[jira] [Created] (HDFS-5080) BootstrapStandby not working with QJM when the existing NN is active

["Jing Zhao (JIRA)" <ji...@apache.org>]

Jing Zhao created HDFS-5080:
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             Summary: BootstrapStandby not working with QJM when the existing NN is active
                 Key: HDFS-5080
                 URL: https://issues.apache.org/jira/browse/HDFS-5080
             Project: Hadoop HDFS
          Issue Type: Bug
    Affects Versions: 3.0.0
            Reporter: Jing Zhao
            Assignee: Jing Zhao


Currently when QJM is used, running BootstrapStandby while the existing NN is active can get the following exception:
{code}
FATAL ha.BootstrapStandby: Unable to read transaction ids 6175397-6175405 from the configured shared edits storage. Please copy these logs into the shared edits storage or call saveNamespace on the active node.
Error: Gap in transactions. Expected to be able to read up until at least txid 6175405 but unable to find any edit logs containing txid 6175405
java.io.IOException: Gap in transactions. Expected to be able to read up until at least txid 6175405 but unable to find any edit logs containing txid 6175405
	at org.apache.hadoop.hdfs.server.namenode.FSEditLog.checkForGaps(FSEditLog.java:1300)
	at org.apache.hadoop.hdfs.server.namenode.FSEditLog.selectInputStreams(FSEditLog.java:1258)
	at org.apache.hadoop.hdfs.server.namenode.ha.BootstrapStandby.checkLogsAvailableForRead(BootstrapStandby.java:229)
{code}

Looks like the cause of the exception is that, when the active NN is queries by BootstrapStandby about the last written transaction ID, the in-progress edit log segment is included. However, when journal nodes are asked about the last written transaction ID, in-progress edit log is excluded. This causes BootstrapStandby#checkLogsAvailableForRead to complain gaps. 

To fix this, we can either let journal nodes take into account the in-progress editlog, or let active NN exclude the in-progress edit log segment.

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