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This document lists the detailed steps required for setting up Replication for CDAP :replication.

Cluster Setup

CDAP replication relies on the cluster administrator setting up replication on HBase, HDFS, Hive, and Kafka. It is assumed that CDAP is only running on the master cluster. It is assumed that you have not started CDAP before any of these steps.

HBase

Install the relevant cdap-hbase-compat package package on all hbase HBase nodes in your cluster . Compat packages are:
cdap-hbase-compat-0.96

cdap-hbase-compat-0.98

in order to use the replication status coprocessors. Note that due to HBase limitations, these coprocessors cannot be used on HBase 0.96 or 0.98. Available compat packages are:

cdap-hbase-compat-1.0
cdap-hbase-compat-1.0-cdh
cdap-hbase-compat-1.0-cdh5.5.0
cdap-hbase-compat-1.1
cdap-hbase-compat-1.2-cdh5.7.0

Modify hbase-site.xml on on all hbase HBase nodes to enable hbase replicationHBase replication, and to use the CDAP replication status coprocessors:

Code Block

<property>
  <name>hbase.replication</name>
  <value>true</value>
</property>
<property>
  <name>hbase.coprocessor.regionserver.classes</name>
  <value>co.cask.cdap.data2.replication.LastReplicateTimeObserver</value>
</property>
<property>
  <name>hbase.coprocessor.wal.classes</name>
  <value>co.cask.cdap.data2.replication.LastWriteTimeObserver</value>
</property>

Modify hbase-env.sh on on all hbase nodes HBase nodes to include the hbase coprocessor HBase coprocessor in the classpath classpath:

Code Block

export HBASE_CLASSPATH="$HBASE_CLASSPATH:/opt/cdap/<hbase-compat-version>/coprocessor/*"
 
# for example, if you're on cdh5.5.x and have installed the cdap-hbase-compat-1.0-cdh5.5.0 package:
export HBASE_CLASSPATH="$HBASE_CLASSPATH:/opt/cdap/hbase-compat-1.0-cdh5.5.0/coprocessor/*"

Restart hbase master HBase master and regionservers

HDFS

Setup HDFS replication using the solution provided by your distribution. HDFS does not have true replication, but is usually achieved by scheduling regular distcp jobs.

Hive

Setup replication for the database backing your Hive Metastore. Note that this will simply replicate the Hive metadata (which tables exist, table metadata, etc.), but not the data itself. It is assumed you will not be running Hive queries on the slave until a manual failover occurs.

For example, to setup MySQL replication, follow the steps at https://dev.mysql.com/doc/refman/5.7/en/replication-howto.html, which amount to:

...

Modify my.cnf on the master to set a server-id and use bin logging

Code Block
[mysqld] log-bin=mysql-bin server-id=1

...

Restart mysql on master

...

Modify my.cnf on the slave to set a server-id

Code Block
[mysqld] server-id=2

...

Restart mysql on slave

...

Create a replication user on the master

Code Block
mysql> CREATE USER 'repl'@'%.mydomain.com' IDENTIFIED BY 'slavepass'; mysql> GRANT REPLICATION SLAVE ON . TO 'repl'@'%.mydomain.com';

Obtain the master status

...

Enable replication from master to slave:

Code Block
master hbase shell> add_peer '[slave-name]', '[slave-zookeeper-quorum]:/[slave-zk-node]' example: master hbase shell> add_peer 'hbase2', 'hbase2-master.domain.net:2181:/hbase'

Enable replication from slave to master:

Code Block
slave hbase shell> add_peer '[master-name]', '[master-zookeeper-quorum]:/[master-zk-node]' example: slave hbase shell> add_peer 'hbase1', 'hbase1-master.domain.net:2181:/hbase'

Confirm that replication is working:

Code Block

master hbase shell> create 'repltest', 'f'
slave hbase shell> create 'repltest', 'f'
master hbase shell> enable_table_replication 'repltest'
slave hbase shell> alter 'repltest', { 'NAME' => 'f', 'REPLICATION_SCOPE' => 1 }
master hbase shell> put 'repltest', 'masterrow', 'f:v1', 'v1'
slave hbase shell> put 'repltest', 'slaverow', 'f:v1', 'v1'
master hbase shell> scan 'repltest'
slave hbase shell> scan 'repltest'

HDFS

Set up HDFS replication using the solution provided by your distribution. HDFS does not have true replication, but it is usually achieved by scheduling regular distcp jobs.

