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https://issues.apache.org/jira/browse/HBASE-8663?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13724140#comment-13724140
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Demai Ni commented on HBASE-8663:
---------------------------------
[~ctrezzo] about your first point on multiple masters. I am thinking about two
approaches, both involve leveraging existing replication_scope(and
prerequisites HBASE-8771 , which will ensure only 0 and 1 be used as
replication_scope)
A simple approach is: set replication scope to -1 if the table/columnfam is on
slave-side. In that case the shell command can be used as below:
{code}
hbase(main):001:0> list_replicated_tables
TABLE COLUMNFAMILY CLUSTER
scores course MASTER: global
t3_dn cf1 MASTER: global
usertable family MASTER: global
t1_dn cf1 SLAVE
t2_dn cf2 SLAVE
{code}
A complex/tricky approach is to change the replication_scope dramatically, and
or just invent a new attribute 'replication_peers', an array of ID. We can use
positive ID for target-cluster, and negative ID for source-cluster, for example
{code}
hbase(main):004:0> list_peers
PEER_ID CLUSTER_KEY STATE
1 Slave_A.hbase.com:2181:/hbase ENABLED
2 Slave_B.hbase.com:2181:/hbase ENABLED
3 Slave_Master_C.hbase.com:2181:/hbase ENABLED
-1 Master_A.hbase.com:2181:/hbase ENABLED
-2 Master_B.hbase.com:2181:/hbase ENABLED
-3 Slave_Master_C.hbase.com:2181:/hbase ENABLED
>describe table
't1_dn', {NAME => 'cf1', REPLICATION_PEERS => '1,2,3', ..}
't2_dn', {NAME => 'cf1', REPLICATION_PEERS => '-1,-2',..}
't3_dn', {NAME => 'cf1', REPLICATION_PEERS => '3,-3',..}
t1_dn#cf1 is replicated from this cluster, and its slave clusters are
Slave_A,Slave_B and Slave_Master_C
t2_dn#cf1 is replicated to this cluster, and its master clusters are Master_A
and Master_B
t3_dn#cf1 is setup as Master_Slave replication, with
Slave_Master_C.hbase.com(while don't have to be the same cluster)
{code}
> a HBase Shell command to list the tables replicated (from or to) current
> cluster
> --------------------------------------------------------------------------------
>
> Key: HBASE-8663
> URL: https://issues.apache.org/jira/browse/HBASE-8663
> Project: HBase
> Issue Type: New Feature
> Components: Replication, shell
> Environment: clusters setup as Master and Slave for replication of
> tables
> Reporter: Demai Ni
> Assignee: Demai Ni
> Priority: Critical
> Attachments: HBASE-8663.PATCH, HBASE-8663-trunk-v0.patch,
> HBASE-8663-v2.PATCH
>
>
> This jira is to provide a hbase shell command which can give user can
> overview of the tables/columnfamilies currently being replicated. The
> information will help system administrator for design and planning, and also
> help application programmer to know which tables/columns should be
> watchout(for example, not to modify a replicated columnfamily on the slave
> cluster)
> Currently there is no easy way to tell which table(s)/columnfamily(ies)
> replicated from or to a particular cluster.
>
> On Master Cluster, an indirect method can be used by combining two steps: 1)
> $describe 'usertable' and 2) $list_peers to map the REPLICATION_SCOPE to
> target(aka slave) cluster
>
> On slave cluster, this is no existing API/methods to list all the tables
> replicated to this cluster.
> Here is an example, and prototype for Master cluster
> {code: title=hbase shell command:list_replicated_tables |borderStyle=solid}
> hbase(main):001:0> list_replicated_tables
> TABLE COLUMNFAMILY TARGET_CLUSTER
> scores course hdtest017.svl.ibm.com:2181:/hbase
> t3_dn cf1 hdtest017.svl.ibm.com:2181:/hbase
> usertable family hdtest017.svl.ibm.com:2181:/hbase
> 3 row(s) in 0.3380 seconds
> {code}
> {code: title=method to return all columnfamilies replicated from this cluster
> |borderStyle=solid}
> /**
> * ReplicationAdmin.listRepllicated
> * @return List of the replicated columnfamilies of this cluster for
> display.
> * @throws IOException
> */
> public List<String[]> listReplicated() throws IOException {
> List<String[]> replicatedColFams = new ArrayList<String[]>();
>
> HTableDescriptor[] tables;
>
> tables= this.connection.listTables();
>
> Map<String, String> peers = listPeers();
>
> for (HTableDescriptor table:tables) {
> HColumnDescriptor[] columns = table.getColumnFamilies();
> String tableName = table.getNameAsString();
> for (HColumnDescriptor column: columns) {
> int scope = column.getScope();
>
> if (scope!=0) {
> String[] replicatedEntry = new String[3];
> replicatedEntry[0] = tableName;
> replicatedEntry[1] = column.getNameAsString();
> replicatedEntry[2] = peers.get(Integer.toString(scope));
> replicatedColFams.add(replicatedEntry);
> }
> }
> }
>
> return replicatedColFams;
> }
> {code}
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