From: Matt Triviski <matt.triviski@...>
Date: 2010-07-22T08:35:31+09:00
Subject: Writing to file delay

Hello All,

I am having a very annoying issue.  This is the situation:

I am reading a file on one machine that is continuosly being written to
and writing out to a socket.  On another machine I am reading from the
socket and writing it to a file.  The problem is that when I tail the
original file and the file I am creating, the new file has a delay of
around 1 minute until I see the new data.  It seems that the OS (Linux
Redhat 5) is waiting until it gets a block of data before it actually
writes to the file.  I want it to write immediately.

Here is a code snippet of how I am reading from the socket and writing
to the file.

file = File.new(fname, "w")
file.sync = true

buff = ""

loop{
  begin
   ios = IO.select([server.socket], [file],[server.socket, file],
0.0001)
   if ios[0].length > 0
    buff = buff + ios[0].first.readpartial(8192)
   end

   if ios[1].length > 0
    file.write buff
    buff = ""
   end

  rescue  Errno::ECONNRESET, SocketError
   puts "ERROR:  Lost connection to server"
   exit 1
  rescue EOFError
  end

  sleep 0.01
  }
}

I first used just a regular readline from the socket and then did a
file.puts line, but I was having the same issue sot that is why I tried
to go to select.  I am wondering if this is a Linux issue, since I
turned the file sync to true.  However, I am not sure, so I am hoping
that other code heads out there could help me out.
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