Yes!! So is there any locking mechanisms? Plus what dictates this delay in file deletion and actual deletion of the file blocks over the cluster?
regards, On Fri, Mar 14, 2008 at 6:22 AM, edward yoon <[EMAIL PROTECTED]> wrote: > Can zookeeper locking services be used for these cases? > > Thanks, > Edward. > > On 3/13/08, Sanjay Radia <[EMAIL PROTECTED]> wrote: > > Ahmad Humayun wrote: > > > So does that mean nodes can possibly read files that have been > "deleted" > > > > > If the name node entry has been deleted, new opens will fail. > > Already opened files may have their reads succeed if they have cached > > the block locations and also if the > > blocks have not been deleted. > > > > Hence, if you open a large file and someone deletes the file after you > > open it, at some point the reads may fail if > > the client needs to go to the namenode to get block locations. > > This not posix semantics but keeping the namenode stateless has > > advantages in scaling. > > > thanks :) > > > > > > > > > regards, > > > > > > On Wed, Mar 12, 2008 at 10:57 PM, Hairong Kuang <[EMAIL PROTECTED] > > > > > wrote: > > > > > > > > >>> Case 1: Lets say there is a node which opens a file on the DFS to > read. > > >>> > > >> From > > >> > > >>> my understanding, the open request will go to the namenode, which > will > > >>> > > >> tell > > >> > > >>> it where the blocks of the file are. What if another node comes up > and > > >>> > > >> asks > > >> > > >>> to delete that file. Of course this request will go to the namenode. > How > > >>> will the namenode respond in such a situation? > > >>> > > >>> > > >> The namenode is stateless. So the delete request will go through. The > > >> first > > >> request may fail. > > >> > > >> > > >>> Case 2: Whenever a node wants to delete a file, I think the request > > >>> > > >> first > > >> > > >>> lands with the namenode? What happens to the replicas of the blocks > of > > >>> > > >> that > > >> > > >>> file, as soon as that file gets deleted? > > >>> > > >>> > > >> The replicas are scheduled to be deleted by the namenode. But there > may be > > >> some delay before they are actually deleted on the datanodes. > > >> > > >> Hairong > > >> > > >> > > >> > > > > > > > > > > > > > > > > -- > B. Regards, > Edward yoon @ NHN, corp. > -- Ahmad Humayun Research Assistant Computer Science Dpt., LUMS +92 321 4457315
