[jira] [Created] (HDFS-15201) SnapshotCounter hits MaxSnapshotID limit

["Karthik Palanisamy (Jira)" <ji...@apache.org>]

Karthik Palanisamy created HDFS-15201:
-----------------------------------------

             Summary: SnapshotCounter hits MaxSnapshotID limit
                 Key: HDFS-15201
                 URL: https://issues.apache.org/jira/browse/HDFS-15201
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: snapshots
            Reporter: Karthik Palanisamy
            Assignee: Karthik Palanisamy


Users reported that they are unable to take take HDFS snapshots and their snapshotCounter hits MaxSnapshotID limit. MaxSnapshotID limit is 16777215.

{code}

SnapshotManager.java

private static final int SNAPSHOT_ID_BIT_WIDTH = 24;

/**
 * Returns the maximum allowable snapshot ID based on the bit width of the
 * snapshot ID.
 *
 * @return maximum allowable snapshot ID.
 */
 public int getMaxSnapshotID() {
 return ((1 << SNAPSHOT_ID_BIT_WIDTH) - 1);
}

{code}

 

I think, SNAPSHOT_ID_BIT_WIDTH is too low. May be good idea to increase SNAPSHOT_ID_BIT_WIDTH to 31? to aline with our CURRENT_STATE_ID limit (Integer.MAX_VALUE - 1).

 

{code}

/**
 * This id is used to indicate the current state (vs. snapshots)
 */
public static final int CURRENT_STATE_ID = Integer.MAX_VALUE - 1;

{code}



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