I have a requirement to read messages from a topic, enrich the message based on provided configuration (data required for enrichment is sourced from external systems), and publish the enriched message to an output topic. Messages on both source and output topics should be Avro format.
Is this a good use case for a custom Kafka Connector or should I use Kafka Streams?
Why I am considering Kafka Connect?
Lightweight in terms of code and deployment
Configuration driven
Connection and error handling
Scalability
I like the plugin based approach in Connect. If there is a new type of message that needs to be handled I just deploy a new connector without having to deploy a full scale Java app.
Why I am not sure this is good candidate for Kafka Connect?
Calls to external system
Can Kafka be both source and sink for a connector?
Can we use Avro schemas in connectors?
Performance under load
Cannot do stateful processing (currently there is no requirement)
I have experience with Kafka Streams but not with Connect
Use both?
Use Kafka Connect to source external database into a topic.
Use Kafka Streams to build that topic into a stream/table that can then be manipulated.
Use Kafka Connect to sink back into a database, or other system other than Kafka, as necessary.
Kafka Streams can also be config driven, use plugins (i.e. reflection), is just as scalable, and has no different connection modes (to Kafka). Performance should be the similar. Error handling is really the only complex part. ksqlDB is entirely "config driven" via SQL statements, and can connect to external Connect clusters, or embed its own.
Avro works for both, yes.
Some connectors are temporarily stateful, as they build in-memory batches, such as S3 or JDBC sink connectors
Related
I'm currently planning the architecture for an application that reads from a Kafka topic and after some conversion puts data to RabbitMq.
I'm kind new for Kafka Streams and they look a good choice for my task. But the problem is that Kafka server is hosted at another vendor's place, so I can't even install Cafka Connector to RabbitMq Sink plugin.
Is it possible to write Kafka steam application that doesn't have any Sink points, but just processes input stream? I can just push to RabbitMQ in foreach operations, but I'm not sure will Stream even work without a sink point.
foreach is a Sink action, so to answer your question directly, no.
However, Kafka Streams should be limited to only Kafka Communication.
Kafka Connect can be installed and ran anywhere, if that is what you wanted to use... You can also use other Apache tools like Camel, Spark, NiFi, Flink, etc to write to RabbitMQ after consuming from Kafka, or write any application in a language of your choice. For example, the Spring Integration or Cloud Streams frameworks allows a single contract between many communication channels
I'm reading up on Kafka and Kafka Connect. The documentation mentions 'Kafka sources' and 'Kafka sinks' in a generic sort of way in Kafka Connect documentation. I'm not certain if these two terms are specific to Kafka Connect or they are simply referring Producers and Consumers.
If you are in need to bring data into your kafka cluster or copy data outside of your kafka ( copy data from / into kafka ) there are many tools supporting you on that task ,
You might as well write and MAINTAIN your code with Kafka Consumer / Producer API
In order to avoid struggling to create new code for "already solved problem" kafka community developed the Kafka Connect framework.
the "kafka way" is by leveraging its internal ecosystem tool named kafka connect.
kafka connect is a distributed framework which has many connectors supported by community or vendor. open sourced or proprietary, there is big and growing hub "market place" for any need.
connector is piece of pluggable code (JAR files) that runs inside the framework, there are two types of connectors , sink connector is "read from kafka and sink to target", and source connector which is "read from data source and write to kafka".
in order to set up a connector you are just setting a configuration file with all the required parameters, without the need of any programming skills. no code. losing some flexibility in favor of simplicity
Kafka Streams is good, but I have to do every configuration very manual. Instead Kafka Connect provides its API interface, which is very useful for handling the configuration, as well as Tasks, Workers, etc...
Thus, I'm thinking of using Kafka Connect for my simple data transforming service. Basically, the service will read the data from a topic and send the transformed data to another topic. In order to do that, I have to make a custom Sink Connector to send the transformed data to the kafka topic, however, it seems those interface functions aren't available in SinkConnector. If I can do it, that would be great since I can manage tasks, workers via the REST API and running the tasks under a distributed mode (multiple instances).
There are 2 options in my mind:
Figuring out how to send the message from SinkConnector to a kafka topic
Figuring out how to build a REST interface API like Kafka Connect which wraps up the Kafka Streams app
Any ideas?
Figuring out how to send the message from SinkConnector to a kafka topic
A sink connector consumes data/messages from a Kafka topic. If you want to send data to a Kafka topic you are likely talking about a source connector.
