Weiwei Yang created HDFS-12283:

             Summary: Ozone: DeleteKey-5: Implement SCM DeletedBlockLog
                 Key: HDFS-12283
                 URL: https://issues.apache.org/jira/browse/HDFS-12283
             Project: Hadoop HDFS
          Issue Type: Sub-task
          Components: ozone, scm
            Reporter: Weiwei Yang
            Assignee: Weiwei Yang

The DeletedBlockLog is a persisted log in SCM to keep tracking container blocks 
which are under deletion. It maintains info about under-deletion container 
blocks that notified by KSM, and the state how it is processed. We can use 
RocksDB to implement the 1st version of the log, the schema looks like

||TxID||ContainerName||Block List||ProcessedCount||
|2|c2|b2, b3|-1|

Some explanations

# TxID is an incremental long value transaction ID for ONE container and 
multiple blocks
# Container name is the name of the container
# Block list is a list of block IDs
# ProcessedCount is the number of times SCM has sent this record to datanode, 
it represents the "state" of the transaction, it is in range of \[-1, 5\], -1 
means the transaction eventually failed after some retries, 5 is the max number 
times of retries.

We need to define {{DeletedBlockLog}} as an interface and implement this with 
RocksDB {{MetadataStore}} as the first version.

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