Question

I’ve this code in php using memcache :

<?php

$memcache = new Memcache;
$memcache->connect('localhost', 11211) or die ("Could not connect");

$version = $memcache->getVersion();
echo "Server's version: ".$version."<br/>\n";

$tmp_object = new stdClass;
$tmp_object->str_attr = 'test';
$tmp_object->int_attr = 123;

$memcache->set('key', $tmp_object, false, 1) or die ("Failed to save data at t\
he server");
echo "Store data in the cache (data will expire in 1 second)<br/>\n";
$i=0;
do{
  $get_result = $memcache->get('key');
  echo "Data from the cache:<br/>\n";
  var_dump($get_result);
  $i++;
}while($get_result);
echo $i;
var_dump($get_result);

the value of $i is different every time.. Sometimes it is 140, sometimes it is 900+, etc… Why does it change ?

edit –
btw, that is an example program for memcached from php website with minor alterations.

edit
I guess I wasn’t clear enough with question :
I meant to ask, why does the $memcache->get('key') execution takes more cpu times in some cases while it takes less cpu time in other cases.
=> more loops means $memcache->get('key') happened to take less time, less loops means it took more cpu time.
Keep in mind that cache is set to expire within 1 second and do - while executes until it expires.

Answer 1

Your loop keeps running and is reading the same key over and over again, until it is removed from memcache.

The expire time for that key is set to 1 second, so the number of times the loop runs is the number of times the value can be read in 1 second. The expire time is just an indication. It doen’t necessarily have to be 1 second exact to the millisecond. And the speed of your script can depend on various other conditions as well, so this counter isn’t very reliable.