thanks very much wt: Your answer definitely answer my interrogations !
fengguang 在 2013-9-16，下午4:05，Warren Turkal <[email protected]> 写道： > I must not understand your question fully as cases (1) and (2) look very > similar. It looks like you are trying to provide "atomic" access to the > data in both cases. It looks like case (2) is a special case of case (1) in > that only one of the processes is allowed to access the node and delete it. > > If my understanding above is correct, you may be able to do the following > for case (1). You can make your processes coordinate by using a distributed > lock (implemented using ZK) to guard access to the node. Once you have the > lock, you can do whatever you want to the node without fear that others are > acting on it. You can find example lock code in the ZK > docs<http://zookeeper.apache.org/doc/r3.4.5/recipes.html#sc_recipes_Locks>or > you could use the Curator > lib <https://github.com/Netflix/curator> to implement the lock. > > As for case (2), you don't need a lock since only one process is allowed to > access it. You could create the node name with a pattern such that you know > it should only be processed by process4. For example, you might have the > following hierarchy of znodes: > > - /myapp > - /myapp/case1nodes > - /myapp/case2nodes > > Process4 and your other processes would know that only process4 is allowed > to process nodes in /myapp/case2nodes. > > If you need to elect a process to be "process4", you can use ZK to > implement an election (see this > link<http://zookeeper.apache.org/doc/r3.4.5/recipes.html#sc_leaderElection> > for > a ZK recipe). > > wt > > > On Sun, Sep 15, 2013 at 10:27 PM, fengguang gong > <[email protected]>wrote: > >> Hi all： >> when a znode is updated, there are four processes(1.2.3.4)can access the >> znode. >> Two cases: >> (1)what i need is that there is only one process execute getData and >> delete atomically. >> (2)what i need is that process4 execute getData and delete atomically. >> In case (1), EPHEMERAL_SEQUENTIAL will be used. >> In case (2), what should i do?
