pipeline_kafka

PipelineDB extension for Kafka support

Requirements

You'll need to have librdkafka installed on your system to build the extension. The easiest way to install it is to built it from source.

git clone -b 0.9.1 https://github.com/edenhill/librdkafka.git ~/librdkafka
cd ~/librdkafka
./configure --prefix=/usr
make
sudo make install

You also need PipelineDB installed and pg_config to be on your PATH.

Installing

First build and install the extension by running:

./configure
make
make install

pipeline_kafka internally uses shared memory to sync state between background workers, so it must be preloaded as a shared library. You can do so by adding the following line to your pipelinedb.conf file. If you're already loading some shared libraries, then simply add pipeline_kafka as a comma-separated list.

shared_preload_libraries = 'pipeline_kafka'

Now you can load the extension into a database:

=# CREATE EXTENSION pipeline_kafka;
CREATE EXTENSION

Usage

pipeline_kafka needs to know about any Kafka brokers it can connect to. Brokers can be added with kafka_add_broker:

=# SELECT pipeline_kafka.add_broker('localhost:9092');
 add_broker
------------
 success
(1 row)

Consuming Messages

Assuming the existence of a stream named topic_stream that a continuous view is reading from, you can now begin ingesting data from Kafka (note: only static streams can consume data from Kafka):

=# SELECT pipeline_kafka.consume_begin('kafka_topic', 'topic_stream');
 consume_begin
---------------
 success
(1 row)

This will launch a background worker that will read from the Kafka topic kafka_topic, and use COPY to write the messages to topic_stream. You can specifiy the format that COPY should expect, as well as a delimiter, quote and escape character:

=# SELECT pipeline_kafka.consume_begin('kafka_topic', 'topic_stream', format := 'text', delimiter := E'\t');
 consume_begin
---------------
 success
(1 row)

Additionally, a parallelism argument can be specified that will evenly assign a subset of the topic's partitions to each consumer process:

=# SELECT pipeline_kafka.consume_begin('kafka_topic', 'topic_stream', parallelism := 4);
 consume_begin
---------------
 success
(1 row)

To stop the worker, run:

=# SELECT pipeline_kafka.consume_end('kafka_topic', 'topic_stream');
 consume_end
-------------
 success
(1 row)

All existing consumers can be started or stopped at once by not passing any arguments to the previous functions:

=# SELECT pipeline_kafka.consume_begin();
 consume_begin
---------------
 success
(1 row)

=# SELECT pipeline_kafka.consume_end();
 consume_end
-------------
 success
(1 row)

Producing Messages

You can also produce messages into Kafka topics.

=# SELECT pipeline_kafka.produce_message('kafka_topic', 'hello world!');
 produce_message
-----------------
 success
(1 row

You can also specify a parition key or an explicit partition to produce the message into.

=# SELECT pipeline_kafka.produce_message('kafka_topic', 'hello world!', partition := 2);
 produce_message
-----------------
 success
(1 row

pipeline_kafka also comes with a trigger function that can be used to produced JSON serialized tuples into Kafka topics. The trigger function can be only be used by AFTER [INSERT | UPDATE] and FOR EACH ROW triggers.

=# CREATE TRIGGER tg
     AFTER UPDATE ON t FOR EACH ROW WHEN (x = 1)
     EXECUTE PROCEDURE pipeline_kafka.emit_tuple('kafka_topic');
CREATE TRIGGER

Documentation

You find the documentation for pipeline_kafka here.