[HDFS-15567] [SBN Read] HDFS should expose msync() API to allow downstream applications call it explicitly.

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.10.0
• Fix Version/s: 3.2.2, 3.3.1, 3.4.0, 2.10.2, 3.2.3
• Component/s: ha, hdfs-client
• Target Version/s: 2.10.2
• Hadoop Flags: Reviewed
• Assignee: Konstantin Shvachko
• Reporter: Konstantin Shvachko
• Created: 09/Sep/20 22:35
• Updated: 10/Jun/21 07:44
• Resolved: 13/Oct/20 01:11

Description

Consistent reads from Standby introduced msync() API HDFS-13688, which updates client's state ID with current state of the Active NameNode to guarantee consistency of subsequent calls to an ObserverNode. Currently this API is exposed via DFSClient only, which makes it hard for applications to access msync(). One way is to use something like this:

if(fs instanceof DistributedFileSystem) {
  ((DistributedFileSystem)fs).getClient().msync();
}

This should be exposed both for FileSystem and FileContext.

Issue Links

• breaks: HDFS-15639 [JDK 11] Fix Javadoc errors in hadoop-hdfs-client
• is related to: HADOOP-17477 [SBN read] Implement msync() for ViewFS
• relates to: HDFS-15751 Add documentation for msync() API to filesystem.md