[HADOOP-8232] Provide a command line entry point to view/test topology options

• Type: Sub-task
• Status: Resolved
• Priority: Minor
• Resolution: Won't Fix
• Affects Version/s: 0.23.1
• Component/s: util
• Assignee: Unassigned
• Reporter: Steve Loughran
• Created: 30/Mar/12 16:36
• Updated: 21/Jan/21 13:35
• Resolved: 21/Jan/21 13:35

Description

Add a new command line entry point "topo" with commands for preflight checking of a clusters topology setup.

The initial operations would be to list the implementation class of the mapper, and attempt to load it, resolve a set of supplied hostnames, then dump the topology map after the resolution process.

Target audience:

1. ops teams trying to get a new/changed script working before deploying it on a cluster.
2. someone trying to write their first script.

Resolve and list the rack mappings of the given host

hadoop topo test [host1] [host2] ... 

This would load the hostnames from a given file, resolve all of them and list the results:

hadoop topo testfile filename

This version is intended for the ops team who have a list of hostnames, IP addresses.

• Rather than just list them, the ops team may want to mandate that there were no /default-rack mappings found, as that is invariably a sign that the script isn't handling a hostname properly.
• No attempt to be clever and do IP address resolution, FQDN to hostname mapping, etc.

Issue Links

• depends upon: HADOOP-8231 Make topologies easier to set up and debug
• is duplicated by: HADOOP-8049 Add entry point/script to do preflight checking of script resolution