[HBASE-6111] CLONE - Map tasks not local to RS

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 0.20.2, 0.90.4
• Component/s: master, regionserver

Environment

DN, TT and RS running on the same nodes, all using CDH3. Ganglia monitoring everything.

• Assignee: Unassigned
• Reporter: Tim Robertson
• Created: 27/May/12 08:00
• Updated: 13/Jun/22 16:42
• Resolved: 28/May/12 14:25

Description

I have started seeing this issue in our environment. HBASE-1672 was closed as non reproducible, so I cloned it here.

I have a 367M record table, compressed with snappy, and running a vanilla MR SCAN with no filters spawns 441 Mappers. The cluster currently has 216 slots for mappers, and the first wave all report 100% data-local mappers. As the second wave of mappers come up they don't get run locally to the RS and data locality drops.

This kills our environment, as it saturates the network at 120M which is very clear on ganglia.

I am really happy to help diagnose this, but need some guidance on what to do. I don't know enough yet about how task assignment works in MR to determine why the machines are picking up random tasks for their second effort and not one for the local RS.

Issue Links

• is a clone of: HBASE-1672 Map tasks not local to RS