Re: Memcache session handler

Hi,

I'm glad I found this feature. I had just started writing my own session 
handler functions for memcache but then I found this.

However, I need to know what happens when the whole server pool is down?
I purposely stopped all my memcache servers but sessions are still working 
just fine with storing and updating data.

Where are the sessions being stored? Theres nothing in /tmp

Thanks.


"Mikael Johansson" <mikael@xxxxxxxxx> wrote in message 
news:454147F0.4070406@xxxxxxxxxxxx
> The CVS version of pecl/memcache now has session support, you may check
> out and build a copy as
>
> cvs -d :pserver:cvsread@xxxxxxxxxxx:/repository checkout pecl/memcache
> cd pecl/memcache
> phpize
> ./configure
> make
> make install
>
> The session save handler is activated from INI as
>
> session.save_handler = memcache
> session.save_path =
> "tcp://host1:11211?persistent=1&weight=2,tcp://host2:11211"
>
> The parameters accepted on the url are "persistent", "weight", "timeout"
> and "retry_interval" (same as to Memcache::addServer().) You may add any
> number of servers separated by commas. The new unix domain socket
> feature may also be used as "unix:///path/to/memcache.sock:0"
>
> Feedback and help with testing would be most appreciated.
>
> //Mikael
>
> Glenn Richmond wrote:
>> Hi Mickael & Antony,
>>
>> I've attached the key session handling code for the memcache handler. It
>> uses libmemcache as the back end, so naturally the function calls will
>> be slightly different when adding to the memcache extension. At the
>> moment, I configure the system in the php.ini with the following 
>> settings:
>>
>> session.save_handler="memcache"
>> session.memcache_server_1="xxx:xxx:xxx:xxx:11211"
>> session.memcache_server_2="xxx:xxx:xxx:xxx:11211"
>>
>> At the moment, the first server is compulsory,  but the second is
>> optional. I integrated it directly with the standard files and user
>> session handlers initially just to test the theory, but we should be
>> able to separate now i think. Let me know what your thoughts are -
>> whether you want me to have a go at integrating it or if you want to
>> take the existing code and just port it.
>>
>> Best Regards,
>>
>> Glenn Richmond.
>>
>> Mikael Johansson wrote:
>>> I agree with Antony, there shouldn't be a problem integrating session
>>> handling into pecl/memcache. Some questions though
>>>
>>>  * The extension needs to know the address of the servers in order to
>>> connect, so how do you start the session?
>>>
>>>   1) From php.ini using something like
>>>
>>>   memcache.session_storage =
>>> "tcp://node01.example.com:11211?weight=2,tcp://node02.example.com:11211"
>>>   session.save_handler = memcache
>>>
>>>   2) From your script as
>>>
>>>   $memcache = new Memcache();
>>>   $memcache->addServer(...);
>>>   $memcache->registerSessionHandler();
>>>   session_start();
>>>
>>>  * Memcache (as with any other cache) is inherently unreliable and might
>>> garbage collect keys in a LRU fashion should it need the memory for
>>> other keys. One might be able to mitigate this issue by ensuring that
>>> memcache has plenty memory, but until there's a (per key) DO_NOT_GC flag
>>> implemented in memcached there's always the risk of sessions being 
>>> dropped.
>>>
>>> Better to have a 2-tier session storage where writes are passed through
>>> to a database (shared by all the web front ends) and reads are handled
>>> by the cache. For example:
>>>
>>>   http://svn.synd.info/synd/trunk/core/lib/SessionHandler.class.inc
>>>
>>> But if you need the performance of storing the session only in memcached
>>> and are aware of the potential problems, you should be able to do so.
>>>
>>> If you wouldn't mind posting a link to your code and a patch against the
>>> current CVS head we'll try and integrate it as soon as possible.
>>>
>>> //Mikael
>>>
>>> Glenn Richmond wrote:
>
> [snip]