[HDFS-14847] Erasure Coding: Blocks are over-replicated while EC decommissioning

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 3.2.0, 3.0.3, 3.1.2, 3.3.0
• Fix Version/s: 3.3.0, 3.1.4, 3.2.2
• Component/s: ec
• Hadoop Flags: Reviewed
• Assignee: Hui Fei
• Reporter: Hui Fei
• Created: 13/Sep/19 08:55
• Updated: 20/Oct/19 01:20
• Resolved: 20/Oct/19 00:57

Description

Found that Some blocks are over-replicated while ec decommissioning. Messages in log as follow

INFO BlockStateChange: Block: blk_-9223372035714984112_363779142, Expected Replicas: 9, live replicas: 8, corrupt replicas: 0, decommissioned replicas: 0, decommissioning replicas: 3, maintenance replicas: 0, live entering maintenance replicas: 0, excess replicas: 0, Is Open File: false, Datanodes having this block: 10.254.41.34:50010 10.254.54.53:50010 10.254.28.53:50010 10.254.56.55:50010 10.254.32.21:50010 10.254.33.19:50010 10.254.63.17:50010 10.254.31.19:50010 10.254.35.29:50010 10.254.51.57:50010 10.254.40.58:50010 10.254.69.31:50010 10.254.47.18:50010 10.254.51.18:50010 10.254.43.57:50010 10.254.50.47:50010 10.254.42.37:50010 10.254.57.29:50010 10.254.67.40:50010 10.254.44.16:50010 10.254.59.38:50010 10.254.53.56:50010 10.254.45.11:50010 10.254.39.22:50010 10.254.30.16:50010 10.254.35.53:50010 10.254.22.30:50010 10.254.26.34:50010 10.254.17.58:50010 10.254.65.53:50010 10.254.60.39:50010 10.254.61.20:50010 10.254.64.23:50010 10.254.21.13:50010 10.254.37.35:50010 10.254.68.30:50010 10.254.62.37:50010 10.254.25.58:50010 10.254.52.54:50010 10.254.58.31:50010 10.254.49.11:50010 10.254.55.52:50010 10.254.19.19:50010 10.254.36.40:50010 10.254.18.30:50010 10.254.20.39:50010 10.254.66.52:50010 10.254.56.32:50010 10.254.24.55:50010 10.254.34.11:50010 10.254.29.58:50010 10.254.27.40:50010 10.254.46.33:50010 10.254.23.19:50010 10.254.74.12:50010 10.254.74.13:50010 10.254.41.35:50010 10.254.67.58:50010 10.254.54.11:50010 10.254.68.14:50010 10.254.27.14:50010 10.254.51.29:50010 10.254.45.21:50010 10.254.50.56:50010 10.254.47.31:50010 10.254.40.14:50010 10.254.65.21:50010 10.254.62.22:50010 10.254.57.16:50010 10.254.36.52:50010 10.254.30.13:50010 10.254.35.12:50010 10.254.69.34:50010 10.254.34.58:50010 10.254.17.50:50010 10.254.63.12:50010 10.254.28.21:50010 10.254.58.30:50010 10.254.24.57:50010 10.254.33.50:50010 10.254.44.52:50010 10.254.32.48:50010 10.254.43.39:50010 10.254.20.37:50010 10.254.56.59:50010 10.254.22.33:50010 10.254.60.34:50010 10.254.49.19:50010 10.254.52.21:50010 10.254.23.59:50010 10.254.21.16:50010 10.254.42.55:50010 10.254.29.33:50010 10.254.53.17:50010 10.254.19.14:50010 10.254.64.51:50010 10.254.46.20:50010 10.254.66.22:50010 10.254.18.38:50010 10.254.39.17:50010 10.254.37.57:50010 10.254.31.54:50010 10.254.55.33:50010 10.254.25.17:50010 10.254.61.33:50010 10.254.26.40:50010 10.254.59.23:50010 10.254.59.35:50010 10.254.66.48:50010 10.254.41.15:50010 10.254.54.31:50010 10.254.61.50:50010 10.254.62.31:50010 10.254.17.56:50010 10.254.29.18:50010 10.254.45.16:50010 10.254.63.48:50010 10.254.22.34:50010 10.254.37.51:50010 10.254.65.49:50010 10.254.58.21:50010 10.254.42.12:50010 10.254.55.17:50010 10.254.27.13:50010 10.254.57.17:50010 10.254.67.18:50010 10.254.31.31:50010 10.254.28.12:50010 10.254.36.12:50010 10.254.21.59:50010 10.254.30.30:50010 10.254.26.50:50010 10.254.40.40:50010 10.254.32.17:50010 10.254.47.55:50010 10.254.60.55:50010 10.254.49.33:50010 10.254.68.47:50010 10.254.39.21:50010 10.254.56.14:50010 10.254.33.54:50010 10.254.69.57:50010 10.254.43.50:50010 10.254.50.13:50010 10.254.25.49:50010 10.254.18.20:50010 10.254.52.23:50010 10.254.19.11:50010 10.254.20.21:50010 10.254.74.16:50010 10.254.64.55:50010 10.254.24.48:50010 10.254.46.29:50010 10.254.51.12:50010 10.254.23.56:50010 10.254.44.59:50010 10.254.53.58:50010 10.254.34.38:50010 10.254.35.37:50010 10.254.35.16:50010 10.254.36.23:50010 10.254.41.47:50010 10.254.54.12:50010 10.254.20.59:50010 , Current Datanode: 10.254.56.55:50010, Is current datanode decommissioning: true, Is current datanode entering maintenance: false

Decommisions hang for a long time.

Deep into the code and find that There is a problem in ErasureCodingWork.java
For Example, there are 2 nodes(dn0, dn1) in decommission and an ec block group with the 2 nodes. After creating an ErasureCodingWork to reconstruct, it will create 2 replication work.
If dn0 replicates in success and dn1 replicates in failure, Then it will always create replication work for dn0. The block on dn0 is over-replicated and The block on dn1 will never replicate
Here is the initial path for this.