Developing a Kinesis Client Library Consumer in Java
The following code shows an example implementation in Java of
ProcessorFactory and RecordProcessor. If you want to take
advantage of the enhanced fan-out feature, see Using Consumers with Enhanced Fan-Out .
/* * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * Licensed under the Amazon Software License (the "License"). * You may not use this file except in compliance with the License. * A copy of the License is located at * * http://aws.amazon.com/asl/ * * or in the "license" file accompanying this file. This file is distributed * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either * express or implied. See the License for the specific language governing * permissions and limitations under the License. */ /* * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * Licensed under the Apache License, Version 2.0 (the "License"). * You may not use this file except in compliance with the License. * A copy of the License is located at * * http://www.apache.org/licenses/LICENSE-2.0 * * or in the "license" file accompanying this file. This file is distributed * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either * express or implied. See the License for the specific language governing * permissions and limitations under the License. */ import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.UUID; import java.util.concurrent.ExecutionException; import java.util.concurrent.Executors; import java.util.concurrent.Future; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.ScheduledFuture; import java.util.concurrent.TimeUnit; import java.util.concurrent.TimeoutException; import org.apache.commons.lang3.ObjectUtils; import org.apache.commons.lang3.RandomStringUtils; import org.apache.commons.lang3.RandomUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.slf4j.MDC; import software.amazon.awssdk.core.SdkBytes; import software.amazon.awssdk.regions.Region; import software.amazon.awssdk.services.cloudwatch.CloudWatchAsyncClient; import software.amazon.awssdk.services.dynamodb.DynamoDbAsyncClient; import software.amazon.awssdk.services.kinesis.KinesisAsyncClient; import software.amazon.awssdk.services.kinesis.model.PutRecordRequest; import software.amazon.kinesis.common.ConfigsBuilder; import software.amazon.kinesis.common.KinesisClientUtil; import software.amazon.kinesis.coordinator.Scheduler; import software.amazon.kinesis.exceptions.InvalidStateException; import software.amazon.kinesis.exceptions.ShutdownException; import software.amazon.kinesis.lifecycle.events.InitializationInput; import software.amazon.kinesis.lifecycle.events.LeaseLostInput; import software.amazon.kinesis.lifecycle.events.ProcessRecordsInput; import software.amazon.kinesis.lifecycle.events.ShardEndedInput; import software.amazon.kinesis.lifecycle.events.ShutdownRequestedInput; import software.amazon.kinesis.processor.ShardRecordProcessor; import software.amazon.kinesis.processor.ShardRecordProcessorFactory; import software.amazon.kinesis.retrieval.polling.PollingConfig; /** * This class will run a simple app that uses the KCL to read data and uses the AWS SDK to publish data. * Before running this program you must first create a Kinesis stream through the AWS console or AWS SDK. */ public class SampleSingle { private static final Logger log = LoggerFactory.getLogger(SampleSingle.class); /** * Invoke the main method with 2 args: the stream name and (optionally) the region. * Verifies valid inputs and then starts running the app. */ public static void main(String... args) { if (args.length < 1) { log.error("At a minimum, the stream name is required as the first argument. The Region may be specified as the second argument."); System.exit(1); } String streamName = args[0]; String region = null; if (args.length > 1) { region = args[1]; } new SampleSingle(streamName, region).run(); } private final String streamName; private final Region region; private final KinesisAsyncClient kinesisClient; /** * Constructor sets streamName and region. It also creates a KinesisClient object to send data to Kinesis. * This KinesisClient is used to send dummy data so that the consumer has something to read; it is also used * indirectly by the KCL to handle the consumption of the data. */ private SampleSingle(String streamName, String region) { this.streamName = streamName; this.region = Region.of(ObjectUtils.firstNonNull(region, "us-east-2")); this.kinesisClient = KinesisClientUtil.createKinesisAsyncClient(KinesisAsyncClient.builder().region(this.region)); } private void run() { /** * Sends dummy data to Kinesis. Not relevant to consuming the data with the KCL */ ScheduledExecutorService producerExecutor = Executors.newSingleThreadScheduledExecutor(); ScheduledFuture<?> producerFuture = producerExecutor.scheduleAtFixedRate(this::publishRecord, 10, 1, TimeUnit.SECONDS); /** * Sets up configuration for the KCL, including DynamoDB and CloudWatch dependencies. The final argument, a * ShardRecordProcessorFactory, is where the logic for record processing lives, and is located in a private * class below. */ DynamoDbAsyncClient dynamoClient = DynamoDbAsyncClient.builder().region(region).build(); CloudWatchAsyncClient cloudWatchClient = CloudWatchAsyncClient.builder().region(region).build(); ConfigsBuilder configsBuilder = new ConfigsBuilder(streamName, streamName, kinesisClient, dynamoClient, cloudWatchClient, UUID.randomUUID().toString(), new SampleRecordProcessorFactory()); /** * The Scheduler (also called Worker in earlier versions of the KCL) is the entry point to the KCL. This * instance is configured with defaults provided by the ConfigsBuilder. */ Scheduler scheduler = new Scheduler( configsBuilder.checkpointConfig(), configsBuilder.coordinatorConfig(), configsBuilder.leaseManagementConfig(), configsBuilder.lifecycleConfig(), configsBuilder.metricsConfig(), configsBuilder.processorConfig(), configsBuilder.retrievalConfig().retrievalSpecificConfig(new