[HBASE-13926] Close the scanner only after Call#setResponse

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.0.0
• Component/s: regionserver, Scanners
• Hadoop Flags: Reviewed
• Assignee: Anoop Sam John
• Reporter: Anoop Sam John
• Created: 17/Jun/15 14:24
• Updated: 17/Jun/22 05:25
• Resolved: 21/Jun/15 14:35

Description

This is for HBASE-12295. We will be delivering cells directly from shared cache memory. HBASE-12295 adds a ref count based prevention mechanism to avoid block eviction, when that memory area in use by scanners. We will decrement ref count at scanner close. The memory area will be in use till a cellblock is created or PB scan reply message is built. So we can delay the close of the scanner until the response is set for the scanner Call. This is done via a RpcCallback way. The callback is set on Call at scan time. Once the setResponse is done, the Call will execute the RpcCallback.
This jira also adds a facility to do some cleanup/close during the course of scan. Scan from client makes many RPCs fetching N rows each time. Only at the end the scanner close will happen. We will add a new batchClose() facility with which we can do any cleanup after every rpc call is executed and rows fetched for return.

Issue Links

• blocks: HBASE-12295 Prevent block eviction under us if reads are in progress from the BBs