Kafka itself doesn't pull any data. It is a data persistence store. One question: Why do you need Kafka? It is a great persistence store and a great input layer for Storm/Spark Streaming because of its replay capabilities. However databases have similar characteristics. So you normally should be able to directly connect to the RDBMS with Storm/Spark as well.
But lets think how you could implement real-time streaming from a database:
1) Best way IMO: push data into Kafka at the same time you put it in the database. I.e. don't pull it OUT of the DB, push it in Kafka at the same time you put it into the DB. ( for example by adding a second hook to the web app that writes the data. ) You can then use Kafka for all analytics, use it as a source for your warehouse and realtime analytics and you do not need to do the ETL that is normally needed on the transactional db. Its also as realtime as it gets. However this is not always possible.
2) There are some log replication tools that can integrate with Kafka
http://www.oracle.com/us/products/middleware/data-integration/goldengate-for-big-data-ds-2415102.pdf
GoldenGate for Java seems to fit the bill.
Edit: The Kafka guys have an example for postgres using a log replication tool called bottled water. This is the same approach. The article also explains the problem nicely.
http://www.confluent.io/blog/bottled-water-real-time-integration-of-postgresql-and-kafka/
Also pretty realtime.
3) Use some batched service that runs every x seconds/minutes and runs a SQL command that loads data with a new timestamp/ unique id and puts it into Kafka.
This can be
- a little Java Producer with a JDBC driver
- You could use Storm:
http://storm.apache.org/documentation/storm-jdbc.html
- Spark Streaming might have one as well
Or simply a scheduled job doing the copying perhaps MapReduce
https://hadoop.apache.org/docs/r2.7.0/api/org/apache/hadoop/mapred/lib/db/DBInputFormat.html
https://github.com/kafka-dev/kafka/blob/master/contrib/hadoop-producer/src/main/java/kafka/bridge/ha...
- pretty sure flume can do it as well
EDIT: Added sqoop2 for completion sake
Sqoop has a Kafka connector. But its only available in sqoop2 not sqoop1. Unfortunately HDP doesn't currently support sqoop2. So it would have to be manually installed.
http://sqoop2.readthedocs.org/en/latest/Connectors.html#kafka-connector
Obviously the last is not really realtime and the question is if you use storm or Spark why you would need kafka in the middle. Since the db is already a persisted store that can replay loads.
Hope that helps
