[HADOOP-7777] Implement a base class for DNSToSwitchMapping implementations that can offer extra topology information

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.23.0, 0.24.0
• Fix Version/s: 0.23.1
• Component/s: util
• Target Version/s: 0.23.0, 0.24.0
• Assignee: Steve Loughran
• Reporter: Steve Loughran
• Created: 27/Oct/11 16:42
• Updated: 10/Mar/15 02:09
• Resolved: 28/Nov/11 21:34

Description

HDFS-2492 has identified a need for DNSToSwitchMapping implementations to provide a bit more topology information (e.g. whether or not there are multiple switches). This could be done by writing an extended interface, querying its methods if present and coming up with a default action if there is no extended interface.

Alternatively, we have a base class that all the standard mappings implement, with a boolean isMultiRack() method; all the standard subclasses would extend this, as could any third party topology provider. The advantage of this approach is that it is easier to add new operations without going into a multi-interface mess.

Issue Links

• is depended upon by: HDFS-2492 BlockManager cross-rack replication checks only work for ScriptBasedMapping
• is related to: HADOOP-7878 Regression HADOOP-7777 switch changes break HDFS tests when the isSingleSwitch() predicate is used
• is related to: HADOOP-8231 Make topologies easier to set up and debug