Amazon Kinesis Client Library for .NET

This package provides an interface to the Amazon Kinesis Client Library (KCL) MultiLangDaemon for the .NET Framework.

Developers can use the KCL to build distributed applications that process streaming data reliably at scale. The KCL takes care of many of the complex tasks associated with distributed computing, such as load balancing across multiple instances, responding to instance failures, checkpointing processed records, and reacting to changes in stream volume.

This package wraps and manages the interaction with the MultiLangDaemon, which is provided as part of the Amazon KCL for Java so that developers can focus on implementing their record processing logic.

A record processor in C# typically looks something like the following:

using Amazon.Kinesis.ClientLibrary;

namespace Sample
{
    public class RecordProcessor : IShardRecordProcessor
    {
        public void Initialize(InitializationInput input)
        {
            //
            // Initialize the record processor
            //
        }

        public void ProcessRecords(ProcessRecordsInput input)
        {
            //
            // Process a batch of records from input.Records, and optionally checkpoint by calling
            // input.Checkpointer.Checkpoint() 
            //
        }

        public void LeaseLost(LeaseLossInput leaseLossInput)
        {
            //
            // Perform any cleanup required.
            // This record processor has lost it's lease so checkpointing is not possible.
            // This is why LeaseLostInput does not provide a Checkpointer property,
            //
        }

        public void ShardEnded(ShardEndedInput shardEndedInput)
        {
            //
            // The record process has processed all records in the shard, and will no longer receive records.
            // It is required that this method call shardEndedInput.Checkpointer.Checkpoint() to inform the KCL
            // that the record processor has acknowledged the completion of the shard.
            //
        }

        public void ShutdownRequested(ShutdownRequestedInput shutdownRequestedInput)
        {
            //
            // This is called when the KCL is being shutdown, and if desired the record processor can checkpoint here
            // by calling shutdownRequestedInput.Checkpointer.Checkpoint(...)
            //
        }
    }

    internal class MainClass
    {
        public static void Main(string[] args)
        {
            KclProcess.Create(new RecordProcessor()).Run();
        }
    }
}

For more information about Amazon Kinesis and the client libraries, see the official documentation as well as the Amazon Kinesis forums.

Getting started

Set up your AWS credentials

Before running a KCL application, make sure that your environment is configured to allow the MultiLangDaemon to access your AWS security credentials.

If you've installed the AWS SDK for .NET, you may have already configured your AWS credentials using the SDK credential store in Microsoft Visual Studio; however, because Amazon KCL for .NET applications never deal with your credentials directly but defer to the MultiLangDaemon, this store is not available to your KCL application.

Instead, you can provide your credentials through environment variables (AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY) or a credential profile in your home directory.

Building and running the sample projects

In addition to source code for the Amazon KCL for .NET itself, this repository contains a sample application, which can serve as a starting point for your KCL application. To try out this sample application, you can download a ZIP of the latest sources, the contents of which can be opened as a solution in Microsoft Visual Studio.

The sample application consists of two projects:

• A data producer (SampleProducer\SampleProducer.cs)
  This program creates an Amazon Kinesis stream and continuously puts random records into it. There is commented-out code that deletes the created stream at the end; however, you should uncomment and use this code only if you do not intend to run SampleConsumer.

• A data processor (SampleConsumer\SampleConsumer.cs)
  A new instance of this program is invoked by the MultiLangDaemon for each shard in the stream. It consumes the data from the shard. If you no longer need to work with the stream after running SampleConsumer, remember to delete both the Amazon DynamoDB checkpoint table and the Kinesis stream in your AWS account.

The following defaults are used in the sample application:

• Stream name: kclnetsample
• Number of shards: 1

Running the data producer

To run the data producer, run the SampleProducer project.

Notes

• The AWS SDK for .NET must be installed as a prerequisite to running the producer.

Running the data processor

Because the Amazon KCL for .NET requires the MultiLangDaemon, which is provided by the Amazon KCL for Java, a bootstrap program has been provided. This program downloads all required dependencies prior to invoking the MultiLangDaemon, which executes the processor as a subprocess.

