Prerequisites
1)Download HDP Sandbox
2)MySQL database (Should
already be present in the sandbox) 3)Nifi 0.6 or later
( Download and install a new version of NIFI or use Ambari to install NIFI in
the sandbox) MySQL setup (Source Database) In this setup we will create
a table in MySQL tables and create a few triggers on the tables to emulate transactions.
These triggers will find out if the change introduced
was an insert or an update also will update the time stamp on the
updated/inserted row. ( This is very important as Nifi Will be polling on this
column to extract changes based on the time stamp) unix> mysql –u root –p
unix>Enter
password:<enter>
mysql>
mysql> create database
test_cdc;
mysql> create user
'test_cdc'@'localhost' identified by 'test_cdc';
mysql> GRANT ALL
PRIVILEGES ON *.* TO 'test_CDC'@'%' IDENTIFIED BY 'test_CDC' WITH GRANT OPTION;
mysql>Flush Privileges
mysql> exit;
unix> mysql –u test_cdc –p
test_cdc
mysql>create table CDC_TEST
(
Column_A int,
Column_B text,
Created_date datetime,
INFORMATION text
);
Create Triggers in MYSQL mysql> create trigger CDC_insert
before insert on
cdc_test
for each row
set
NEW.created_date =NOW()
, NEW.information = 'INSERT';
mysql> create trigger CDC_UPDATE
before update on
cdc_test
for each row
set
NEW.created_date = NOW()
, NEW.information = 'UPDATE';
HIVE setup (Destination Database) In hive, we have created an
external table, with exactly same data structure as MySQL table, NIFI would be
used to capture changes from the source and insert them into the Hive table. Using AMBARI Hive view or
from HIVE CLI create the following table in the hive default database: I have used hive cli to
create the table: Unix> hive Hive> create external table
HIVE_TEST_CDC
( COLUMN_A int ,
COLUMN_B string,
CREATED_DATE string,
INFORMATION string)
stored as avro
location '/test-nifi/CDC/' Note: I am not including how to
create Managed Hive table with ORC format, that would be covered in a different
article. Nifi Setup : This is a simple NIFI setup,
the queryDatabase table processor is only available as part of default
processors from version 0.6 of Nifi. queryDatabaseProcessor Configuration Its very intuitive The main things to configure
is DBCPConnection Pool and Maximum-value Columns Please choose this to be the
date-time stamp column that could be a cumulative change-management column This is the only limitation
with this processor as it is not a true CDC and relies on one column. If the
data is reloaded into the column with older data the data will not be
replicated into HDFS or any other destination. This processor does not rely
on Transactional logs or redo logs like Attunity or Oracle Goldengate. For a
complete solution for CDC please use Attunity or Oracle Goldengate solutions. DBCPConnectionPool Configuration: putHDFS processor configure the Hadoop
Core-site.xml and hdfs-site.xml and destination HDFS directory in this case it
is /test-nifi/CDC Make sure this directory is
present in HDFS otherwise create it using the following command Unix>
hadoop fs –mkdir –p /test-nifi/CDC Make
sure all the processors are running in NiFi
Testing CDC Run
a bunch of insert statements on MySQL database. mysql –u test_cdc –p at the mysql CLI run the following inserts: insert into cdc_test values (3, 'cdc3', null,
null); insert into cdc_test values (4, 'cdc3', null,
null); insert into cdc_test values (5, 'cdc3', null,
null); insert into cdc_test values (6, 'cdc3', null,
null); insert into cdc_test values (7, 'cdc3', null,
null); insert into cdc_test values (8, 'cdc3', null,
null); insert into cdc_test values (9, 'cdc3', null,
null); insert into cdc_test values (10, 'cdc3', null,
null); insert into cdc_test values (11, 'cdc3', null,
null); insert into cdc_test values (12, 'cdc3', null,
null); insert into cdc_test values (13, 'cdc3', null,
null); select * from cdc_test go to hive using cli and
check if the records were transferred over using NIFI. Hive> select * from
hive_test_cdc Voila…
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