I would strongly discourage people from building on top of lockRow/unlockRow. The problem is if a row is not available, lockRow will hold a responder thread and you can end up with a deadlock because the lock holder won't be able to unlock. Sure the expiry system kicks in, but 60 seconds is kind of infinity in database terms :-)
I would probably go with either ICV or CAS to build the tools you want. With CAS you can accomplish a lot of things locking accomplishes, but more efficiently. On Wed, Apr 28, 2010 at 9:42 AM, Stack <st...@duboce.net> wrote: > Would the incrementValue [1] work for this? > St.Ack > > 1. > http://hadoop.apache.org/hbase/docs/r0.20.3/api/org/apache/hadoop/hbase/client/HTable.html#incrementColumnValue%28byte[],%20byte[],%20byte[],%20long%29 > > On Wed, Apr 28, 2010 at 7:40 AM, Tatsuya Kawano > <tatsuy...@snowcocoa.info> wrote: >> Hi, >> >> I'd like to implement unique row ID constraint (like the primary key >> constraint in RDBMS) in my application framework. >> >> Here is a code fragment from my current implementation (HBase >> 0.20.4rc) written in Scala. It works as expected, but is there any >> better (shorter) way to do this like checkAndPut()? I'd like to pass >> a single Put object to my function (method) rather than passing rowId, >> family, qualifier and value separately. I can't do this now because I >> have to give the rowLock object when I instantiate the Put. >> >> =============================================== >> def insert(table: HTable, rowId: Array[Byte], family: Array[Byte], >> qualifier: Array[Byte], value: >> Array[Byte]): Unit = { >> >> val get = new Get(rowId) >> >> val lock = table.lockRow(rowId) // will expire in one minute >> try { >> if (table.exists(get)) { >> throw new DuplicateRowException("Tried to insert a duplicate row: " >> + Bytes.toString(rowId)) >> >> } else { >> val put = new Put(rowId, lock) >> put.add(family, qualifier, value) >> >> table.put(put) >> } >> >> } finally { >> table.unlockRow(lock) >> } >> >> } >> =============================================== >> >> Thanks, >> >> -- >> 河野 達也 >> Tatsuya Kawano (Mr.) >> Tokyo, Japan >> >> twitter: http://twitter.com/tatsuya6502 >> >
