Known Issues in HDFS
Learn about the known issues in HDFS, the impact or changes to the functionality, and the workaround.
- OPSAPS-55788: WebHDFS is always enabled. The Enable WebHDFS checkbox does not take effect.
- None.
- Unsupported Features
-
The following HDFS features are currently not supported in Cloudera Data Platform:
- ACLs for the NFS gateway (HADOOP-11004)
- Aliyun Cloud Connector (HADOOP-12756)
- Allow HDFS block replicas to be provided by an external storage system (HDFS-9806)
- Consistent standby Serving reads (HDFS-12943)
- Cost-Based RPC FairCallQueue (HDFS-14403)
- HDFS Router Based Federation (HDFS-10467)
- More than two NameNodes (HDFS-6440)
- NameNode Federation (HDFS-1052)
- NameNode Port-based Selective Encryption (HDFS-13541)
- Non-Volatile Storage Class Memory (SCM) in HDFS Cache Directives (HDFS-13762)
- OpenStack Swift (HADOOP-8545)
- SFTP FileSystem (HADOOP-5732)
- Storage policy satisfier (HDFS-10285)
Technical Service Bulletins
- TSB 2023-666: Out of order HDFS snapshot deletion may delete renamed/moved files, which may result in data loss
- Cloudera has discovered a bug in the Apache Hadoop Distributed File
System (HDFS) snapshot implementation. Deleting an HDFS snapshot may
incorrectly remove files in the
.Trash
directories or remove renamed files from the current file system state. This is an unexpected behavior because deleting an HDFS snapshot should only delete the files stored in the specified snapshot, but not data in the current state. - Components affected
- HDFS
- Products affected
-
- Cloudera Data Platform (CDP)
- Cloudera Distribution including Apache Hadoop (CDH)
- Hortonworks Data Platform (HDP)
- Releases affected
-
- CDP Private Cloud Base 7.1.7 SP2 CHF6 and earlier; 7.1.8 CHF7 and earlier
- All versions of CDP Public Cloud
- All versions of CDH
- All versions of HDP
- Users affected
- Cloudera customers using the HDFS snapshot feature.
- Impact
- When the files are removed incorrectly by deleting a snapshot, the
standby namenode checkpoint (or the namenode checkpoint for non-High
Availability clusters) fails with missing INode file and the namenode
shuts down with a “Missing INode” error message in the logs as shown in
the example below. This can result in data loss as the current file data
stored in HDFS can be removed incorrectly when deleting a HDFS
snapshot.
2023-04-14 10:04:11,175 [FSImageSaver for /grid/1/dfs/namenode/current of type IMAGE_AND_EDITS] ERROR namenode.FSImage (FSImageFormatPBINode.java:serializeINodeDirectorySection(765)) - FSImageFormatPBINode#serializeINodeDirectorySection: Dangling child pointer found. Missing INode in inodeMap: id=154614; path=/user/foo/.Trash/Current/file; parent=/user/foo/.Trash/Current
- Severity
- High
- Action required
-
- Risk Avoidance:
- When deleting multiple snapshots, delete them in order: from the earliest to the latest. This will reduce the risk of data loss as it is a proven experience that deleting the earliest snapshot in the file system will not cause data loss.
- To determine the snapshot creation order, use the
hdfs lsSnapshot <snapshotDir>
command, and then sort the output by the snapshot ID. - If snapshot A is created earlier than snapshot B, the
snapshot ID of A is smaller than the snapshot ID of B. The
following is the output format of
lsSnapshot
:<permission> <replication> <owner> <group> <length> <modification_time> <snapshot_id> <deletion_status> <path>
- Upgrade (Highly Recommended)
- CDH / HDP / CDP Private Cloud Base customers should upgrade to the CDP Private Cloud Base7.1.7 Service Pack (SP) 2 Cumulative Hotfix (CHF) 10 or CDP Private Cloud Base 7.1.8 Cumulative Hotfix (CHF) 10 or later.
- Upcoming CDP Public Cloud Service Pack releases will include the fixes
- Hotfixes (if any)
CDH or HDP customers should upgrade to one of the fixed CDP releases mentioned above or contact support to request a hotfix for HDFS-16972, HDFS-16975, and HDFS-17045.
- Knowledge article
For the latest update on this issue see the corresponding Knowledge article: TSB 2023-666: Out of order HDFS snapshot deletion may delete renamed/moved files, which may result in data loss
- Risk Avoidance: