Open Mash Cross Reference
mash/tcl/srmv2-cache/cache-timer.tcl

   # cache-timer.tcl --
   #
   #       FIXME: This file needs a description here.
   #
   # Copyright (c) 1998-2002 The Regents of the University of California.
   # All rights reserved.
   #
   # Redistribution and use in source and binary forms, with or without
   # modification, are permitted provided that the following conditions are met:
  #
  # A. Redistributions of source code must retain the above copyright notice,
  #    this list of conditions and the following disclaimer.
  # B. Redistributions in binary form must reproduce the above copyright notice,
  #    this list of conditions and the following disclaimer in the documentation
  #    and/or other materials provided with the distribution.
  # C. Neither the names of the copyright holders nor the names of its
  #    contributors may be used to endorse or promote products derived from this
  #    software without specific prior written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS''
  # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  # ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
  # ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  # SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  # OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  import Timer/Adaptive
  
  #
  # A binary exponential backoff timer.
  #
  Class Timer/Adaptive/Backoff -superclass Timer/Adaptive
  
  #
  # The binary exponential backoff timer constructor. The arguments
  # <i>c1</i>, <i>c2</i> and <d> control the backoff like this:
  # [c1*d, (c1+c2)*d].
  #
  Timer/Adaptive/Backoff public init { c1 c2 d app } {
          $self instvar c1_ c2_ d_ app_ i_
  
          set c1_ $c1
          set c2_ $c2
          set d_ $d
          set app_ $app
          set i_ 0
  
          $self next
          $self start
  }
  
  #
  # Do a binary exponential backoff of the current timer value.
  #
  Timer/Adaptive/Backoff private adapt { interval } {
          $self instvar id_ c1_ c2_ d_ i_
  
          set t [expr pow(2,$i_) * ([random]/double(0x7fffffff) * ($c2_*$d_) + ($c1_*$d_))]
          incr i_
          return $t
  }
  
  #
  # Called when need to backoff the current timer.
  #
  Timer/Adaptive/Backoff public backoff { } {
          $self instvar i_
  
          # schedule the next backoff, and start implicitly call cancel
          # if required
          incr i_
          $self start
  }
  
  #
  # A url get timer which is backoff exponentially.
  #
  Class URL_Get_Timer -superclass Timer/Adaptive/Backoff
  
  #
  # The url get timer constructor.
  #
  URL_Get_Timer public init { url c1 c2 d app } {
          $self instvar url_
          set url_ $url
  
          $self next $c1 $c2 $d $app
  }
  
  #
  # Called when the timer timeouts. This first does a callback
  # to the web cache control so it can notify other caches that
  # it has won the get timer war, and then backoff the get timer.
  #
  URL_Get_Timer public timeout { } {
         $self instvar url_ app_
 
         # do a callback to the application
         $app_ send_announcement WC_URL_GET $url_
 }
 
 #
 # A url response timer which is backoff exponentially.
 #
 Class URL_Resp_Timer -superclass Timer/Adaptive/Backoff
 
 #
 # The url response timer constructor.
 #
 URL_Resp_Timer public init { url c1 c2 d app } {
         $self instvar url_
         set url_ $url
 
         $self next $c1 $c2 $d $app
 }
 
 URL_Resp_Timer public destroy { } {
         $self instvar url_
         #puts "destroy URL_Resp_Timer $url_ $self"
         $self next
 }
 
 #
 # Called when the timer timeouts. This does a callback to
 # the web cache control so it can notify other caches that
 # it is going to send the contents of the url to the session.
 #
 URL_Resp_Timer public timeout { } {
         $self instvar url_ app_
 
         #puts "wcc: win_resp_timer $url_ $self"
 
         # send out the data or do a HTTP request to the origin server
         $app_ win_resp_timer $url_
 }