That's detailed. Thanks ATM.
On Tue, Jul 2, 2013 at 7:02 AM, Aaron T. Myers <a...@cloudera.com> wrote: > Hi Azuryy, > > On Wed, Jun 26, 2013 at 6:12 PM, Azuryy Yu <azury...@gmail.com> wrote: > > > Hi Dear all, > > > > I have some confusion for edit log retain, > > > > NNStorageRetentionManager.java: > > > > 1) > > purgeCheckpointsOlderThan() > > What's mean of check point here? > > > > Here, "checkpoint" is referring to the fsimage files on the NN. > > > > > > 2)purgeOldStorage() > > I cannot understand the calculation of minimum txid, I think I can > > understand it if I know these keys indicates. > > DFS_NAMENODE_NUM_CHECKPOINTS_RETAINED_KEY > > > > This is the number of old fsimage files to retain on the NN during purging. > > > > DFS_NAMENODE_NUM_EXTRA_EDITS_RETAINED_KEY > > > > This is the number of extra transactions to retain during purging. Here, > "extra" is referring to transactions beyond what is strictly required to > play back all FS changes since the last checkpoint (fsimage.) > > > > DFS_NAMENODE_MAX_EXTRA_EDITS_SEGMENTS_RETAINED_KEY > > > > This is the maximum number of extra edit _segments_ to retain during > purging. Segments refer to finalized edit log files, with a start and end > transaction ID. A single edit file is a "segment." > > > > > > Can any developer give me a short detail explanation? Thanks much. > > >
