[HDFS-8863] The remaining space check in BlockPlacementPolicyDefault is flawed

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 2.6.0
• Fix Version/s: 2.6.1, 2.8.0, 2.7.2, 3.0.0-alpha1
• Labels: 2.6.1-candidate
• Target Version/s: 2.7.2
• Hadoop Flags: Reviewed
• Assignee: Kihwal Lee
• Reporter: Kihwal Lee
• Created: 06/Aug/15 17:31
• Updated: 06/Jan/17 00:56
• Resolved: 20/Aug/15 14:18

Description

The block placement policy calls DatanodeDescriptor#getRemaining(StorageType}} to check whether the block is going to fit. Since the method is adding up all remaining spaces, namenode can allocate a new block on a full node. This causes pipeline construction failure and abandonBlock. If the cluster is nearly full, the client might hit this multiple times and the write can fail permanently.

Issue Links

• is related to: HDFS-8946 Improve choosing datanode storage for block placement