[HBASE-21154] Remove hbase:namespace table; fold it into hbase:meta

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha-1
• Component/s: meta
• Hadoop Flags: Incompatible change, Reviewed

Release Note

Add a new family called 'ns' for meta table and store the namespace related information in it instead of in namespace table. When rolling upgrading from a version which has namespace table, we will automatically migrate the data in namespace table to the 'ns' family of meta table, and then disable the namespace table. You can delete the namespace table later via the Admin interface.
The ZKNamespaceManager is also removed, as we never use its pub/sub ability in HBase.

• Assignee: Duo Zhang
• Reporter: Michael Stack
• Created: 05/Sep/18 19:41
• Updated: 22/Feb/24 07:02
• Resolved: 26/Nov/18 06:52

Description

Namespace table is a small system table. Usually it has two rows. It must be assigned before user tables but after hbase:meta goes out. Its presence complicates our startup and is a constant source of grief when for whatever reason, it is not up and available. In fact, master startup is predicated on hbase:namespace being assigned and will not make progress unless it is up.

Lets just add a new 'ns' column family to hbase:meta for namespace.

Here is a default ns table content:

hbase(main):023:0* scan 'hbase:namespace'
ROW                                                                                                      COLUMN+CELL
 default                                                                                                 column=info:d, timestamp=1526694059106, value=\x0A\x07default
 hbase                                                                                                   column=info:d, timestamp=1526694059461, value=\x0A\x05hbase

Issue Links

• breaks: HBASE-22522 The integration test in master branch's nightly job has error "ERROR: Only found 1050 rows."
• is related to: HBASE-27158 Add namespace column family to UNDELETABLE_META_COLUMNFAMILIES
• relates to: HBASE-28376 Column family ns does not exist in region during upgrade to 3.0.0-beta-2
• relates to: HBASE-21533 Add a section in our ref guide for the folding(removal) of hbase:namespace table
• relates to: HBASE-24489 Rewrite TestClusterRestartFailover.test since namespace table is gone on on master
• links to: Review Board