio)
{
System.out.println("\r\n" + eio.getMessage() + " " + eio);
System.out.println("Aborting " + System.currentTimeMillis() + "\r\n" );
m_brnDatFile = null;
m_BrnIdxArray.removeAllElements();
System.exit(0);
}
System.out.print("Opened " + fname + " Thread: " + thID + "\r" );
fname = null;
}
System.out.println("Closing " + System.currentTimeMillis() + "\r\n" );
}


    public static String FormatIntToString(int i, String frmt, char type)
       {
        String target;
        StringBuffer strbuf = new StringBuffer(frmt);
String strInt;


        try
           {
           if(type == 'x' || type == 'X')
strInt = Integer.toHexString(i);
else
strInt = Integer.toString(i);

if (strInt.length() > frmt.length())
{
strInt = strInt.substring(0, frmt.length());
}

strbuf.insert( (frmt.length() - strInt.length()), strInt);

           strbuf.setLength(frmt.length());
           target = new String(strbuf);

           }
        catch (StringIndexOutOfBoundsException sie)
            {
System.out.println("Exception in FormatIntToString " + sie.getMessage());
            target = null;
}
            
       return(target);
       }



}
//----------------------------------- End of Soruce Code ----------

 To clarify the issue, on win32 system there are three
ways to open a file:
1: Using Win32 API
2: Using MFC class framework lib.
3: using C-Library API (open() and fopen())

Other than the third option, i.e. option 1 and 2 have practically no
limitation in opening number of files. The third method is restricted
(for the reason not known to me) to open only approx. 2035 files. That
is why MS JVM is able to open unlimited (practically) files, but SUN JVM
fails after 2035 files (my guess is it is using 3rd method to open
file).

 The case is true only only on Win32 OS. The reason this is serious
problem ans we have to revert to MS JVM is because we werr writing high
scalable server in Java. I am sure you understand that Java as an API
must compatible on all platform, some of which are Solaris, NT(Win32),
Novell etc...

Hope this helps you to update your JVM.
(Review ID: 25523)
======================================================================

Name: nt126004 Date: 06/05/2002


FULL PRODUCT VERSION :
C:\>java -version
java version "1.4.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-b92)
Java HotSpot(TM) Client VM (build 1.4.0-b92, mixed mode)


FULL OPERATING SYSTEM VERSION :
Windows 2000 SERVER

ADDITIONAL OPERATING SYSTEMS :

Windows 2000 Professional


A DESCRIPTION OF THE PROBLEM :
File creation is seriously broken in the JDK 1.4 for
Windows.

Unlike most unix systems, Windows 2000 has *NO*
file descriptor or open file limitations. A simple
5 line C program can create as many new files
as desired (I created about 50,000 as a test).

I repeat this: there are *NO* operating system
limitations to creating files [on Windows 2000].

However, with JDK 1.4, there is a "too many open files"
exception after creating about 2033 files. This is
true, regardless of whether I am running on Windows
2000 Server or Professional. (By the way, I am doing
everything as "Administrator").

This is clearly a serious JVM bug that needs to be
corrected ASAP. Serious server side applications cannot
run if artificially constrained by this JVM limitation.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. see attached program.
2. java maxfiles 10000
3. see attached stack trace

EXPECTED VERSUS ACTUAL BEHAVIOR :
Expected: Successful completion

Actual: "too many open files" exception.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
C:\javatesting\javatesting\misc\filetest>java maxfiles 10000
Exception in thread "main" java.io.FileNotFoundException: file2033 (Too many
open files)
        at java.io.FileOutputStream.open(Native Method)
        at java.io.FileOutputStream.<init>(FileOutputStream.java:176)
        at java.io.FileOutputStream.<init>(FileOutputStream.java:131)
        at maxfiles.main(maxfiles.java:14)

This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.io.*;
import java.util.*;

/**
Is there a JVM limitation to create files on Windows 2000 Server ?

Usage:
java maxfiles <number-of-files>

Note:
Creates files in the same directory where "java" was invoked.
Create a test directory for this purpose !
**/
public class maxfiles
{
static int count = 0;
static List files = new ArrayList();

public static void main(String args[]) throws Exception
{
    for (int n = 0; n < Integer.parseInt(args[0]); n++) {
File f = new File("file" + count++);
//save ref, so not gc'ed
files.add(new PrintStream(new FileOutputStream(f)));
}
    Iterator it = files.iterator();
    while (it.hasNext()) {
PrintStream out = ( PrintStream) it.next();
out.println("foo");
out.flush();
}
System.out.println("current files open: " + files.size());
} //~main

} //~class maxfiles
---------- END SOURCE ----------
(Review ID: 148202)
======================================================================