[HDFS-15820] Ensure snapshot root trash provisioning happens only post safe mode exit

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.4.0
• Fix Version/s: 3.4.0
• Component/s: snapshots
• Labels: pull-request-available
• Target Version/s: 3.4.0
• Hadoop Flags: Reviewed
• Assignee: Shashikant Banerjee
• Reporter: Shashikant Banerjee
• Created: 04/Feb/21 15:17
• Updated: 12/Feb/24 01:15
• Resolved: 07/Feb/21 05:40

Description

Currently, on namenode startup, snapshot trash root provisioning starts as along with trash emptier service but namenode might not be out of safe mode by then. This can fail the snapshot trash dir creation thereby crashing the namenode. The idea here is to trigger snapshot trash provisioning only post safe mode exit.

2021-02-04 11:23:47,323 ERROR org.apache.hadoop.hdfs.server.namenode.NameNode: Error encountered requiring NN shutdown. Shutting down immediately.
org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot create directory /upgrade/.Trash. Name node is in safe mode.
The reported blocks 0 needs additional 1383 blocks to reach the threshold 0.9990 of total blocks 1385.
The number of live datanodes 0 needs an additional 1 live datanodes to reach the minimum number 1.
Safe mode will be turned off automatically once the thresholds have been reached. NamenodeHostName:quasar-brabeg-5.quasar-brabeg.root.hwx.site
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.newSafemodeException(FSNamesystem.java:1542)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkNameNodeSafeMode(FSNamesystem.java:1529)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesystem.java:3288)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkAndProvisionSnapshotTrashRoots(FSNamesystem.java:8269)
        at org.apache.hadoop.hdfs.server.namenode.NameNode$NameNodeHAContext.startActiveServices(NameNode.java:1939)
        at org.apache.hadoop.hdfs.server.namenode.ha.ActiveState.enterState(ActiveState.java:61)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:967)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:936)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1673)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1740)
2021-02-04 11:23:47,334 INFO org.apache.hadoop.util.ExitUtil: Exiting with status 1: org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot create directory /upgrade/.Trash. Name node is in safe mode.

Issue Links

• causes: HDFS-15961 standby namenode failed to start ordered snapshot deletion is enabled while having snapshottable directories
• is caused by: HDFS-15614 Initialize snapshot trash root during NameNode startup if enabled
• links to: GitHub Pull Request #2682