Figuring out how to build a REST interface API like Kafka Connect which wraps up the Kafka Streams app.
using the kafka-connect-archtype you can have a template to create your own Kafka connector (source or sink). In your case that you want to build some stream processing pipeline after the connector, you are mostly talking about a connector of another stream processing engine that is not Kafka-stream. There are connectors for Kafka <-> Spark, Kafka <-> Flink, ...
But you can build your using the template of kafka-connect-archtype if you want. Use the MySourceTask List<SourceRecord> poll() method or the MySinkTask put(Collection<SinkRecord> records) method to process the records as stream. They extend the org.apache.kafka.connect.[source.SourceTask|sink.SinkTask] from Kafka connect.
a REST interface API like Kafka Connect which wraps up the Kafka Streams app
This is exactly what KsqlDB allows you to do
Outside of creating streams and tables with SQL queries, it offers a REST API as well as can interact with Connect endpoints (or embed a Connect worker itself)
https://docs.ksqldb.io/en/latest/concepts/connectors/
I need to push data from database(say Oracle DB) to a kafka topic by calling a stored procedure.I need to do some validations too on message
Should i use a Producer API or Kafka Connector.
You should use Kafka Connect. Either that, or use the producer API and write some code that handles:
Scale-out
Failover
Restarts
Schemas
Serialisation
Transformations
and that integrates with hundreds of other technologies in a standardised manner for ease of portability and management.
At which point, you'll have reinvented Kafka Connect ;-)
To learn more about Kafka Connect see this talk. To learn about the specifics of database->Kafka ingestion see this talk and this blog.
I need to understand when to use Kafka connect vs. own consumer/producer written by developer. We are getting Confluent Platform. Also to achieve fault tolerant design do we have to run the consumer/producer code ( jar file) from all the brokers ?
Kafka connect is typically used to connect external sources to Kafka i.e. to produce/consume to/from external sources from/to Kafka.
Anything that you can do with connector can be done through
Producer+Consumer
Readily available Connectors only ease connecting external sources to Kafka without requiring the developer to write the low-level code.
Some points to remember..
If the source and sink are both the same Kafka cluster, Connector doesn't make sense
If you are doing changed-data-capture (CDC) from a database and push them to Kafka, you can use a Database source connector.
Resource constraints: Kafka connect is a separate process. So double check what you can trade-off between resources and ease of development.
If you are writing your own connector, it is well and good, unless someone has not already written it. If you are using third-party connectors, you need to check how well they are maintained and/or if support is available.
do we have to run the consumer/producer code ( jar file) from all the brokers ?
Don't run client code on the brokers. Let all memory and disk access be reserved for the broker process.
when to use Kafka connect vs. own consumer/produce
In my experience, these factors should be taken into consideration
You're planning on deploying and monitoring Kafka Connect anyway, and have the available resources to do so. Again, these don't run on the broker machines
You don't plan on changing the Connector code very often, because you must restart the whole connector JVM, which would be running other connectors that don't need restarted
You aren't able to integrate your own producer/consumer code into your existing applications or simply would rather have a simpler produce/consume loop
Having structured data not tied to the a particular binary format is preferred
Writing your own or using a community connector is well tested and configurable for your use cases
Connect has limited options for fault tolerance compared to the raw producer/consumer APIs, with the drawbacks of more code, depending on other libraries being used
Note: Confluent Platform is still the same Apache Kafka
Kafka Connect:
Kafka Connect is an open-source platform which basically contains two types: Sink and Source. The Kafka Connect is used to fetch/put data from/to a database to/from Kafka. The Kafka connect helps to use various other systems with Kafka. It also helps in tracking the changes (as mentioned in one of the answers Changed Data Capture (CDC) ) from DB's to Kafka. The system maintains the offset, in order to read/write data from that particular offset to Kafka or any other database.
For more details, you can refer to https://docs.confluent.io/current/connect/index.html
The Producer/Consumer:
The Producer and Consumer are just an end system, which use the Kafka to produce and consume topics to/from Kafka. They are used where we want to broadcast the data to various consumers in a consumer group. This kind of system also maintains the lag and offsets of data for the consumer groups.
No, you don't need to run any producer/consumer while running Kafka connect. In case you want to check there is no data loss you can run the consumer while running Source Connectors. In case, of Sink Connectors, the already produced data can be verified in your database, by running their particular select queries.