Please take a look at EnableTableHandler where you can find example - prepare() and process().
On Tue, Aug 9, 2016 at 5:04 PM, Liu, Ming (Ming) <ming....@esgyn.cn> wrote: > Thanks Ted for pointing out this. Can this TableLockManager be used from a > client? I am fine to migrate if this API change for each release. > I am writing a client application, and need to lock a hbase table, if this > can be used directly, that will be super great! > > Thanks, > Ming > > -----Original Message----- > From: Ted Yu [mailto:yuzhih...@gmail.com] > Sent: Wednesday, August 10, 2016 1:04 AM > To: user@hbase.apache.org > Subject: Re: help, try to use HBase's checkAndPut() to implement > distribution lock > > Please take a look at TableLockManager and its subclasses. > > It is marked @InterfaceAudience.Private > Meaning the API may change across releases. > > Cheers > > On Tue, Aug 9, 2016 at 9:58 AM, Liu, Ming (Ming) <ming....@esgyn.cn> > wrote: > > > Thanks Ted for the questions. > > > > 1. what if the process of owner of the lock dies? > > I didn't think of this... This is really an issue. I don't have a good > > answer. One possibility is to have a lease of each lock, owner must > > renew it periodically until release it. The getLock can check the last > > timestamp to see if it is expired. But I have no idea how the lock > > owner can periodic renew the lock lease, spawn a new thread to do > > that? So, this makes me trying to abandon this idea. > > > > 2. How can other processes obtain the lock? > > The getLock() has input param of table, so any process can give the > > tablename and invoke getLock(), it check the row 0 value in an atomic > > check and put operation. So if the 'table lock' is free, anyone should > > be able to get it I think. > > > > Maybe I have to study the Zookeeper's distributed lock recipes? > > > > Thanks, > > Ming > > > > -----Original Message----- > > From: Ted Yu [mailto:yuzhih...@gmail.com] > > Sent: Wednesday, August 10, 2016 12:26 AM > > To: user@hbase.apache.org > > Subject: Re: help, try to use HBase's checkAndPut() to implement > > distribution lock > > > > What if the process of owner of the lock dies ? > > How can other processes obtain the lock ? > > > > Cheers > > > > On Tue, Aug 9, 2016 at 8:19 AM, Liu, Ming (Ming) <ming....@esgyn.cn> > > wrote: > > > > > Hi, all, > > > > > > I want to implement a simple 'table lock' in HBase. My current idea > > > is for each table, I choose a special rowkey which NEVER be used in > > > real data, and then use this row as a 'table level lock'. > > > > > > The getLock() will be: > > > > > > getLock(table, cf, cl) > > > { > > > rowkey = 0 ; //which never used in real data > > > > > > //generate a UUID, thread ID + an atomic increamental sequence > > > number for example. Call it myid > > > genMyid(myid); > > > > > > while(TRUE) > > > { > > > ret = table.checkAndPut ( rowkey, cf , cl , '0' , myid); > > > if (ret == true ) get the lock > > > return myid; > > > else > > > sleep and continue; //retry, maybe can retry for > > > timeout here, or wait forever here > > > } > > > } > > > > > > The releaseLock() may be: > > > > > > releaseLock(table, cf, cl, myid) > > > { > > > Rowkey = 0; > > > ret = checkAndPut ( rowkey , cf , cl , myid , '0' ); //If I > > > am holding the lock > > > if (ret == TRUE) return TRUE; > > > else return FALSE; > > > } > > > > > > So one caller get lock, and others must wait until the caller > > > release it, and only the lock holder can release the lock. So if one > > > getLock(), it can then modify the table, others during this period > > > must > > wait. > > > > > > I am very new in lock implementation, so I fear there are basic > > > problems in this 'design'. > > > So please help me to review if there are any big issues about this > idea? > > > Any help will be very appreciated. > > > > > > Thanks a lot, > > > Ming > > > > > >