Hive

Set up replication for the database backing your Hive Metastore. Note that this will simply replicate the Hive metadata (which tables exist, table metadata, etc.), but not the data itself. It is assumed you will not be running Hive queries on the slave until a manual failover occurs.

For example, to setup MySQL replication, follow the steps at https://dev.mysql.com/doc/refman/5.7/en/replication-howto.html, which amount to:

Modify my.cnf on the master to set a server-id and use bin logging:
Code Block
[mysqld] log-bin=mysql-bin binlog_format=row server-id=1
Restart mysql on the master
Modify my.cnf on the slave to set a server-id:
Code Block
[mysqld] server-id=2
Restart MySQL on the slave
Create a replication user on the master:
Code Block
mysql> CREATE USER 'repl'@'%' IDENTIFIED BY 'slavepass'; mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'%';
In a production setup, you probably want to restrict the hostname instead of using '%'. Depending on your MySQL version, you may need to use old_password:
Code Block
mysql> SET PASSWORD FOR 'repl'@'%' = OLD_PASSWORD('slavepass');

Obtain the master status:

Code Block

mysql > SHOW MASTER STATUS;
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000003 | 73       | test         | manual,mysql     |
+------------------+----------+--------------+------------------+

Set master on the slave:

Code Block

mysql> CHANGE MASTER TO
    ->     MASTER_HOST='master_host_name',
    ->     MASTER_USER='replication_user_name', // repl
    -------+
| >     MASTER_PASSWORD='replication_password', //slavepass
    ->     MASTER_LOG_FILE='recorded_log_file_name', //mysql-bin.000003 | 73       | test
    ->     MASTER_LOG_POS=recorded_log_position; // 73

Start the slave:
Code Block
mysql> start slave

Verify slave status:

Code Block
mysql> SHOW SLAVE STATUS\G ************************* 1. row ************************* \| manual,mysql \| +------------------+----------+--------------+------------------+

Set master on the slave

Code Block

mysql> CHANGE MASTER TO
    ->     MASTER_HOST='master_host_name',
    ->     MASTER_USER='replication_user_name', // repl
    ->     MASTER_PASSWORD='replication_password', //slavepass
    ->     MASTER_LOG_FILE='recorded_log_file_name', //mysql-bin.000003
    ->     MASTER_LOG_POS=recorded_log_position; // 73

