Known Issues in HDFS

Learn about the known issues in HDFS, the impact or changes to the functionality, and the workaround.

OPSAPS-60958: The dfs.access.time.precision and dfs.namenode.accesstime.precision parameters are available in Cloudera Manager > HDFS > Configuration.
You must configure both the dfs.access.time.precision and dfs.namenode.accesstime.precision parameters with the same value as Cloudera Manager still sends both the parameters to HDFS service configuration.
ENGESC-19334: After configuring multiple NameNodes, with heavy read and write workloads in the cluster, there are chances of performance impact in terms of slowness on the client side.
This is because of the additional NN retry or probe introduced by the extra NN.
There are two solutions to mitigate the performance impact:
  • By reducing the value of the property: dfs.client.failover.sleep.base.millis // default is 500ms.
  • By increasing the value of the property dfs.client.failover.max.attempts // default is 15.
  • Using org.apache.hadoop.hdfs.server.namenode.ha.RequestHedgingProxyProvider instead of org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFailoverProxyProvider in HDFS client failover proxy provider (defined in dfs.client.failover.proxy.provider).
OPSAPS-64307: In the case when on a cluster the JournalNodes were restarted recently, the "Add new NameNode" wizard for HDFS service might fail to bootstrap the new NameNode, if there wasn't a new fsImage created since the restart of the JournalNodes, but during restarting them the edit logs were rolled in the system.
If the bootstrap fails during the "Add new NameNode" wizard, then do the following steps:
  1. Delete the newly added NameNode and FailoverController
  2. Move the active HDFS NameNode to safe mode
  3. Do a Save Namespace operation on the active HDFS NameNode
  4. Leave safe mode on the active HDFS NameNode
  5. Try to add the new NameNode again
OPSAPS-64363: Deleting of additional Standby Namenode does not delete the ZKFC role and this has to be done manually.
OPSAPS-63558: Snapshot diff based HDFS replications do not provide correct file delete and rename counters through the API.
The number of files deleted and renamed by DistCp for snapshot based replications can be checked in the logs provided by DistCp on the standard error output.
CDPD-28459: After performing an upgrade rollback from CDP 7.1.7 to CDH6, you may see the following error when restarting the DataNodes: ERROR datanode.DataNode: Exception in secureMain The path component: '/var/run/hdfs-sockets' in '/var/run/hdfs-sockets/dn' has permissions 0755 uid 39998 and gid 1006. It is not protected because it is owned by a user who is not root and not the effective user: '0'.
You must run the command described in the error message "chown root /var/run/hdfs-sockets". After this, the DataNode will restart successfully.
CDPD-28390: Rolling restart of the HDFS JournalNodes may time out on Ubuntu20.
If the restart operation times out, you can manually stop and restart the Name Node and Journal Node services one by one.
OPSAPS-60832: When decommission of DN runs for a longer time and when decommission monitor's kerberos ticket expires, it is not auto-renewed. Decommission of DN is not completed in CM as decommission monitor fails to fetch the state of DN after kerberos ticket expiry.
Decommission state of DN can be fetched using CLI command, i.e, hdfs dfsadmin -report.
OPSAPS-55788: WebHDFS is always enabled. The Enable WebHDFS checkbox does not take effect.
OPSAPS-63299: Disable HA command for a nameservice does not work if the nameservice has more than 2 NNs defined.
OPSAPS-63301: Deleting nameservice command does not delete all the NNs belonging to the nameservice, if there are more than two NNs that are assigned to the nameservice.
CDPD-50044: Data node tab loading issue in the name node UI
When clicking on the data node tab, the message NameNode is still loading. Redirecting to the Startup Progress page appears.
Unsupported Features
The following HDFS features are currently not supported in Cloudera Data Platform: