Chapter 2. Kafka Bridge quickstart Use this quickstart to try out the Streams for Apache Kafka Bridge in your local development environment. You will learn how to do the following: Produce messages to topics and partitions in your Kafka cluster Create a Kafka Bridge consumer Perform basic consumer operations, such as subscribing the consumer to topics and retrieving the messages that you produced In this quickstart, HTTP requests are formatted as curl commands that you can copy and paste to your terminal. Ensure you have the prerequisites and then follow the tasks in the order provided in this chapter. In this quickstart, you will produce and consume messages in JSON format. Prerequisites for the quickstart A Kafka cluster is running on the host machine. 2.1. Downloading a Kafka Bridge archive A zipped distribution of the Streams for Apache Kafka Bridge is available for download. Procedure Download the latest version of the Streams for Apache Kafka Bridge archive from the Customer Portal . 2.2. Installing the Kafka Bridge Use the script provided with the Kafka Bridge archive to install the Kafka Bridge. The application.properties file provided with the installation archive provides default configuration settings. The following default property values configure the Kafka Bridge to listen for requests on port 8080. Default configuration properties http.host=0.0.0.0 http.port=8080 Prerequisites The Kafka Bridge installation archive is downloaded Procedure If you have not already done so, unzip the Kafka Bridge installation archive to any directory. Run the Kafka Bridge script using the configuration properties as a parameter: For example: ./bin/kafka_bridge_run.sh --config-file= <path> /application.properties Check to see that the installation was successful in the log. HTTP-Kafka Bridge started and listening on port 8080 HTTP-Kafka Bridge bootstrap servers localhost:9092 What to do Produce messages to topics and partitions . 2.3. Producing messages to topics and partitions Use the Kafka Bridge to produce messages to a Kafka topic in JSON format by using the topics endpoint. You can produce messages to topics in JSON format by using the topics endpoint. You can specify destination partitions for messages in the request body. The partitions endpoint provides an alternative method for specifying a single destination partition for all messages as a path parameter. In this procedure, messages are produced to a topic called bridge-quickstart-topic . Prerequisites The Kafka cluster has a topic with three partitions. You can use the kafka-topics.sh utility to create topics. Example topic creation with three partitions bin/kafka-topics.sh --bootstrap-server localhost:9092 --create --topic bridge-quickstart-topic --partitions 3 --replication-factor 1 Verifying the topic was created bin/kafka-topics.sh --bootstrap-server localhost:9092 --describe --topic bridge-quickstart-topic Note If you deployed Streams for Apache Kafka on OpenShift, you can create a topic using the KafkaTopic custom resource. Procedure Using the Kafka Bridge, produce three messages to the topic you created: curl -X POST \ http://localhost:8080/topics/bridge-quickstart-topic \ -H 'content-type: application/vnd.kafka.json.v2+json' \ -d '{ "records": [ { "key": "my-key", "value": "sales-lead-0001" }, { "value": "sales-lead-0002", "partition": 2 }, { "value": "sales-lead-0003" } ] }' sales-lead-0001 is sent to a partition based on the hash of the key. sales-lead-0002 is sent directly to partition 2. sales-lead-0003 is sent to a partition in the bridge-quickstart-topic topic using a round-robin method. If the request is successful, the Kafka Bridge returns an offsets array, along with a 200 code and a content-type header of application/vnd.kafka.v2+json . For each message, the offsets array describes: The partition that the message was sent to The current message offset of the partition Example response #... { "offsets":[ { "partition":0, "offset":0 }, { "partition":2, "offset":0 }, { "partition":0, "offset":1 } ] } Additional topic requests Make other curl requests to find information on topics and partitions. List topics curl -X GET \ http://localhost:8080/topics Example response [ "__strimzi_store_topic", "__strimzi-topic-operator-kstreams-topic-store-changelog", "bridge-quickstart-topic", "my-topic" ] Get topic configuration and partition details curl -X GET \ http://localhost:8080/topics/bridge-quickstart-topic Example response { "name": "bridge-quickstart-topic", "configs": { "compression.type": "producer", "leader.replication.throttled.replicas": "", "min.insync.replicas": "1", "message.downconversion.enable": "true", "segment.jitter.ms": "0", "cleanup.policy": "delete", "flush.ms": "9223372036854775807", "follower.replication.throttled.replicas": "", "segment.bytes": "1073741824", "retention.ms": "604800000", "flush.messages": "9223372036854775807", "message.format.version": "2.8-IV1", "max.compaction.lag.ms": "9223372036854775807", "file.delete.delay.ms": "60000", "max.message.bytes": "1048588", "min.compaction.lag.ms": "0", "message.timestamp.type": "CreateTime", "preallocate": "false", "index.interval.bytes": "4096", "min.cleanable.dirty.ratio": "0.5", "unclean.leader.election.enable": "false", "retention.bytes": "-1", "delete.retention.ms": "86400000", "segment.ms": "604800000", "message.timestamp.difference.max.ms": "9223372036854775807", "segment.index.bytes": "10485760" }, "partitions": [ { "partition": 0, "leader": 0, "replicas": [ { "broker": 0, "leader": true, "in_sync": true }, { "broker": 1, "leader": false, "in_sync": true }, { "broker": 2, "leader": false, "in_sync": true } ] }, { "partition": 1, "leader": 2, "replicas": [ { "broker": 2, "leader": true, "in_sync": true }, { "broker": 0, "leader": false, "in_sync": true }, { "broker": 1, "leader": false, "in_sync": true } ] }, { "partition": 2, "leader": 1, "replicas": [ { "broker": 1, "leader": true, "in_sync": true }, { "broker": 2, "leader": false, "in_sync": true }, { "broker": 0, "leader": false, "in_sync": true } ] } ] } List the partitions of a specific topic curl -X GET \ http://localhost:8080/topics/bridge-quickstart-topic/partitions Example response [ { "partition": 0, "leader": 0, "replicas": [ { "broker": 0, "leader": true, "in_sync": true }, { "broker": 1, "leader": false, "in_sync": true }, { "broker": 2, "leader": false, "in_sync": true } ] }, { "partition": 1, "leader": 2, "replicas": [ { "broker": 2, "leader": true, "in_sync": true }, { "broker": 0, "leader": false, "in_sync": true }, { "broker": 1, "leader": false, "in_sync": true } ] }, { "partition": 2, "leader": 1, "replicas": [ { "broker": 1, "leader": true, "in_sync": true }, { "broker": 2, "leader": false, "in_sync": true }, { "broker": 0, "leader": false, "in_sync": true } ] } ] List the details of a specific topic partition curl -X GET \ http://localhost:8080/topics/bridge-quickstart-topic/partitions/0 Example response { "partition": 0, "leader": 0, "replicas": [ { "broker": 0, "leader": true, "in_sync": true }, { "broker": 1, "leader": false, "in_sync": true }, { "broker": 2, "leader": false, "in_sync": true } ] } List the offsets of a specific topic partition curl -X GET \ http://localhost:8080/topics/bridge-quickstart-topic/partitions/0/offsets Example response { "beginning_offset": 0, "end_offset": 1 } What to do After producing messages to topics and partitions, create a Kafka Bridge consumer . Additional resources POST /topics/{topicname} POST /topics/{topicname}/partitions/{partitionid} 2.4. Creating a Kafka Bridge consumer Before you can perform any consumer operations in the Kafka cluster, you must first create a consumer by using the consumers endpoint. The consumer is referred to as a Kafka Bridge consumer . Procedure Create a Kafka Bridge consumer in a new consumer group named bridge-quickstart-consumer-group : curl -X POST http://localhost:8080/consumers/bridge-quickstart-consumer-group \ -H 'content-type: application/vnd.kafka.v2+json' \ -d '{ "name": "bridge-quickstart-consumer", "auto.offset.reset": "earliest", "format": "json", "enable.auto.commit": false, "fetch.min.bytes": 512, "consumer.request.timeout.ms": 30000 }' The consumer is named bridge-quickstart-consumer and the embedded data format is set as json . Some basic configuration settings are defined. The consumer will not commit offsets to the log automatically because the