hbase-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Liu, Ming (Ming)" <ming....@esgyn.cn>
Subject RE: help, try to use HBase's checkAndPut() to implement distribution lock
Date Wed, 10 Aug 2016 00:04:18 GMT
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:yuzhihong@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.liu@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:yuzhihong@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.liu@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
> >
>
Mime
View raw message