I created a script for use with my website that is supposed to erase the oldest entry in cache when a new item needs to be cached. My website is very large with 500,000 photos on it and the cache space is set to 2 GB.
These functions are what cause the trouble:
function cache_tofile($fullf, $c)
{
error_reporting(0);
if(strpos($fullf, "/") === FALSE)
{
$fullf = "./".$fullf;
}
$lp = strrpos($fullf, "/");
$fp = substr($fullf, $lp + 1);
$dp = substr($fullf, 0, $lp);
$sz = strlen($c);
cache_space_make($sz);
mkdir($dp, 0755, true);
cache_space_make($sz);
if(!file_exists($fullf))
{
$h = @fopen($fullf, "w");
if(flock($h, LOCK_EX))
{
ftruncate($h, 0);
rewind($h);
$tmo = 1000;
$cc = 1;
$i = fputs($h, $c);
while($i < strlen($c) || $tmo-- > 1)
{
$c = substr($c, $i);
$i = fwrite($h, $c);
}
flock($h, LOCK_UN);
fclose($h);
}
}
error_reporting(7);
}
function cache_space_make($sz)
{
$ct = 0;
$cf = cachefolder();
clearstatcache();
$fi = shell_exec("df -i ".$cf." | tail -1 | awk -F\" \" '{print \$4}'");
if($fi < 1)
{
return;
}
if(($old = disk_free_space($cf)) === false)
{
return;
}
while($old < $sz)
{
$ct++;
if($ct > 10000)
{
error_log("Deleted over 10,000 files. Is disk screwed up?");
break;
}
$fi = shell_exec("rm \$(find ".$cf."cache -type f -printf '%T+ %p\n' | sort | head -1 | awk -F\" \" '{print \$2}');");
clearstatcache();
$old = disk_free_space($cf);
}
}
cachefolder() is a function that returns the correct folder name with a / appended to it.
When the functions are executed, the CPU usage for apache is between 95% and 100% and other services on the server are extremely slow to access during that time. I also noticed in whm that cache disk usage is at 100% and refuses to drop until I clear the cache. I was expecting more like maybe 90ish%.
What I am trying to do with the cache_tofile function is attempt to free disk space in order to create a folder then free disk space to make the cache file. The cache_space_make function takes one parameter representing the amount of disk space to free up.
In that function I use system calls to try to find the oldest file in the directory tree of the entire cache and I was unable to find native php functions to do so.
The cache file format is as follows:
/cacherootfolder/requestedurl
For example, if one requests http://www.example.com/abc/def then from both functions, the folder that is supposed to be created is abc and the file is then def so the entire file in the system will be:
/cacherootfolder/abc/def
If one requests http://www.example.com/111/222 then the folder 111 is created and the file 222 will be created
/cacherootfolder/111/222
Each file in both cases contain the same content as what the user requests based on the url. (example: /cacherootfolder/111/222 contains the same content as what one would see when viewing source from http://www.example.com/111/222)
The intent of the caching system is to deliver all web pages at optimal speed.
My question then is how do I prevent the system from trying to lockup when the cache is full. Is there better code I can use than what I provided?