Publishing Avro Events via Kafka
Purpose:¶
This application demonstrates how to configure WSO2 Streaming Integrator Tooling to send sweet production events via Kafka transport in Avro format Using confluent Schema Registry.
Prerequisites:¶
- Set up Kafka as follows:
- Create a folder called kafka and another folder called kafka-osgi.
- Copy the following files from {KafkaHome}/libs to the kafka folder you just created:
- kafka_2.11_2.2.0.jar
- kafka_clients_2.2.0.jar
- metrics-core-2.2.0.jar
- scala_library_2.11.12.jar
- zkclient_0.11.jar
- zookeeper_3.4.13.jar
- Copy these same files to the {WSO2SIHome}/samples/sample-clients/lib folder.
- Navigate to {WSO2SIHome}/bin and issue the following command:
- For Linux: ./jartobundle.sh
- For Windows: ./jartobundle.bat
If converted successfully, the following messages are shown on the terminal for each lib file: - INFO: Created the OSGi bundle
.jar for JAR file /kafka/ .jar
- For Linux: ./jartobundle.sh
- Copy the OSGi-converted kafka libs from the kafka-osgi folder to {WSO2SIHome}/lib.
- Download confluent-5.2.1 from https://www.confluent.io/download/ and unzip.
- Save this sample.
- If there is no syntax error, the following message is shown on the console: * -Siddhi App PublishKafkaInAvroFormatUsingSchemaRegistry successfully deployed.
Executing the Sample:¶
- Navigate to {KafkaHome} and start the zookeeper node using, bin/zookeeper-server-start.sh config/zookeeper.properties
- Navigate to {KafkaHome} and start the kafka server node using, bin/kafka-server-start.sh config/server.properties
- Navigate to {ConfluentHome} and start the schema registry node using, bin/schema-registry-start ./etc/schema-registry/schema-registry.properties
- Post the avro schema to schema registry using, curl -X POST -H "Content-Type: application/json" --data '{ "schema": "{ \"type\": \"record\", \"name\": \"sweetProduction\",\"namespace\": \"sweetProduction\", \"fields\":[{ \"name\": \"name\", \"type\": \"string\" },{ \"name\": \"amount\", \"type\": \"double\" }]}"}' http://localhost:8081/subjects/sweet-production/versions
- Navigate to {WSO2SIHome}/samples/sample-clients/kafka-avro-consumer and run the 'ant' command without arguments.
- Start the Siddhi application by clicking on 'Run'.
- If the Siddhi application starts successfully, the following messages are shown on the console: - PublishKafkaInAvroFormatUsingSchemaRegistry.siddhi - Started Successfully! - Kafka version : 2.2.0 - Kafka commitId : 05fcfde8f69b0349 - Kafka producer created.
Testing the Sample:¶
Send events through one or more of the following methods.
Option 1 - Send events to the kafka sink via the event simulator: 1. Open the event simulator by clicking on the second icon or pressing Ctrl+Shift+I. 2. In the Single Simulation tab of the panel, specify the values as follows: * Siddhi App Name : PublishKafkaInAvroFormatUsingSchemaRegistry * Stream Name : SweetProductionStream 3. In the name and amount fields, enter the following values and then click Send to send the event. * name: chocolate cake * amount: 50.50 4. Send some more events.
Option 2 - Publish events with Curl to the simulator HTTP endpoint: 1. Open a new terminal and issue the following command: * curl -X POST -d '{"streamName": "SweetProductionStream", "siddhiAppName": "PublishKafkaInAvroFormatUsingSchemaRegistry","data": ["chocolate cake", 50.50]}' http://localhost:9390/simulation/single -H 'content-type: text/plain' 2. If there is no error, the following messages are shown on the terminal: * {"status":"OK","message":"Single Event simulation started successfully"}
Option 3 - Publish events with Postman to the simulator HTTP endpoint: 1. Install the 'Postman' application from the Chrome web store. 2. Launch the Postman application. 3. Make a 'Post' request to the 'http://localhost:9390/simulation/single' endpoint. Set the Content-Type to 'text/plain' and set the request body in text as follows: {"streamName": "SweetProductionStream", "siddhiAppName": "PublishKafkaInAvroFormatUsingSchemaRegistry","data": ['chocolate cake', 50.50]} 4. Click 'send'. If there is no error, the following messages are shown on the console: * "status": "OK", * "message": "Single Event simulation started successfully"
Viewing the Results:¶
See the output on the terminal of {WSO2SIHome}/samples/sample-clients/kafka-avro-consumer:
[java] [org.wso2.extension.siddhi.io.kafka.source.KafkaConsumerThread] : Event received in Kafka Event Adaptor with offSet: 2, key: null, topic: kafka_result_topic, partition: 0
[java] [io.siddhi.core.stream.output.sink.LogSink] : KafkaSample : logStream : Event{timestamp=1546973831995, data=[chocolate cake, 50.5], isExpired=false}
Notes:¶
If the message "'Kafka' sink at 'LowProductionAlertStream' has successfully connected to http://localhost:9092" does not appear, it could be that port 9092 defined in the Siddhi application is already being used by a different program. To resolve this issue, do the following, 1. Stop this Siddhi application (Click 'Run' on menu bar -> 'Stop'). 2. In this Siddhi application's source configuration, change port 9092 to an unused port. 3. Start the application and check whether the specified messages appear on the console.
@App:name("PublishKafkaInAvroFormatUsingSchemaRegistry")
@App:description('Send events via Kafka transport using Avro format')
define stream SweetProductionStream (name string, amount double);
@sink(type='kafka',
topic='kafka_result_topic',
bootstrap.servers='localhost:9092',
is.binary.message='true',
@map(type='avro',schema.registry='http://localhost:8081',schema.id='1'))
define stream LowProductionAlertStream (name string, amount double);
@info(name='EventsPassthroughQuery')
from SweetProductionStream
select *
insert into LowProductionAlertStream;
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