[HADOOP-10080] Variables in configuration properties are substituted in wrong order of precedence

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 2.2.0
• Component/s: conf
• Assignee: Unassigned
• Reporter: Sebastian Nagel
• Created: 01/Nov/13 15:44
• Updated: 07/Nov/13 16:48

Description

API doc of Configuration states:

Value strings are first processed for variable expansion. The available properties are:
1. Other properties defined in this Configuration; and, if a name is undefined here,
2. Properties in System.getProperties().

The current implementation of variable expansion, however, gives precedence to system properties. If a system property is defined it's value is used no matter whether a configuration property of same name exists.
This may cause inconsistent behaviour, e.g., if in the API doc example "basedir" is set as system property (-Dbasedir=/mnt/tmp) the results of two intuitively equivalent calls differ:

 new Path(conf.get("tempdir"))        // = /mnt/data/tmp
 new Path(conf.get("basedir"), "tmp") // = /user/wastl/tmp