LOCK should be something like this:
<?php
// type=0 -> unlock
// type=1 -> lock
// client_name must change (use sessionID + username)
function memcache_flock($memcache_obj,$key,$type=0,$client_name='1',$timeout=0){
$ret=memcache_add($memcache_obj,$key,$client_name,false,$timeout);
if($ret==true){
if($type==0) // delete
memcache_del($memcache_obj,$key);
return(true);
}
$cur_cli=memcache_get($memcache_obj,$key);
if(is_string($cur_cli) && $cur_cli!=''){ // if ='' no user!
if($cur_cli !== $client_name){
// it's not our lock
if(check_user_online_function()) // http session
function (if want
http session integration), for memcached it´s like (true)
return($cur_cli); // return current lock
client_name
}
// our lock!
}else{
// replace, autocorrect a wrong usage
memcache_replace($memcache_obj, $key, $client_name, false,
$timeout);
}
if($type==0) // delete?
memcache_del($memcache_obj,$key);
return(true);
}
?>
2011/2/1 Adam Lee <a...@fotolog.biz>:
> there are some excellent solutions out there already. check out, for
> example, zookeeper.
>
> awl
>
> On Jan 29, 2011 3:32 PM, "rspadim" <rspa...@gmail.com> wrote:
>> hi guys, there's a async replication project (repcached) that is very
>> interesting, could we implement it in main source code? at compile
>> time we could select from repcached or memcached
>> could we make it sync and/or async?
>> http://repcached.sourceforge.net/
>>
>> =================================================================================
>> there's some non volatile solutions too that's very interesting
>> (memcachedb), for low memory computers we can use disk
>> could we implement it in main source code too?
>> http://memcachedb.org/
>>
>>
>> =================================================================================
>> another, now !NEW! feature...
>>
>> i was looking for a *DISTRIBUTED LOCK MANAGER*, but i only found
>> kernel linux lock manager, that's based on file system (flock)
>> could we implement a lock manager at memcached?
>>
>> what lock manager do?
>> client send: KEY NAME, lock type+client name (KEY VALUE), key timeout,
>> wait lock timeout (infinity/seconds)
>> (this can be implement in memcached protocol without many
>> modifications!!!)
>> server side function:
>> 1)seek if client can have this lock
>> 2)wait lock timeout... (this is a problem since we can have a very big
>> wait time...)
>> 3) if client disconect exit do while
>> 4) yes we have the lock => change key value (give this lock to
>> client), exit do
>> 5) no we don't have the lock, exit do
>> 6) end of do while... return key value: lock type + client name (like
>> a get command)
>>
>> ideas:
>> 1)maybe a separated memory size? we can run two separated servers, one
>> for keys another for lock function (make command line options: just
>> lock system, objects only system or both)
>>
>> 2)this type of key is diferent from memcached key cache objects,
>> that's obvious
>>
>> but........ is managed with same functions... (get, list, etc)
>> but........
>> all write/delete functions can't be done, they MUST be done by LOCK
>> (the new) function,
>> DELETE/UNLOCK function is a LOCK function with lock type=0 (unlock)
>> read can be done by get and will return current client lock name and
>> lock type (get command)
>>
>>
>>
>> *WHY THIS FEATURE?*
>> i didn't found a distributed lock manager for user space (not kernel
>> space) with easy to implement protocol, and many program languages,
>> and a very mature server and protocol.
>> =(
>>
>> but with this feature...
>> I DON'T NEED A SAMBA/NFS SERVER FOR NON FILESYSTEM LOCKING!!!!! \o/
>> I WILL NEVER USE FLOCK() AGAIN!!! \o/ !!!
>>
>> I JUST NEED:
>> MYSQL+MEMCACHED+ (APACHE+CGI/PHP/JAVA/PERL/PYTHON)
>> for any cluster solution, no more filesystem!!!
>>
>> NO MORE FILESYSTEM REPLICATIONS (DRBD, NBD+RAID) FOR MY HIGH
>> AVAIBILITY / CLUSTER SOLUTION!!!!!
>> WE CAN USE REPCACHED (WE NEED A SYNC MODE)....
>>
>> THINK ABOUT IT!!!
>> REPLICATION + FLOCK!!!!! IT'S A VERY VERY VERY NICE FEATURE!!!!!
>>
>> ====================
>> type of object (1bit) default / lock manager can be putted on key
>> options/flags!!!
>> inside key value, we can put:
>> lock type(3 bits)
>> client name (a variable length, many bytes)
>>
>> http://en.wikipedia.org/wiki/Distributed_lock_manager
>> from wikipedia, TYPE OF LOCKS:
>> * Null Lock (NL). Indicates interest in the resource, but does not
>> prevent other processes from locking it. It has the advantage that the
>> resource and its lock value block are preserved, even when no
>> processes are locking it.
>> * Concurrent Read (CR). Indicates a desire to read (but not
>> update) the resource. It allows other processes to read or update the
>> resource, but prevents others from having exclusive access to it. This
>> is usually employed on high-level resources, in order that more
>> restrictive locks can be obtained on subordinate resources.
>> * Concurrent Write (CW). Indicates a desire to read and update the
>> resource. It also allows other processes to read or update the
>> resource, but prevents others from having exclusive access to it. This
>> is also usually employed on high-level resources, in order that more
>> restrictive locks can be obtained on subordinate resources.
>> * Protected Read (PR). This is the traditional share lock, which
>> indicates a desire to read the resource but prevents other from
>> updating it. Others can however also read the resource.
>> * Protected Write (PW). This is the traditional update lock, which
>> indicates a desire to read and update the resource and prevents others
>> from updating it. Others with Concurrent Read access can however read
>> the resource.
>> * Exclusive (EX). This is the traditional exclusive lock which
>> allows read and update access to the resource, and prevents others
>> from having any access to it.
>>
>> NEW LOCK FUNCTION:
>>
>> LOCK <key><lock_type><client name><timeout><wait lock timeout>
>>
>> key: key name
>> <lock_type+client_name>=key value
>>
>> lock_type:
>> NL = 0
>> CR = 1
>> CW = 2
>> PR = 3
>> PW = 4
>> EX = 5
>>
>> client name: any value
>> timeout: any number, 0=infinity
>> wait lock timeout: wait lock time, 0=infinity
>>
>> how lock works: (see that lock type is only 0 or !=0 in this logic...)
>> i will use <sent xxxx> for user new value, and <current xxx> for the
>> current server value
>>
>> if key don't exists, create
>> do{
>> if ((sent_lock_type = 0 and sent_client_name = current_client_name)
>> or key_timed_out==1)
>> remove key (delete)
>> send null lock and sent_client_name information
>> exit function
>> }else if (sent lock type = (1 or 2 or 3 or 4 or 5), and current user
>> = sent user)
>> set
>> current_client_name,current_lock_type=sent_client_name,sent_lock_type
>> exit do
>> }else{
>> if wait lock time < time waiting lock to occur
>> exit do
>> }
>> }while(1)
>> send current_lock_type and sent_client_name
>> exit function
>>
>>
>> thanks guys!!!
>
--
Roberto Spadim
Spadim Technology / SPAEmpresarial