Start slave
Code Block
mysql> start slave

Verify slave status

Code Block

mysql> SHOW SLAVE STATUS\G
*************************** 1. row *************************** Slave_IO_State: Waiting for master to send event
                  Master_Host: localhost
                  Master_User: root
                  Master_Port: 13000
                Connect_Retry: 60
              Master_Log_File: master-bin.000002
          Read_Master_Log_Pos: 1307
               Relay_Log_File: slave-relay-bin.000003
                SlaveRelay_IOLog_StatePos: Waiting1508
for master to send event    Relay_Master_Log_File: master-bin.000002
             MasterSlave_IO_Host: localhostRunning: Yes
            Slave_SQL_Running: Yes
          Master_User    Replicate_Do_DB:
root          Replicate_Ignore_DB:
        Master_Port: 13000  Replicate_Do_Table:
       Replicate_Ignore_Table:
      Connect_RetryReplicate_Wild_Do_Table:
60  Replicate_Wild_Ignore_Table:
            Master_Log_File: master-bin.000002       Last_Errno: 0
  Read_Master_Log_Pos: 1307                RelayLast_Log_FileError:
slave-relay-bin.000003                 RelaySkip_Log_PosCounter: 15080
          RelayExec_Master_Log_FilePos: 1307
master-bin.000002              SlaveRelay_IOLog_RunningSpace: 1858
Yes              SlaveUntil_SQL_RunningCondition: YesNone
              Replicate_Do_DB:           ReplicateUntil_IgnoreLog_DBFile:
            Replicate_Do_Table    Until_Log_Pos: 0
      Replicate_Ignore_Table:     Master_SSL_Allowed: No
        Replicate_Wild_Do_Table:   ReplicateMaster_WildSSL_IgnoreCA_TableFile:
           Master_SSL_CA_Path:
       Last_Errno: 0      Master_SSL_Cert:
             Last_ErrorMaster_SSL_Cipher:
                 Skip_Counter: 0Master_SSL_Key:
        Seconds_Behind_Master: 0
ExecMaster_SSL_MasterVerify_LogServer_PosCert: 1307No
                RelayLast_LogIO_SpaceErrno: 0
 1858               UntilLast_IO_ConditionError:
None                UntilLast_Log_File:SQL_Errno: 0
               Last_SQL_Error:
  UntilReplicate_Ignore_LogServer_PosIds:
 0            Master_SSLServer_AllowedId: No1
                  Master_SSL_CA_FileUUID: 3e11fa47-71ca-11e1-9e33-c80aa9429562
             Master_SSLInfo_CA_Path:
  File: /var/mysqld.2/data/master.info
           Master_SSL_Cert:         SQL_Delay: 0
  Master_SSL_Cipher:        SQL_Remaining_Delay: NULL
      MasterSlave_SQL_SSLRunning_KeyState: Slave has read all relay log; waiting  Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
    for the slave I/O thread to update it
           LastMaster_IORetry_ErrnoCount: 010
                  LastMaster_IO_ErrorBind:
      Last_IO_Error_Timestamp:
        Last_SQL_Error_ErrnoTimestamp: 0
               LastMaster_SQL_Error:
  Replicate_Ignore_Server_IdsSSL_Crl:
             Master_ServerSSL_IdCrlpath: 1
                  Master_UUIDRetrieved_Gtid_Set: 3e11fa47-71ca-11e1-9e33-c80aa9429562:1-5
             MasterExecuted_InfoGtid_File: /var/mysqld.2/data/master.infoSet: 3e11fa47-71ca-11e1-9e33-c80aa9429562:1-5
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULLAuto_Position: 1
         SlaveReplicate_SQLRewrite_Running_StateDB:
Slave has read all relay log; waiting for the slave I/O thread to update it
           Master_Retry_Count: 10
                  Master_Bind:
      Last_IO_Error_Timestamp:
     Last_SQL_Error_Timestamp:
               Master_SSL_Crl:
           Master_SSL_Crlpath:
           Retrieved_Gtid_Set: 3e11fa47-71ca-11e1-9e33-c80aa9429562:1-5
            Executed_Gtid_Set: 3e11fa47-71ca-11e1-9e33-c80aa9429562:1-5
                Auto_Position: 1
         Replicate_Rewrite_DB:
                 Channel_name:

Kafka

Setup replication for the Kafka brokers you are using. Kafka MirrorMaker is the most common solution.

CDAP Setup

CDAP requires that you provide an extension that will perform HBase related DDL operations on both clusters instead of just one. To create an extension, you must implement the HBaseDDLExecutor class:

...

Channel_name:

Kafka

Set up replication for the Kafka brokers you are using. Kafka MirrorMaker (see https://kafka.apache.org/documentation.html#basic_ops_mirror_maker and https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=27846330) is the most common solution.

CDAP Setup

CDAP requires that you provide an extension that will perform HBase-related DDL operations on both clusters instead of on just one. To create an extension, you must implement the HBaseDDLExecutor class:

Code Block

/**
 * Interface providing the HBase DDL operations.
 */
public interface HBaseDDLExecutor extends Closeable {
  /**
   * Initialize the {@link HBaseDDLExecutor}.
   * @param context the context for the executor
   */
  void initialize(HBaseDDLExecutorContext context);

  /**
   * Create the specified namespace if it does not exist.
   *
   * @param name the namespace to create
   * @throws IOException if a remote or network exception occurs
   */
  boolean createNamespaceIfNotExists(String name) throws IOException;

  /**
   * Delete the specified namespace if it exists.
   *
   * @param name the namespace to delete
   * @throws IOException if a remote or network exception occurs
   * @throws IllegalStateException if there are tables in the namespace
   */
  void initializedeleteNamespaceIfExists(HBaseDDLExecutorContextString contextname) throws IOException;

