ok, but it´s client based...
i want a server based (memcache daemon)
at client side:
memcached_lock("lock_name",1);
memcached_lock("lock_name",0);
at server side:
lock/unlock some variable (maybe a server based flock())
since we use ram memory we could use ram locks (not filesystem lock)
with repcache we can replicate this lock on replicas....
2011/2/3 Adam Lee <a...@fotolog.biz>:
> Here's one I hacked together a while back, though, as I said before, I
> recommend using something better suited to the job... BTW, this thing uses
> a few of our utility classes, but it should be very simple to drop in
> replacements.
> public class GlobalLock
> {
> public GlobalLock(String lockType, String resourceId)
> {
> if (StringUtils.isBlank(lockType))
> throw new NullPointerException("Empty lock type");
> if (StringUtils.isBlank(resourceId))
> throw new NullPointerException("Empty resource id");
> _globalId = StringUtil.toHexString((lockType +
> resourceId).getBytes()) +":GlobalLock";
> while(_value == 0)
> _value = RandomUtils.nextLong();
> _acquired = false;
> }
> public GlobalLock lock()
> {
> if (_acquired)
> return this;
> // Lock duration 20sec
> // tries to acquire lock for 21sec
> // obviously this is a far from perfect hack
> final int LOCK_DURATION_SECS = 20;
> final int SLEEP_TIME_MILLIS = 100;
> final int MAX_TRIES = 210; // max number of attempts to acquire lock
> MemcachedClient mc = FotologMemCache.getFotolog();
> for(int numTries = 0; numTries < MAX_TRIES; numTries++)
> {
> if (_log.isInfoEnabled()) _log.info("locking "+_globalId);
> try
> {
> CASValue<Object> mcVal = mc.gets(_globalId);
> if (mcVal == null)
> {
> _acquired = mc.add(_globalId, LOCK_DURATION_SECS,
> _value).get();
> }
> else if ( ((Long)mcVal.getValue()).longValue() == 0 )
> {
> CASResponse casResp = mc.cas(_globalId, mcVal.getCas(),
> _value);
> _acquired = (casResp == CASResponse.OK);
> }
> else
> {
> if (_log.isInfoEnabled()) _log.info("waiting for another
> process to finish: "+_globalId + ":" + mcVal.getValue());
> }
> }
> catch (Exception e)
> {
> _log.error(e.getMessage());
> }
> if (_acquired)
> return this;
> try { Thread.sleep(SLEEP_TIME_MILLIS); } catch
> (InterruptedException ie) {/**/} // don't 'busywait'
> }
> throw new GlobalLockException("Unable to lock [" + _globalId + "]
> after " + MAX_TRIES + " attempts");
> }
>
> /** Unlocks ALL of the resources locked with lock().
> * Never fails, so doesn't require additional try/catch if you are
> calling it from some other 'finally'
> */
> public void unlock()
> {
> if (_acquired)
> {
> _acquired = false;
> MemcachedClient mc = FotologMemCache.getFotolog();
> CASValue<Object> mcVal = mc.gets(_globalId);
> if (mcVal == null)
> {
> // nothing to do, val already expired
> if (_log.isInfoEnabled()) _log.info("already expired: " +
> _globalId + ":" + _value);
> return;
> }
> else if ( ((Long)mcVal.getValue()).longValue() == _value )
> {
> mc.cas(_globalId, mcVal.getCas(), 0l); // reset but only if
> it matches our val
> }
> else
> {
> _log.error("failed to unlock: " + _globalId + ":" + _value);
> }
> }
> }
>
> private static Logger _log = Logger.getLogger(GlobalLock.class);
> private String _globalId;
> private long _value;
> private boolean _acquired;
> }
> On Tue, Feb 1, 2011 at 1:40 PM, Roberto Spadim <robe...@spadim.com.br>
> wrote:
>>
>> 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
>
>
>
> --
> awl
>
--
Roberto Spadim
Spadim Technology / SPAEmpresarial
