[HDFS-15201] SnapshotCounter hits MaxSnapshotID limit

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.3.0
• Component/s: snapshots
• Assignee: Karthik Palanisamy
• Reporter: Karthik Palanisamy
• Created: 02/Mar/20 18:15
• Updated: 27/Feb/23 09:24
• Resolved: 24/Mar/20 09:52

Description

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

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);
}

 

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).

 

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

Issue Links

• is duplicated by: HDFS-14548 Cannot create snapshot when the snapshotCounter reaches MaxSnapshotID
• links to: GitHub Pull Request #1870