[Rt-devel] [PATCH] Callback stat cache

[Matt Mankins]

In doing some profiling someone noticed a bunch of stats looking for 
Callback modifications.  In the "every little bit counts" category, this 
patch caches the stat/response so that subsequent requests can use the 
in-memory response rather than go out and get the fresh value via a system 
call.

If I understand it correctly, on production systems, it should be a rare
event that new Callbacks are added.  If they are added, the sysadmin could
certainly restart RT to make them show up.  

I added this to my RT_Siteconfig:

# Callback Timeout
# Seconds until the callback cache times out Set this high (86400) for 
# production systems, low for development (0) [default]

Set($CallbackTimeout, 10000);

.
.
.
And it seems to have made some difference, although I haven't run any 
tests to verify.

This obviously only makes sense in persistent environments.

Let me know if you see any booboos/comments/etc.

Matt Mankins
http://www.loremipsumbooks.com/
-------------- next part --------------
*** html/Elements/Callback	Sun Mar 28 04:04:08 2004
--- /tmp/Callback	Fri Sep 17 19:12:53 2004
***************
*** 25,37 ****
  my (%cache, $check);
  </%once>
  <%init>
! # checks for inode change time for each callback directory
! my $new_check = join(
!     $;, map { $_->[1] => (stat("$_->[1]/Callbacks"))[10] } $m->interp->resolver->comp_root_array
! ) or return;
  
  $Page = $m->callers(1)->path unless ($Page);
  
  my $callbacks;
  if ($new_check eq $check) {
      $callbacks = $cache{$Page,$_CallbackName};
--- 25,56 ----
  my (%cache, $check);
  </%once>
  <%init>
! my $callback_timeout = $RT::CallbackTimeout || 0; # seconds.  
! 
! my $new_check;
! my $start_time = time;
  
  $Page = $m->callers(1)->path unless ($Page);
  
+ if ( ( $start_time - ($RT::Callback::cache{$Page.$_CallbackName."time"}) ) > $callback_timeout)
+ {
+   # Stat Cache miss, do the stat
+ 
+   # checks for inode change time for each callback directory
+   $new_check = join(
+       $;, map { $_->[1] => (stat("$_->[1]/Callbacks"))[10] } $m->interp->resolver->comp_root_array
+   ) or return;
+ 
+   # set the stat cache
+   $RT::Callback::cache{$Page.$_CallbackName."time"} = $start_time;
+   $RT::Callback::cache{$Page.$_CallbackName} = $new_check;
+ }
+ else
+ {
+   # we'll use our stat cache instead of stat'ing
+   $new_check = $RT::Callback::cache{$Page.$_CallbackName};
+ }
+ 
  my $callbacks;
  if ($new_check eq $check) {
      $callbacks = $cache{$Page,$_CallbackName};
***************
*** 49,56 ****
      my $invalid_base = "/Callbacks/$Page/$_CallbackName";
      @$callbacks = grep !/^$invalid_base$/, @$callbacks;
  
- 
- 
      $cache{$Page,$_CallbackName} = $callbacks;
  }
  
--- 68,73 ----