PollingConfig(streamName, kinesisClient)) ); /** * Kickoff the Scheduler. Record processing of the stream of dummy data will continue indefinitely * until an exit is triggered. */ Thread schedulerThread = new Thread(scheduler); schedulerThread.setDaemon(true); schedulerThread.start(); /** * Allows termination of app by pressing Enter. */ System.out.println("Press enter to shutdown"); BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); try { reader.readLine(); } catch (IOException ioex) { log.error("Caught exception while waiting for confirm. Shutting down.", ioex); } /** * Stops sending dummy data. */ log.info("Cancelling producer and shutting down executor."); producerFuture.cancel(true); producerExecutor.shutdownNow(); /** * Stops consuming data. Finishes processing the current batch of data already received from Kinesis * before shutting down. */ Future<Boolean> gracefulShutdownFuture = scheduler.startGracefulShutdown(); log.info("Waiting up to 20 seconds for shutdown to complete."); try { gracefulShutdownFuture.get(20, TimeUnit.SECONDS); } catch (InterruptedException e) { log.info("Interrupted while waiting for graceful shutdown. Continuing."); } catch (ExecutionException e) { log.error("Exception while executing graceful shutdown.", e); } catch (TimeoutException e) { log.error("Timeout while waiting for shutdown. Scheduler may not have exited."); } log.info("Completed, shutting down now."); } /** * Sends a single record of dummy data to Kinesis. */ private void publishRecord() { PutRecordRequest request = PutRecordRequest.builder() .partitionKey(RandomStringUtils.randomAlphabetic(5, 20)) .streamName(streamName) .data(SdkBytes.fromByteArray(RandomUtils.nextBytes(10))) .build(); try { kinesisClient.putRecord(request).get(); } catch (InterruptedException e) { log.info("Interrupted, assuming shutdown."); } catch (ExecutionException e) { log.error("Exception while sending data to Kinesis. Will try again next cycle.", e); } } private static class SampleRecordProcessorFactory implements ShardRecordProcessorFactory { public ShardRecordProcessor shardRecordProcessor() { return new SampleRecordProcessor(); } } /** * The implementation of the ShardRecordProcessor interface is where the heart of the record processing logic lives. * In this example all we do to 'process' is log info about the records. */ private static class SampleRecordProcessor implements ShardRecordProcessor { private static final String SHARD_ID_MDC_KEY = "ShardId"; private static final Logger log = LoggerFactory.getLogger(SampleRecordProcessor.class); private String shardId; /** * Invoked by the KCL before data records are delivered to the ShardRecordProcessor instance (via * processRecords). In this example we do nothing except some logging. * * @param initializationInput Provides information related to initialization. */ public void initialize(InitializationInput initializationInput) { shardId = initializationInput.shardId(); MDC.put(SHARD_ID_MDC_KEY, shardId); try { log.info("Initializing @ Sequence: {}", initializationInput.extendedSequenceNumber()); } finally { MDC.remove(SHARD_ID_MDC_KEY); } } /** * Handles record processing logic. The Amazon Kinesis Client Library will invoke this method to deliver * data records to the application. In this example we simply log our records. * * @param processRecordsInput Provides the records to be processed as well as information and capabilities * related to them (e.g. checkpointing). */ public void processRecords(ProcessRecordsInput processRecordsInput) { MDC.put(SHARD_ID_MDC_KEY, shardId); try { log.info("Processing {} record(s)", processRecordsInput.records().size()); processRecordsInput.records().forEach(r -> log.info("Processing record pk: {} -- Seq: {}", r.partitionKey(), r.sequenceNumber())); } catch (Throwable t) { log.error("Caught throwable while processing records. Aborting."); Runtime.getRuntime().halt(1); } finally { MDC.remove(SHARD_ID_MDC_KEY); } } /** Called when the lease tied to this record processor has been lost. Once the lease has been lost, * the record processor can no longer checkpoint. * * @param leaseLostInput Provides access to functions and data related to the loss of the lease. */ public void leaseLost(LeaseLostInput leaseLostInput) { MDC.put(SHARD_ID_MDC_KEY, shardId); try { log.info("Lost lease, so terminating."); } finally { MDC.remove(SHARD_ID_MDC_KEY); } } /** * Called when all data on this shard has been processed. Checkpointing must occur in the method for record * processing to be considered complete; an exception will be thrown otherwise. * * @param shardEndedInput Provides access to a checkpointer method for completing processing of the shard. */ public void shardEnded(ShardEndedInput shardEndedInput) { MDC.put(SHARD_ID_MDC_KEY, shardId); try { log.info("Reached shard end checkpointing."); shardEndedInput.checkpointer().checkpoint(); } catch (ShutdownException | InvalidStateException e) { log.error("Exception while checkpointing at shard end. Giving up.", e); } finally { MDC.remove(SHARD_ID_MDC_KEY); } } /** * Invoked when Scheduler has been requested to shut down (i.e. we decide to stop running the app by pressing * Enter). Checkpoints and logs the data a final time. * * @param shutdownRequestedInput Provides access to a checkpointer, allowing a record processor to checkpoint * before the shutdown is completed. */ public void shutdownRequested(ShutdownRequestedInput shutdownRequestedInput) { MDC.put(SHARD_ID_MDC_KEY, shardId); try { log.info("Scheduler is shutting down, checkpointing."); shutdownRequestedInput.checkpointer().checkpoint(); } catch (ShutdownException | InvalidStateException e) { log.error("Exception while checkpointing at requested shutdown. Giving up.", e); } finally { MDC.remove(SHARD_ID_MDC_KEY); } } } }
