[HDFS-5046] Hang when add/remove a datanode into/from a 2 datanode cluster

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Not A Problem
• Affects Version/s: 1.1.1
• Component/s: datanode

Environment

Red Hat Enterprise Linux Server release 5.3, 64 bit

• Assignee: Unassigned
• Reporter: sam liu
• Created: 31/Jul/13 06:36
• Updated: 31/Jul/13 16:57
• Resolved: 31/Jul/13 16:57

Description

1. Install a Hadoop 1.1.1 cluster, with 2 datanodes: dn1 and dn2. And, in hdfs-site.xml, set the 'dfs.replication' to 2
2. Add node dn3 into the cluster as a new datanode, and did not change the 'dfs.replication' value in hdfs-site.xml and keep it as 2
note: step 2 passed
3. Decommission dn3 from the cluster
Expected result: dn3 could be decommissioned successfully
Actual result:
a). decommission progress hangs and the status always be 'Waiting DataNode status: Decommissioned'. But, if I execute 'hadoop dfs -setrep -R 2 /', the decommission continues and will be completed finally.
b). However, if the initial cluster includes >= 3 datanodes, this issue won't be encountered when add/remove another datanode. For example, if I setup a cluster with 3 datanodes, and then I can successfully add the 4th datanode into it, and then also can successfully remove the 4th datanode from the cluster.