[ https://issues.apache.org/jira/browse/HBASE-23205?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Work on HBASE-23205 started by Jeongdae Kim. -------------------------------------------- > Correctly update the position of WALs currently being replicated. > ----------------------------------------------------------------- > > Key: HBASE-23205 > URL: https://issues.apache.org/jira/browse/HBASE-23205 > Project: HBase > Issue Type: Bug > Affects Versions: 1.5.0, 1.4.10, 1.4.11 > Reporter: Jeongdae Kim > Assignee: Jeongdae Kim > Priority: Major > > We observed a lot of old WALs were not removed from archives and their > corresponding replication queues, while testing with 1.4.10. > stacked old WALs are empty or have no entries to be replicated (not in > replication table_cfs) > > As described in HBASE-22784, if no entries to be replicated are appended to > WALs, log position will never be updated. As a consequence, all WALs won’t be > removed. this issue happened since HBASE-15995. > > I think old WALs would not be stacked with HBASE-22784. but, it still have > something to be fixed as below > * log position could be updated wrongly, when log rolled, because > lastWalPath of batches might not point to WAL currently being read. > ** For example, after last entries to be added in batch was read from P1 > position in the WAL W1 > and then WAL rolled, and reader read until it reaches the end of old wals > and continue reading entries from new WAL W2, and then it reached batch size. > current read position for W2 is P2. In this case, the batch being passed to a > shipper have walPath W1 and P2, so shipper will try to update position P2 for > W1. it may result in data inconsistency in recovery case or update failure to > zookeeper (znode could not exist by previous log position updates, i guess > this case is the same case asHBASE-23169?) > * log position could be not updated or updated to wrong position by > pendingShipment flag introduced from HBASE-22784 > ** In shipper thread, it would not beguaranteed to update log position > always by setting pendingShipment to false. > If reader set the flag to true, right after shipper set it to false during > {color:#24292e}updateLogPosition(), shipper won’t update log position.{color} > On the other hand, while reader read filtered entries, If shipper set to > false reader will update log position to current read position. it may lose > data in recovery case. > * a lot of log position updates could be happened, when most of WAL entries > are filtered by TableCfWALEntryFilter. > ** I think it would be better to reduce the number of log updates in that > case, because > ### zookeeper writes are more expensive operations than reads.(since writes > involve synchronizing the state of all servers), > ### even if read position was not updated, it would be harmless because all > entries will be filtered out again in recovery process. > I think it's enough to update log position only when wal rolled in that > case. (to cleanup old wals) > > In addition, During this work, i found a minor bug which is updating > replication buffer size wrongly by decreasing total buffer size with the size > of bulk loaded files. > I’d like to fix it, if it’s ok. -- This message was sent by Atlassian Jira (v8.3.4#803005)