Apache Kafka
This guide shows you how to ingest a stream of records from an Apache Kafka topic into a Pinot table.
In this page, you'll learn how to import data into Pinot using Apache Kafka for real-time stream ingestion. Pinot has out-of-the-box real-time ingestion support for Kafka.
Let's set up a demo Kafka cluster locally, and create a sample topic transcript-topic
Start Kafka
Create a Kafka topic
Create schema configuration
We will publish the data in the same format as mentioned in the Stream ingestion docs. So you can use the same schema mentioned under Create Schema Configuration.
Create table configuration
The real-time table configuration for the transcript
table described in the schema from the previous step.
For Kafka, we use streamType as kafka
. See #create-table-configuration for available decoder class options. You can also write your own decoder by extending the StreamMessageDecoder
interface and putting the jar file in plugins
directory.
The lowLevel
consumer reads data per partition whereas the highLevel
consumer utilises Kafka high level consumer to read data from the whole stream. It doesn't have the control over which partition to read at a particular momemt.
For Kafka versions below 2.X, use org.apache.pinot.plugin.stream.kafka09.KafkaConsumerFactory
For Kafka version 2.X and above, use
org.apache.pinot.plugin.stream.kafka20.KafkaConsumerFactory
You can set the offset to -
smallest
to start consumer from the earliest offsetlargest
to start consumer from the latest offsettimestamp in format yyyy-MM-dd'T'HH:mm:ss.SSSZ
to start the consumer from the offset after the timestamp.datetime duration or period
to start the consumer from the offset after the period eg., '2d'.
The resulting configuration should look as follows -
Upload schema and table
Now that we have our table and schema configurations, let's upload them to the Pinot cluster. As soon as the real-time table is created, it will begin ingesting available records from the Kafka topic.
Add sample data to the Kafka topic
We will publish data in the following format to Kafka. Let us save the data in a file named as transcript.json
.
Push sample JSON into the transcript-topic
Kafka topic, using the Kafka console producer. This will add 12 records to the topic described in the transcript.json
file.
Checkin Kafka docker container
Publish messages to the target topic
Query the table
As soon as data flows into the stream, the Pinot table will consume it and it will be ready for querying. Head over to the Query Console to checkout the real-time data.
Kafka ingestion guidelines
Kafka versions in Pinot
Pinot supports 2 major generations of Kafka library - kafka-0.9 and kafka-2.x for both high and low level consumers.
Post release 0.10.0, we have started shading kafka packages inside Pinot. If you are using our latest
tagged docker images or master
build, you should replace org.apache.kafka
with shaded.org.apache.kafka
in your table config.
Upgrade from Kafka 0.9 connector to Kafka 2.x connector
Update table config for both high level and low level consumer: Update config:
stream.kafka.consumer.factory.class.name
fromorg.apache.pinot.core.realtime.impl.kafka.KafkaConsumerFactory
toorg.apache.pinot.core.realtime.impl.kafka2.KafkaConsumerFactory
.If using Stream(High) level consumer, also add config
stream.kafka.hlc.bootstrap.server
intotableIndexConfig.streamConfigs
. This config should be the URI of Kafka broker lists, e.g.localhost:9092
.
How to consume from a Kafka version > 2.0.0
This connector is also suitable for Kafka lib version higher than 2.0.0
. In Kafka 2.0 connector pom.xml, change the kafka.lib.version
from 2.0.0
to 2.1.1
will make this Connector working with Kafka 2.1.1
.
Kafka configurations in Pinot
Use Kafka partition (low) level consumer with SSL
Here is an example config which uses SSL based authentication to talk with kafka and schema-registry. Notice there are two sets of SSL options, ones starting with ssl.
are for kafka consumer and ones with stream.kafka.decoder.prop.schema.registry.
are for SchemaRegistryClient
used by KafkaConfluentSchemaRegistryAvroMessageDecoder
.
Consume transactionally-committed messages
The connector with Kafka library 2.0+ supports Kafka transactions. The transaction support is controlled by config kafka.isolation.level
in Kafka stream config, which can be read_committed
or read_uncommitted
(default). Setting it to read_committed
will ingest transactionally committed messages in Kafka stream only.
For example,
Note that the default value of this config read_uncommitted
to read all messages. Also, this config supports low-level consumer only.
Use Kafka partition (low) level consumer with SASL_SSL
Here is an example config which uses SASL_SSL based authentication to talk with kafka and schema-registry. Notice there are two sets of SSL options, some for kafka consumer and ones with stream.kafka.decoder.prop.schema.registry.
are for SchemaRegistryClient
used by KafkaConfluentSchemaRegistryAvroMessageDecoder
.
Extract record headers as Pinot table columns
Pinot's Kafka connector supports automatically extracting record headers and metadata into the Pinot table columns. The following table shows the mapping for record header/metadata to Pinot table column names:
Kafka Record | Pinot Table Column | Description |
---|---|---|
Record key: any type <K> |
| For simplicity of design, we assume that the record key is always a UTF-8 encoded String |
Record Headers: Map<String, String> | Each header key is listed as a separate column:
| For simplicity of design, we directly map the string headers from kafka record to pinot table column |
Record metadata - offset : long |
| |
Record metadata - recordTimestamp : long |
|
In order to enable the metadata extraction in a Kafka table, you can set the stream config metadata.populate
to true
.
In addition to this, if you want to use any of these columns in your table, you have to list them explicitly in your table's schema.
For example, if you want to add only the offset and key as dimension columns in your Pinot table, it can listed in the schema as follows:
Once the schema is updated, these columns are similar to any other pinot column. You can apply ingestion transforms and / or define indexes on them.
Remember to follow the schema evolution guidelines when updating schema of an existing table!
Tell Pinot where to find an Avro schema
There is a standalone utility to generate the schema from an Avro file. See [infer the pinot schema from the avro schema and JSON data](https://docs.pinot.apache.org/basics/data-import/complex-type#infer-the-pinot-schema-from-the-avro-schema-and-json-data) for details.
To avoid errors like The Avro schema must be provided
, designate the location of the schema in your streamConfigs
section. For example, if your current section contains the following:
Then add this key: "stream.kafka.decoder.prop.schema"
followed by a value that denotes the location of your schema.