enable.auto.commit setting is false . You will commit the offsets manually later in this quickstart. If the request is successful, the Kafka Bridge returns the consumer ID ( instance_id ) and base URL ( base_uri ) in the response body, along with a 200 code. Example response #... { "instance_id": "bridge-quickstart-consumer", "base_uri":"http:// <bridge_id> -bridge-service:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer" } Copy the base URL ( base_uri ) to use in the other consumer operations in this quickstart. What to do Now that you have created a Kafka Bridge consumer, you can subscribe it to topics . Additional resources POST /consumers/{groupid} 2.5. Subscribing a Kafka Bridge consumer to topics After you have created a Kafka Bridge consumer, subscribe it to one or more topics by using the subscription endpoint. When subscribed, the consumer starts receiving all messages that are produced to the topic. Procedure Subscribe the consumer to the bridge-quickstart-topic topic that you created earlier, in Producing messages to topics and partitions : curl -X POST http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/subscription \ -H 'content-type: application/vnd.kafka.v2+json' \ -d '{ "topics": [ "bridge-quickstart-topic" ] }' The topics array can contain a single topic (as shown here) or multiple topics. If you want to subscribe the consumer to multiple topics that match a regular expression, you can use the topic_pattern string instead of the topics array. If the request is successful, the Kafka Bridge returns a 204 (No Content) code only. When using an Apache Kafka client, the HTTP subscribe operation adds topics to the local consumer's subscriptions. Joining a consumer group and obtaining partition assignments occur after running multiple HTTP poll operations, starting the partition rebalance and join-group process. It's important to note that the initial HTTP poll operations may not return any records. What to do After subscribing a Kafka Bridge consumer to topics, you can retrieve messages from the consumer . Additional resources POST /consumers/{groupid}/instances/{name}/subscription 2.6. Retrieving the latest messages from a Kafka Bridge consumer Retrieve the latest messages from the Kafka Bridge consumer by requesting data from the records endpoint. In production, HTTP clients can call this endpoint repeatedly (in a loop). Procedure Produce additional messages to the Kafka Bridge consumer, as described in Producing messages to topics and partitions . Submit a GET request to the records endpoint: curl -X GET http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/records \ -H 'accept: application/vnd.kafka.json.v2+json' After creating and subscribing to a Kafka Bridge consumer, a first GET request will return an empty response because the poll operation starts a rebalancing process to assign partitions. Repeat step two to retrieve messages from the Kafka Bridge consumer. The Kafka Bridge returns an array of messages - describing the topic name, key, value, partition, and offset - in the response body, along with a 200 code. Messages are retrieved from the latest offset by default. HTTP/1.1 200 OK content-type: application/vnd.kafka.json.v2+json #... [ { "topic":"bridge-quickstart-topic", "key":"my-key", "value":"sales-lead-0001", "partition":0, "offset":0 }, { "topic":"bridge-quickstart-topic", "key":null, "value":"sales-lead-0003", "partition":0, "offset":1 }, #... Note If an empty response is returned, produce more records to the consumer as described in Producing messages to topics and partitions , and then try retrieving messages again. What to do After retrieving messages from a Kafka Bridge consumer, try committing offsets to the log . Additional resources GET /consumers/{groupid}/instances/{name}/records 2.7. Commiting offsets to the log Use the offsets endpoint to manually commit offsets to the log for all messages received by the Kafka Bridge consumer. This is required because the Kafka Bridge consumer that you created earlier, in Creating a Kafka Bridge consumer , was configured with the enable.auto.commit setting as false . Procedure Commit offsets to the log for the bridge-quickstart-consumer : curl -X POST http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/offsets Because no request body is submitted, offsets are committed for all the records that have been received by the consumer. Alternatively, the request body can contain an array ( OffsetCommitSeekList ) that specifies the topics and partitions that you want to commit offsets for. If the request is successful, the Kafka Bridge returns a 204 code only. What to do After committing offsets to the log, try out the endpoints for seeking to offsets . Additional resources POST /consumers/{groupid}/instances/{name}/offsets 2.8. Seeking to offsets for a partition Use the positions endpoints to configure the Kafka Bridge consumer to retrieve messages for a partition from a specific offset, and then from the latest offset. This is referred to in Apache Kafka as a seek operation. Procedure Seek to a specific offset for partition 0 of the quickstart-bridge-topic topic: curl -X POST http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/positions \ -H 'content-type: application/vnd.kafka.v2+json' \ -d '{ "offsets": [ { "topic": "bridge-quickstart-topic", "partition": 0, "offset": 2 } ] }' If the request is successful, the Kafka Bridge returns a 204 code only. Submit a GET request to the records endpoint: curl -X GET http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/records \ -H 'accept: application/vnd.kafka.json.v2+json' The Kafka Bridge returns messages from the offset that you seeked to. Restore the default message retrieval behavior by seeking to the last offset for the same partition. This time, use the positions/end endpoint. curl -X POST http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/positions/end \ -H 'content-type: application/vnd.kafka.v2+json' \ -d '{ "partitions": [ { "topic": "bridge-quickstart-topic", "partition": 0 } ] }' If the request is successful, the Kafka Bridge returns another 204 code. Note You can also use the positions/beginning endpoint to seek to the first offset for one or more partitions. What to do In this quickstart, you have used the Streams for Apache Kafka Bridge to perform several common operations on a Kafka cluster. You can now delete the Kafka Bridge consumer that you created earlier. Additional resources POST /consumers/{groupid}/instances/{name}/positions POST /consumers/{groupid}/instances/{name}/positions/beginning POST /consumers/{groupid}/instances/{name}/positions/end 2.9. Deleting a Kafka Bridge consumer Delete the Kafka Bridge consumer that you used throughout this quickstart. Procedure Delete the Kafka Bridge consumer by sending a DELETE request to the instances endpoint. curl -X DELETE http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer If the request is successful, the Kafka Bridge returns a 204 code. Additional resources DELETE /consumers/{groupid}/instances/{name}

Commands:
http.host=0.0.0.0 http.port=8080
./bin/kafka_bridge_run.sh --config-file= <path> /application.properties
HTTP-Kafka Bridge started and listening on port 8080 HTTP-Kafka Bridge bootstrap servers localhost:9092
bin/kafka-topics.sh --bootstrap-server localhost:9092 --create --topic bridge-quickstart-topic --partitions 3 --replication-factor 1
bin/kafka-topics.sh --bootstrap-server localhost:9092 --describe --topic bridge-quickstart-topic
curl -X POST http://localhost:8080/topics/bridge-quickstart-topic -H 'content-type: application/vnd.kafka.json.v2+json' -d '{ "records": [ { "key": "my-key", "value": "sales-lead-0001" }, { "value": "sales-lead-0002", "partition": 2 }, { "value": "sales-lead-0003" } ] }'
# { "offsets":[ { "partition":0, "offset":0 }, { "partition":2, "offset":0 }, { "partition":0, "offset":1 } ] }
curl -X GET http://localhost:8080/topics
__strimzi_store_topic, __strimzi-topic-operator-kstreams-topic-store-changelog, bridge-quickstart-topic, my-topic
curl -X GET http://localhost:8080/topics/bridge-quickstart-topic
