[HBASE-8751] Enable peer cluster to choose/change the ColumnFamilies/Tables it really want to replicate from a source cluster

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.98.1, 0.99.0
• Component/s: Replication
• Hadoop Flags: Reviewed

Release Note

From the shell's doc:
# set table / table-cf to be replicable for a peer, for a table without
# an explicit column-family list, all replicable column-families (with
# replication_scope == 1) will be replicated
 hbase> set_peer_tableCFs '2', "table1; table2:cf1,cf2; table3:cfA,cfB"

• Assignee: Honghua Feng
• Reporter: Honghua Feng
• Created: 17/Jun/13 02:01
• Updated: 21/Feb/15 23:33
• Resolved: 11/Feb/14 01:21

Description

Consider scenarios (all cf are with replication-scope=1):

1) cluster S has 3 tables, table A has cfA,cfB, table B has cfX,cfY, table C has cf1,cf2.

2) cluster X wants to replicate table A : cfA, table B : cfX and table C from cluster S.

3) cluster Y wants to replicate table B : cfY, table C : cf2 from cluster S.

Current replication implementation can't achieve this since it'll push the data of all the replicatable column-families from cluster S to all its peers, X/Y in this scenario.

This improvement provides a fine-grained replication theme which enable peer cluster to choose the column-families/tables they really want from the source cluster:

A). Set the table:cf-list for a peer when addPeer:
hbase-shell> add_peer '3', "zk:1100:/hbase", "table1; table2:cf1,cf2; table3:cf2"

B). View the table:cf-list config for a peer using show_peer_tableCFs:
hbase-shell> show_peer_tableCFs "1"

C). Change/set the table:cf-list for a peer using set_peer_tableCFs:
hbase-shell> set_peer_tableCFs '2', "table1:cfX; table2:cf1; table3:cf1,cf2"

In this theme, replication-scope=1 only means a column-family CAN be replicated to other clusters, but only the 'table:cf-list list' determines WHICH cf/table will actually be replicated to a specific peer.

To provide back-compatibility, empty 'table:cf-list list' will replicate all replicatable cf/table. (this means we don't allow a peer which replicates nothing from a source cluster, we think it's reasonable: if replicating nothing why bother adding a peer?)

This improvement addresses the exact problem raised by the first FAQ in "http://hbase.apache.org/replication.html":
"GLOBAL means replicate? Any provision to replicate only to cluster X and not to cluster Y? or is that for later?
Yes, this is for much later."

I also noticed somebody mentioned "replication-scope" as integer rather than a boolean is for such fine-grained replication purpose, but I think extending "replication-scope" can't achieve the same replication granularity flexibility as providing above per-peer replication configurations.

This improvement has been running smoothly in our production clusters (Xiaomi) for several months.