Use embedded amq brokers , no need set up any servers . It literally is one line of code to turn it on, and 5 lines of code to implement what you want.
We have a cluster of servers writing to Cassandra this way and we are not using any j2ee containers. On Thursday, January 31, 2013, Daniel Godás wrote: > Doesn't that require you to set up a server for the message queue and > know it's address? That sort of defeats the purpose of having a > database like cassandra in which all nodes are equal and there's no > single point of failure. > > 2013/1/31 Oleg Dulin <oleg.du...@liquidanalytics.com <javascript:;>>: > > Use a JMS message queue to send objects you want to write. Your writer > process then will listen on this queue and write to Cassandra. This ensures > that all writes happen in an orderly fashion, one batch at a time. > > > > I suggest ActiveMQ. It is easy to set up. This is what we use for this > type of a use case. No need to overcomplicate this with Cassandra. > > > > > > Regards, > > Oleg Dulin > > Please note my new office #: 732-917-0159 > > > > On Jan 31, 2013, at 6:35 AM, Daniel Godás <dgo...@gmail.com<javascript:;>> > wrote: > > > >> Hi all, > >> > >> I need a locking mechanism on top of cassandra so that multiple > >> clients can protect a critical section. I've seen some attempts, > >> including Dominic Williams' wait chain algorithm but I think it can be > >> simplified. This is the procedure I wrote to implement a simple mutex. > >> Note that it hasn't been thoroughly tested and I have been using > >> cassandra for a very short time so I'd appreciate any comments on > >> obvious errors or things I'm doing plain wrong and will never work. > >> > >> The assumptions and requirements for the algorithm are the same as > >> Dominic Williams' > >> ( > http://media.fightmymonster.com/Shared/docs/Wait%20Chain%20Algorithm.pdf). > >> > >> We will create a column family for the locks referred to as "locks" > >> throughout this procedure. The column family contains two columns; an > >> identifier for the lock which will also be the column key ("id") and > >> a counter ("c"). Throughout the procedure "my_lock_id" will be used as > >> the lock identifier. An arbitrary time-to-live value is required by > >> the algorithm. This value will be referred to as "t". Choosing an > >> appropriate value for "t" will be postponed until the algorithm is > >> deemed good. > >> > >> === begin procedure === > >> > >> (A) When a client needs to access the critical section the following > >> steps are taken: > >> > >> --- begin --- > >> > >> 1) SELECT c FROM locks WHERE id = my_lock_id > >> 2) if c = 0 try to acquire the lock (B), else don't try (C) > >> > >> --- end --- > >> > >> (B) Try to acquire the lock: > >> > >> --- begin --- > >> > >> 1) UPDATE locks USING TTL t SET c = c + 1 WHERE id = my_lock_id > >> 2) SELECT c FROM locks WHERE id = my_lock_id > >> 3) if c = 1 we acquired the lock (D), else we didn't (C) > >> > >> --- end --- > >> > >> (C) Wait before re-trying: > >> > >> --- begin --- > >> > >> 1) sleep for a random time higher than t and start at (A) again > >> > >> --- end --- > >> > >> (D) Execute the critical section and release the lock: > >> > >> --- begin --- > >> > >> 1) start background thread that increments c with TTL = t every t / 2 > >> interval (UPDATE locks USING TTL t SET c = c + 1 WHERE id = > >> my_lock_id) > >> 2) execute the critical section > >> 3) kill background thread > >> 4) DELETE * FROM locks WHERE id = my_lock_id > >> > >> --- end --- > >> > >> === end procedure === > >> > >> Looking forward to read your comments, > >> Dan > > > -- Sent from Gmail Mobile
