Please VOTE on whether to merge HBASE-18070 feature branch to master (and HBASE-18070.branch-2 to branch-2). The VOTE runs for 24 hours. The majority prevails (+ or -).
Quoting the design lead-in: Read Replicas on the hbase:meta Table currently only does primitive read of the primary’s hfiles refreshing every (configurable) N seconds. This issue is about making it so we can do the Async WAL Replication <http://hbase.apache.org/book.html#_asnyc_wal_replication> ability, currently only available for user-space Tables, against the hbase:meta system Tables too; i.e. the primary replica pushes edits to its Replicas so they run much closer to the primaries’ state. If clients could be satisfied reading from Replicas, then we could have improved hbase:meta uptimes but also, we can distribute load off of the primary and alleviate hbase:meta Table (read) hotspotting. Each PR that comprises the feature branch has been reviewed before commit. * For the design, see [2]. * For an amalgamated PR of the 5 or 6 reviewed PRs that comprise this feature, see [3]. * For a PE report that compared performance before and after, see HBASE-25127 (no regression). * A report on ITBLL runs is pending to be attached to HBASE-18070 but runs so far show no regression with the feature enabled (ITBLL runs were done against a backport of this feature to branch-2 as the ITBLL state of master is currently an unknown). Testing continues mainly looking for further improvement and to better understand this feature in operation. Documentation is included. There are some follow-ons that have been identified but these can land later. Thanks and thanks to all who contributed to this feature; the reviewers and the testers in particular. S 1. http://hbase.apache.org/book.html#_asnyc_wal_replication 2. https://docs.google.com/document/d/1jJWVc-idHhhgL4KDRpjMsQJKCl_NRaCLGiH3Wqwd3O8/edit# This patch is currently missing HBASE-25280, a bug found in testing. 3. https://github.com/apache/hbase/pull/2643
