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From Martin Gainty <mgai...@hotmail.com>
Subject RE: java.net.SocketException: Too many open files
Date Wed, 03 Jun 2009 16:55:41 GMT

Here is the code
    void acceptConnections() {
        if( log.isDebugEnabled() )
            log.debug("Accepting ajp connections on " + port);
        while( running ) {
        try{
                MsgContext ep=createMsgContext(packetSize);
                ep.setSource(this);
                ep.setWorkerEnv( wEnv );
                this.accept(ep);

                if( !running ) break;
                
         // Since this is a long-running connection, we don't care about the small GC
         //next line gac's
                SocketConnection ajpConn=
                    new SocketConnection(this, ep);
                tp.runIt( ajpConn );
        }catch(Exception ex) {
                if (running) log.warn("Exception executing accept" ,ex);
        }
        }
    }

where org.apache.jk.core.JkHandler.java contains the createMsgContext
  public MsgContext createMsgContext() {
        return new MsgContext(8*1024);
    }

which calls org.apache.jk.core.MsgContext
    public MsgContext(int bsize) {
        try {
            c2b = new C2BConverter("iso-8859-1");
        } catch(IOException iex) {
            log.warn("Can't happen", iex);
        }
        jkIS = new JkInputStream(this, bsize);
    }

which calls org.apache.jk.common.JkInputStream
    public JkInputStream(MsgContext context, int bsize) {
        mc = context;
        bodyMsg = new MsgAjp(bsize);
        outputMsg = new MsgAjp(bsize);
    }

//which calls org.apache.jk.common.MsgAjp
  private byte buf[];
    // The current read or write position in the buffer
    private int pos;    
    /**
     * This actually means different things depending on whether the
     * packet is read or write.  For read, it's the length of the
     * payload (excluding the header).  For write, it's the length of
     * the packet as a whole (counting the header).  Oh, well.
     */
    private int len; 
    /*** The maximum packet size*/
    private int bufsize;

    /*** Constructor that takes a buffer size*/
    public MsgAjp(int bsize) {
        if(bsize < 8*1024) {
            bsize = 8*1024;
        }
        bufsize = bsize;
        buf = new byte[bsize];    
    }
3 possiblities
1)misconfig with AJP connector

2)so you're running out of heap 
tweaking JAVA_OPT minheap and maxheap parameters would help
a 2004 post http://forums.sun.com/thread.jspa?messageID=10055131 says it best

The default stack size is 256K on UNIX and on 32-bit Windows operating systems. To set Stack
size

java -XX:NewSize=128m -XX:MaxNewSize=128m -XX:SurvivorRatio=8  -Xms512m -Xmx512m

1. Setting the New generation heap size
 -XX:NewSize
 Use
this option to set the New generation Java heap size. Set this value to
a multiple of 1024 that is greater than 1MB. As a general rule, set
-XX:NewSize to be one-fourth the size of the maximum heap size.
Increase the value of this option for larger numbers of short-lived
objects.(problem is you would have to know which objects are short-lived)

Be sure to increase the New generation as you increase the number of
processors. Memory allocation can be parallel, but garbage collection
is not parallel.

2. Setting the maximum New generation heap size
 -XX:MaxNewSize
Use this option to set the maximum New generation Java heap size. Set
this value to a multiple of 1024 that is greater than 1MB.
(this is the ceiling for New Generation heap)

3. Setting New heap size ratios
 -XX:SurvivorRatio
 The New generation area is divided into three sub-areas: Eden, and two survivor spaces that
are equal in size. 

Use the -XX:SurvivorRatio=X option to configure the ratio of the
Eden/survivor space size. Try setting this value to 8, and then monitor
your garbage collection.

4. Setting minimum heap size
 -Xms
Use this option to set the minimum size of the memory allocation pool.
Set this value to a multiple of 1024 that is greater than 1MB. As a
general rule, set minimum heap size (-Xms) equal to the maximum heap
size (-Xmx) to minimize garbage collections. 

5. Setting maximum heap size
 -Xmx
 Use this option to set the maximum Java heap size. Set this value to a multiple of 1024 that
is greater than 1MB.

i would double all specified params (leave Survivor alone) until maxheap -Xmx reaches AvailablePhysicalRam/2
2)you've maxed out HW RAM
at which point I'd run down to local tech supply store and buy more RAM sticks (good to wait
for offhours
,down the server and take one of the ram sticks with you just to make sure you have a good
fit..generally safe to double..if you have 1 get another..if you have 2 get 2 more )

(unless of course this is a unisys box then i would ask Unisys)
Martin Gainty 
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> Date: Wed, 3 Jun 2009 09:04:33 -0600
> From: John.C.Cartwright@noaa.gov
> Subject: java.net.SocketException: Too many open files
> To: users@tomcat.apache.org
> 
> Hello All,
> 
> something strange happened to our tomcat 5.5 instance running on RHEL Linux.
> 
> Suddenly we began getting the exception listed below written out to the
> catalina.out log.  It was repeated approx 4 million times w/in a couple
> of hours until it filled up the file system and hung tomcat.  This is a
> pretty standard setup.  Requests come into apache and then a ProxyPass
> forwards onto tomcat. Apache has a directive like the following for each
> context:
> 
> ProxyPass /gdsg               ajp://localhost:8009/gdsg
> 
> 
> Can someone please help to to understand what might cause such an
> exception?  Is there a good way to see the files tomcat has open?  I'm
> not sure that a simple "lsof -u tomcat" will show them all.
> 
> Thanks so much for the help!
> 
> --john
> 
> Jun 1, 2009 6:19:07 AM org.apache.jk.common.ChannelSocket acceptConnections
> WARNING: Exception executing accept
> java.net.SocketException: Too many open files
>         at java.net.PlainSocketImpl.socketAccept(Native Method)
>         at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:384)
>         at java.net.ServerSocket.implAccept(ServerSocket.java:450)
>         at java.net.ServerSocket.accept(ServerSocket.java:421)
>         at org.apache.jk.common.ChannelSocket.accept(ChannelSocket.java:312)
>         at
> org.apache.jk.common.ChannelSocket.acceptConnections(ChannelSocket.java:666)
>         at
> org.apache.jk.common.ChannelSocket$SocketAcceptor.runIt(ChannelSocket.java:876)
>         at
> org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
>         at java.lang.Thread.run(Thread.java:595)
> 
>  
> 
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