  /**
   * Create the specified namespacetable if it does not exist.
   *
   * @param descriptor the descriptor for the table to create
   * @param name @param splitKeys the initial split keys for the namespacetable
to create    * @throws IOException if a remote or network exception occurs
   */
  void createNamespaceIfNotExists(String name)createTableIfNotExists(TableDescriptor descriptor, @Nullable byte[][] splitKeys)
    throws IOException;

  /**
   * DeleteEnable the specified namespacetable if it existsis disabled.
   *
   * @param namenamespace the namespace of the table to deleteenable
   * @throws@param IOExceptionname ifthe aname remoteof orthe networktable exceptionto occursenable
   * @throws IllegalStateExceptionIOException if therea areremote tablesor innetwork theexception namespaceoccurs
   */
  void deleteNamespaceIfExistsenableTableIfDisabled(String namespace, String name) throws IOException;

  /**
   * CreateDisable the specified table if it doesis not existenabled.
   *
   * @param descriptornamespace the descriptornamespace forof the table to createdisable
   * @param splitKeysname the initialname splitof keysthe fortable theto tabledisable
   * @throws IOException if a remote or network exception occurs
   */

 void createTableIfNotExists(TableDescriptor descriptor, @Nullable byte[][] splitKeys) void disableTableIfEnabled(String namespace, String name) throws IOException;

  /**
   * EnableModify the specified table. The iftable itmust isbe disabled.
   *
   * @param namespace the namespace of the table to enablemodify
   * @param name the name of the table to modify
   * @param descriptor the table to enable descriptor for the table
   * @throws IOException if a remote or network exception occurs
   * @throws IOExceptionIllegalStateException if athe remotespecified ortable networkis exceptionnot occursdisabled
   */
  void enableTableIfDisabledmodifyTable(String namespace, String name, TableDescriptor descriptor) throws IOException;

  /**
   * DisableTruncate the specified table. The iftable itmust isbe enableddisabled.
   *
   * @param namespace the namespace of the table to disabletruncate
   * @param name the name of the table to disabletruncate
   * @throws IOException if a remote or network exception occurs exception occurs
   * @throws IllegalStateException if the specified table is not disabled
   */
  void disableTableIfEnabledtruncateTable(String namespace, String name) throws IOException;

  /**
   * ModifyDelete the table specifiedif it tableexists. The table must be disabled.
   *
   * @param namespace the namespace of the table to delete
   * @param name the table to modify
   * @param name the name of the table to modify
   * @param descriptor the descriptor for the table delete
   * @throws IOException if a remote or network exception occurs
   * @throws IllegalStateException if the specified table is not disabled
   */
  void deleteTableIfExists(String namespace, String name) throws IOException;
 
  /**
   * @throwsGrant IOExceptionpermissions ifon a remotetable orto networkusers exceptionor occursgroups.
   *
@throws IllegalStateException if the* specified table@param isnamespace notthe disablednamespace of the table
*/   void* modifyTable(String namespace, String@param name the name, TableDescriptorof descriptor) throws IOException;the table
   /** @param permissions A *map Truncatefrom theuser specifiedname table.to Thethe tablepermissions mustfor bethat disabled.user, given as a *string  containing
 * @param namespace* the namespace of the table to truncate    * @param name the name of the table to truncateonly the characters  * @throws IOException if a remote or network exception occurs'a' (Admin), 'c' (Create), 'r' (Read), 'w' (Write), and 'x' (Execute).
   * @throws IllegalStateExceptionIOException if theanything specifiedgoes table is not disabled
wrong
   */
  void truncateTablegrantPermissions(String namespace, String name, Map<String, String> permissions) throws IOException;

  /**
   * Delete the table if it exists. The table must be disabled.
   *
   * @param namespace the namespace of the table to delete
   * @param name the table to delete
   * @throws IOException if a remote or network exception occurs
   * @throws IllegalStateException if the specified table is not disabled
   */
  void deleteTableIfExists(String namespace, String name) throws IOException;
}

To deploy your extension:

Create an extension directory

Code Block
$ mkdir -p /opt/cdap/master/ext/hbase/repl

Copy your jar to the directory

Code Block
$ cp myextension.jar /opt/cdap/master/ext/hbase/repl/

Modify cdap-site.xml to use your implementation of HBaseDDLExecutor

Code Block
<property> <name>hbase.ddlexecutor.extension.dir</name> <value>/opt/cdap/master/ext/hbase</value> </property>

