[HBASE-14978] Don't allow Multi to retain too many blocks

• Type: Improvement
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 1.2.0, 1.3.0, 2.0.0
• Fix Version/s: 1.2.0, 1.3.0, 2.0.0
• Component/s: io, IPC/RPC, regionserver

Release Note

Limiting the amount of memory resident for any one request allows the server to handle concurrent requests smoothly. To this end we added the ability to limit the size of responses to a multi request. That worked well however it correctly represent the amount of memory resident. So this issue adds on a an approximation of the number of blocks held for a request.

All clients before 1.2.0 will not get this multi request chunking based upon blocks kept. All clients 1.2.0 and after will.

• Assignee: Elliott Neil Clark
• Reporter: Elliott Neil Clark
• Created: 15/Dec/15 00:29
• Updated: 02/May/17 06:38
• Resolved: 18/Dec/15 00:15

Description

Scans and Multi's have limits on the total size of cells that can be returned. However if those requests are not all pointing at the same blocks then the KeyValues can keep alive a lot more data than their size.

Take the following example:

A multi with a list of 10000 gets to a fat row. Each column being returned in in a different block. Each column is small 32 bytes or so.

So the total cell size will be 32 * 10000 = ~320kb. However if each block is 128k then total retained heap size will be almost 2gigs.

Issue Links

• relates to: HBASE-17874 Limiting of read request response size based on block size may go wrong when blocks are read from onheap or off heap bucket cache