{ "name": "bridge-quickstart-topic", "configs": { "compression.type": "producer", "leader.replication.throttled.replicas": "", "min.insync.replicas": "1", "message.downconversion.enable": "true", "segment.jitter.ms": "0", "cleanup.policy": "delete", "flush.ms": "9223372036854775807", "follower.replication.throttled.replicas": "", "segment.bytes": "1073741824", "retention.ms": "604800000", "flush.messages": "9223372036854775807", "message.format.version": "2.8-IV1", "max.compaction.lag.ms": "9223372036854775807", "file.delete.delay.ms": "60000", "max.message.bytes": "1048588", "min.compaction.lag.ms": "0", "message.timestamp.type": "CreateTime", "preallocate": "false", "index.interval.bytes": "4096", "min.cleanable.dirty.ratio": "0.5", "unclean.leader.election.enable": "false", "retention.bytes": "-1", "delete.retention.ms": "86400000", "segment.ms": "604800000", "message.timestamp.difference.max.ms": "9223372036854775807", "segment.index.bytes": "10485760" }, "partitions": [ { "partition": 0, "leader": 0, "replicas": [ { "broker": 0, "leader": true, "in_sync": true }, { "broker": 1, "leader": false, "in_sync": true }, { "broker": 2, "leader": false, "in_sync": true } ] }, { "partition": 1, "leader": 2, "replicas": [ { "broker": 2, "leader": true, "in_sync": true }, { "broker": 0, "leader": false, "in_sync": true }, { "broker": 1, "leader": false, "in_sync": true } ] }, { "partition": 2, "leader": 1, "replicas": [ { "broker": 1, "leader": true, "in_sync": true }, { "broker": 2, "leader": false, "in_sync": true }, { "broker": 0, "leader": false, "in_sync": true } ] } ] }
curl -X GET http://localhost:8080/topics/bridge-quickstart-topic/partitions
[ { "partition": 0, "leader": 0, "replicas": [ { "broker": 0, "leader": true, "in_sync": true }, { "broker": 1, "leader": false, "in_sync": true }, { "broker": 2, "leader": false, "in_sync": true } ] }, { "partition": 1, "leader": 2, "replicas": [ { "broker": 2, "leader": true, "in_sync": true }, { "broker": 0, "leader": false, "in_sync": true }, { "broker": 1, "leader": false, "in_sync": true } ] }, { "partition": 2, "leader": 1, "replicas": [ { "broker": 1, "leader": true, "in_sync": true }, { "broker": 2, "leader": false, "in_sync": true }, { "broker": 0, "leader": false, "in_sync": true } ] } ]
curl -X GET http://localhost:8080/topics/bridge-quickstart-topic/partitions/0
{ "partition": 0, "leader": 0, "replicas": [ { "broker": 0, "leader": true, "in_sync": true }, { "broker": 1, "leader": false, "in_sync": true }, { "broker": 2, "leader": false, "in_sync": true } ] }
curl -X GET http://localhost:8080/topics/bridge-quickstart-topic/partitions/0/offsets
beginning_offset: 0
end_offset: 1
curl -X POST http://localhost:8080/consumers/bridge-quickstart-consumer-group -H 'content-type: application/vnd.kafka.v2+json' -d '{ "name": "bridge-quickstart-consumer", "auto.offset.reset": "earliest", "format": "json", "enable.auto.commit": false, "fetch.min.bytes": 512, "consumer.request.timeout.ms": 30000 }'
# { "instance_id": "bridge-quickstart-consumer", "base_uri":"http:// <bridge_id> -bridge-service:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer" }
curl -X POST http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/subscription -H 'content-type: application/vnd.kafka.v2+json' -d '{ "topics": [ "bridge-quickstart-topic" ] }'
curl -X GET http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/records -H 'accept: application/vnd.kafka.json.v2+json'
HTTP/1.1 200 OK content-type: application/vnd.kafka.json.v2+json # [ { "topic":"bridge-quickstart-topic", "key":"my-key", "value":"sales-lead-0001", "partition":0, "offset":0 }, { "topic":"bridge-quickstart-topic", "key":null, "value":"sales-lead-0003", "partition":0, "offset":1 }, #
curl -X POST http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/offsets
curl -X POST http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/positions -H 'content-type: application/vnd.kafka.v2+json' -d '{ "offsets": [ { "topic": "bridge-quickstart-topic", "partition": 0, "offset": 2 } ] }'
curl -X GET http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/records -H 'accept: application/vnd.kafka.json.v2+json'
curl -X POST http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer/positions/end -H 'content-type: application/vnd.kafka.v2+json' -d '{ "partitions": [ { "topic": "bridge-quickstart-topic", "partition": 0 } ] }'
curl -X DELETE http://localhost:8080/consumers/bridge-quickstart-consumer-group/instances/bridge-quickstart-consumer