Memcache on multiple servers is safe to use from multiple http servers ?

[Cristian Bichis <cristi@xxxxxxxxx>]

Hello,

I am wondering if is safe to use memcache extension with multiple 
memcache servers used from multiple http/php servers ?

I am asking this because I dont know how memcache extension is handling 
internally selecting the server where to get/set values. Because using 
multiple http servers I am not sure if for the same key all the http 
servers will query the same memcache server ?

A sample from http/php server 1:

$memcache = new Memcache;
$memcache->addServer('memcache_host1', 11211);
$memcache->addServer('memcache_host2', 11211);

$memcache_obj->set('var_key', 'value A');

echo $memcache_obj->get('var_key');

A sample from http/php server 2:

$memcache = new Memcache;
$memcache->addServer('memcache_host1', 11211);
$memcache->addServer('memcache_host2', 11211);

$memcache_obj->set('var_key', 'value B');

echo $memcache_obj->get('var_key');


We can be sure both http/php servers 1 and 2 will set/get the var_key to 
the same memcache server  ? Because otherwise it could be like this:

1. http server 1 is writing var_key to memcache_host1
2. http server 2 has an update and is writing updated var_key to 
memcache_host2
3. at a later time http server 1 is trying to get the var_key and is 
getting this from memcache_host1 => getting an outdated value ISSUE!

So how safe is to use memcache extension with multiple memcache servers 
from multiple http/php servers ?

Cristian