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https://issues.apache.org/jira/browse/HBASE-8751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13768963#comment-13768963
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Feng Honghua commented on HBASE-8751:
-------------------------------------
[~jdcryans]
Thanks for the thorough code review, but below is not true:
bq. This is in ReplicationSource.removeNonReplicableEdits() and that method is
called for each HLog.Entry, which means that you'd hit ZK from all the region
servers for as many write calls as they are getting. That seems excessive.
==> zkHelper.getTableCFs(peerId) delegates to ReplicationPeer.getTableCFs, and
ReplicationPeer maintains the current table/cf configs in its tableCFs field
and returns it per getTableCFs call. And ReplicationPeer has a tableCFTracker
which is watching tableCF zk node and updates tableCFs field accordingly once
tableCF zk node is changed(by user via shell). This process is similiar to the
peer state(enable/disable) treatment.
So tableCF zk node will be access same times as it's updated, not same
times ReplicationSource.removeNonReplicableEdits() is called (for each
HLog.Entry)
> Enable peer cluster to choose/change the ColumnFamilies/Tables it really want
> to replicate from a source cluster
> ----------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-8751
> URL: https://issues.apache.org/jira/browse/HBASE-8751
> Project: HBase
> Issue Type: Improvement
> Components: Replication
> Reporter: Feng Honghua
> Attachments: HBASE-8751-0.94-V0.patch
>
>
> 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.
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