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stack edited comment on HBASE-8741 at 8/6/13 1:28 PM: ------------------------------------------------------ Region is redundant in RegionSequenceIds since SequenceIds are per Region always when this patch applied. was (Author: stack): I Region redundant in RegionSequenceIds since SequenceIds are per Region always when this patch applied. > Mutations on Regions in recovery mode might have same sequenceIDs > ----------------------------------------------------------------- > > Key: HBASE-8741 > URL: https://issues.apache.org/jira/browse/HBASE-8741 > Project: HBase > Issue Type: Bug > Components: MTTR > Affects Versions: 0.95.1 > Reporter: Himanshu Vashishtha > Assignee: Himanshu Vashishtha > Fix For: 0.95.2 > > Attachments: HBASE-8741-v0.patch, HBASE-8741-v2.patch, > HBASE-8741-v3.patch, HBASE-8741-v4-again.patch, HBASE-8741-v4-again.patch, > HBASE-8741-v4.patch > > > Currently, when opening a region, we find the maximum sequence ID from all > its HFiles and then set the LogSequenceId of the log (in case the later is at > a small value). This works good in recovered.edits case as we are not writing > to the region until we have replayed all of its previous edits. > With distributed log replay, if we want to enable writes while a region is > under recovery, we need to make sure that the logSequenceId > maximum > logSequenceId of the old regionserver. Otherwise, we might have a situation > where new edits have same (or smaller) sequenceIds. > We can store region level information in the WALTrailer, than this scenario > could be avoided by: > a) reading the trailer of the "last completed" file, i.e., last wal file > which has a trailer and, > b) completely reading the last wal file (this file would not have the > trailer, so it needs to be read completely). > In future, if we switch to multi wal file, we could read the trailer for all > completed WAL files, and reading the remaining incomplete files. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira