[jira] [Created] (HDFS-12918) EC Policy defaults incorrectly to enabled in protobufs

["Zach Amsden (JIRA)" <ji...@apache.org>]

Zach Amsden created HDFS-12918:
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             Summary: EC Policy defaults incorrectly to enabled in protobufs
                 Key: HDFS-12918
                 URL: https://issues.apache.org/jira/browse/HDFS-12918
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: Zach Amsden
            Priority: Critical


According to documentation and code comments, the default setting for erasure coding policy is disabled:

/** Policy is disabled. It's policy default state. */
 DISABLED(1),

However, HDFS-12258 appears to have incorrectly set the policy state in the protobuf to enabled:

{code:java}
 message ErasureCodingPolicyProto {
    ooptional string name = 1;
    optional ECSchemaProto schema = 2;
    optional uint32 cellSize = 3;
    required uint32 id = 4; // Actually a byte - only 8 bits used
 + optional ErasureCodingPolicyState state = 5 [default = ENABLED];
  }
{code}

This means the parameter can't actually be optional, it must always be included, and existing serialized data without this optional field will be incorrectly interpreted as having erasure coding enabled.

This unnecessarily breaks compatibility and will require existing HDFS installations that store metadata in protobufs to require reformatting.

It looks like a simple mistake that was overlooked in code review.



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