[HBASE-2294] Enumerate ACID properties of HBase in a well defined spec

• Type: Task
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 0.90.0
• Component/s: documentation
• Hadoop Flags: Incompatible change, Reviewed
• Assignee: Todd Lipcon
• Reporter: Todd Lipcon
• Created: 05/Mar/10 23:25
• Updated: 20/Nov/15 12:42
• Resolved: 20/Apr/10 23:18

Description

It's not written down anywhere what the guarantees are for each operation in HBase with regard to the various ACID properties. I think the developers know the answers to these questions, but we need a clear spec for people building systems on top of HBase. Here are a few sample questions we should endeavor to answer:

• For a multicell put within a CF, is the update made durable atomically?
• For a put across CFs, is the update made durable atomically?
• Can a read see a row that hasn't been sync()ed to the HLog?
• What isolation do scanners have? Somewhere between snapshot isolation and no isolation?
• After a client receives a "success" for a write operation, is that operation guaranteed to be visible to all other clients?
  etc

I see this JIRA as having several points of discussion:

• Evaluation of what the current state of affairs is
• Evaluate whether we currently provide any guarantees that aren't useful to users of the system (perhaps we can drop in exchange for performance)
• Evaluate whether we are missing any guarantees that would be useful to users of the system

Issue Links

• is related to: HBASE-2283 row level atomicity
• relates to: HBASE-2248 Provide new non-copy mechanism to assure atomic reads in get and scan