HA: don't initialize replication queues until entering Active mode
------------------------------------------------------------------
Key: HDFS-2603
URL: https://issues.apache.org/jira/browse/HDFS-2603
Project: Hadoop HDFS
Issue Type: Sub-task
Components: ha
Affects Versions: HA branch (HDFS-1623)
Reporter: Todd Lipcon
Assignee: Todd Lipcon
Priority: Critical
As described in the comments of HDFS-1975:
1) Active NN receives setReplication to drop some file's replication from 3 to 1
2) It writes OP_SET_REPLICATION to its log, invalidates two replicas, and
returns
3) The DNs report BLOCK_INVALIDATED back to both the ActiveNN and SBNN.
4) The SBNN hasn't received the OP_SET_REPLICATION yet, so it marks the block
as under-replicated.
In the case of raising replication (eg from 1 to 3) we get the opposite
problem: the SBNN marks the block as over-replicated and adds two of the
replicas to its invalidation list.
Generation stamps don't help here, because changing replication level of a
block doesn't change its gen-stamp (and it shouldn't). One possible answer is
that we need to modify FSNamesystem.isPopulatingReplQueues to return false on
the standby, and then when it switches from standby to active, initialize the
replication queues only after reading the latest edits... I think that will
solve the SET_REPLICATION issue, but not certain if it will solve all the
issues in this general class.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
