[HDFS-7473] Document setting dfs.namenode.fs-limits.max-directory-items to 0 is invalid

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.0, 2.5.2
• Fix Version/s: 2.7.0
• Component/s: documentation
• Labels: newbie
• Target Version/s: 2.7.0
• Hadoop Flags: Reviewed
• Assignee: Akira Ajisaka
• Reporter: Jason Keller
• Created: 04/Dec/14 21:51
• Updated: 10/Apr/15 20:29
• Resolved: 08/Dec/14 19:09

Description

When setting dfs.namenode.fs-limits.max-directory-items to 0 in hdfs-site.xml, the error "java.lang.IllegalArgumentException: Cannot set dfs.namenode.fs-limits.max-directory-items to a value less than 0 or greater than 6400000" is produced. However, the documentation shows that 0 is a valid setting for dfs.namenode.fs-limits.max-directory-items, turning the check off.

Looking into the code in hadoop/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java shows that the culprit is

Preconditions.checkArgument(maxDirItems > 0 && maxDirItems <= MAX_DIR_ITEMS, "Cannot set "+ DFSConfigKeys.DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY+ " to a value less than 0 or greater than " + MAX_DIR_ITEMS);

This checks if maxDirItems is greater than 0. Since 0 is not greater than 0, it produces an error.

Issue Links

• relates to: HDFS-6102 Lower the default maximum items per directory to fix PB fsimage loading