Modify cdap-site.xml with any properties required by your executor. Anything prefixed by 'cdap.hbase.spi.hbase.' will be available through the Context object passed into your executor's initialize method

Code Block

<property>
  <name>cdap.hbase.spi.hbase.zookeeper.quorum</name>
  <value>hbase-master-i18003-1000.dev.continuuity.net:2181/cdap</value>
</property>
<property>
  <name>cdap.hbase.spi.hbase.zookeeper.session.timeout</name>
  <value>60000</value>
</property>
<property>
  <name>cdap.hbase.spi.hbase.cluster.distributed</name>
  <value>true</value>
</property>
<property>
  <name>cdap.hbase.spi.hbase.bulkload.staging.dir</name>
  <value>/tmp/hbase-staging</value>
</property>
<property>
  <name>cdap.hbase.spi.hbase.replication</name>
  <value>true</value>
</property>

Before starting CDAP on the master cluster, load the HBase coprocessors required by CDAP onto the slave cluster

Code Block
$ cdap setup coprocessors

Start CDAP on the master cluster

Code Block
$ cdap master start

...

Sample implementation of the SPI is located here.

To deploy your extension, run these steps on both your master and slave clusters:

Create an extension directory:

Code Block
$ mkdir -p /opt/cdap/master/ext/hbase/repl

Copy your JAR to the directory:

Code Block
$ cp myextension.jar /opt/cdap/master/ext/hbase/repl/

Modify cdap-site.xml to use your implementation of HBaseDDLExecutor:

Code Block
<property> <name>hbase.ddlexecutor.extension.dir</name> <value>/opt/cdap/master/ext/hbase</value> </property>

Modify cdap-site.xml with any properties required by your executor. Anything prefixed by 'cdap.hbase.spi.hbase.' will be available through the Context object passed into your executor's initialize method:

Code Block

<property>
  <name>cdap.hbase.spi.hbase.zookeeper.quorum</name>
  <value>hbase-master-i18003-1000.dev.continuuity.net:2181/cdap</value>
</property>
<property>
  <name>cdap.hbase.spi.hbase.zookeeper.session.timeout</name>
  <value>60000</value>
</property>
<property>
  <name>cdap.hbase.spi.hbase.cluster.distributed</name>
  <value>true</value>
</property>
<property>
  <name>cdap.hbase.spi.hbase.bulkload.staging.dir</name>
  <value>/tmp/hbase-staging</value>
</property>
<property>
  <name>cdap.hbase.spi.hbase.replication</name>
  <value>true</value>
</property>

Before starting CDAP on the master cluster, run a command on the slave cluster to load the HBase coprocessors required by CDAP onto the slave's HDFS:
Code Block
slave$ cdap setup coprocessors
Start CDAP on the master cluster:
Code Block
master$ cdap master start

Manual Failover Procedure

Stop all CDAP programs on the master cluster
Stop CDAP on the master cluster
Copy any HDFS files that have not yet been copied using either your distro's solution or distcp

Run the replication status tool to get cluster state:

Code Block
master$ cdap run co.cask.cdap.data.tools.ReplicationStatusTool -m -o /tmp/master_state

Copy the master state onto your slave cluster:
Code Block
master$ scp /tmp/master_state <slave>:/tmp/master_state

Verify replication has copied the required data onto the slave:

Code Block
slave$ cdap run co.cask.cdap.data.tools.ReplicationStatusTool -i /tmp/master_state ... Master and Slave Checksums match. HDFS Replication is complete. HBase Replication is complete.

Run Hive's metatool to update locations for Hive tables:

Code Block

slave$ hive --service metatool -updateLocation hdfs://[slave-namenode-host]:[slave-namenode-port] hdfs://[master-namenode-host]:[master-namenode-port] -tablePropKey avro.schema.url -serdePropKey avro.schema.url

Start CDAP on the slave:
Code Block
slave$ cdap master start

Versions Compared

Old Version 7

New Version Current

Key

Cluster Setup

HBase

HDFS

Hive

HDFS

Hive

Kafka

CDAP Setup

Kafka

CDAP Setup