To run the processor, first build the SampleConsumer project, then run the bootstrap project with the following configuration:

• Working directory: the root of the SampleConsumer project
• Arguments: --properties kcl.properties --execute

Notes

• You must have Java installed.
• If you omit the --execute argument, the bootstrap program outputs a command that can be used to start the KCL directly.
• The MultiLangDaemon reads its configuration from the kcl.properties file, which contains a few important settings:
  • executableName = dotnet SampleProcessor.dll
    The name of the processor executable, make sure Bootstrap is able to find its path.
  • streamName = kclnetsample
    The name of the Kinesis stream from which to read data. This must match the stream name used by your producer.
  • More options are described in the properties file.

Cleaning up

This sample application creates a few resources in the default region of your AWS account:

• A Kinesis stream named kclnetsample, which stores the data generated by your producer
• A DynamoDB table named DotNetKinesisSample, which tracks the state of your processor

Each of these resources will continue to incur AWS service costs until they are deleted. After you are finished testing the sample application, you can delete these resources through the AWS Management Console.

What you should know about the MultiLangDaemon

The Amazon KCL for .NET uses the Amazon KCL for Java internally. We have implemented a Java-based daemon, called the MultiLangDaemon, which handles all of the heavy lifting. Our approach has the daemon spawn the user-defined record processor program as a sub-process. The MultiLangDaemon communicates with this sub-process over standard input/output using a simple protocol, and therefore the record processor program can be written in any language.

At runtime, there will always be a one-to-one correspondence between a record processor, a child process, and an Amazon Kinesis shard. The MultiLangDaemon ensures that, without any developer intervention.

In this release, we have abstracted these implementation details and exposed an interface that enables you to focus on writing record processing logic in C#. This approach enables the Amazon KCL to be language-agnostic, while providing identical features and similar parallel processing model across all languages.

Release Notes

Release 3.0.0 (January 12, 2023)

• Upgraded to use version 2.4.4 of the Amazon Kinesis Client library

Release 2.0.0 (February 27, 2019)

• Added support for Enhanced Fan-Out.
  Enhanced Fan-Out provides dedicated throughput per stream consumer, and uses an HTTP/2 push API (SubscribeToShard) to deliver records with lower latency.
• Updated the Amazon Kinesis Client Library for Java to version 2.1.2.
  • Version 2.1.2 uses 4 additional Kinesis API's
    WARNING: These additional API's may require updating any explicit IAM policies
    • RegisterStreamConsumer
    • SubscribeToShard
    • DescribeStreamConsumer
    • DescribeStreamSummary
  • For more information about Enhanced Fan-Out with the Amazon Kinesis Client Library please see the announcement and developer documentation.
• Added a new record processor interface IShardRecordProcessor. This interface closely matches the Java ShardRecordProcessor interface.
  While the original IRecordProcessor interface remains present, and will continue to work it's recommended to upgrade to the newer interface.
  • The Shutdown method from IRecordProcessor has been replaced by LeaseLost and ShardEnded.
  • Added the LeaseLost method which is invoked when a lease is lost.
    LeaseLost replaces Shutdown where ShutdownInput.Reason was ShutdownReason.ZOMBIE.
  • Added the ShardEnded method which is invoked when all records from a split or merge have been processed.
    ShardEnded replaces Shutdown where ShutdownInput.Reason was ShutdownReason.TERMINATE.
  • Added ShutdownRequested which provides the record processor a last chance to checkpoint during the Amazon Kinesis Client Library shutdown process before the lease is canceled.
    • To control how long the Amazon Kinesis Client Library waits for the record processors to complete shutdown, add timeoutInSeconds=<seconds to wait> to your properties file.
• Updated the AWS Java SDK version to 2.4.0
• MultiLangDaemon now provides logging using Logback.
  • MultiLangDaemon supports custom configurations for logging via a Logback XML configuration file.
  • The Bootstrap program was been updated to accept either -l or --log-configuration to provide a Logback XML configuration file.

See Also

• Developing Processor Applications for Amazon Kinesis Using the Amazon Kinesis Client Library
• Amazon KCL for Java
• Amazon KCL for Python
• Amazon KCL for Ruby
• Amazon KCL for Node.js
• Amazon Kinesis documentation
• Amazon Kinesis forum

License

This library is licensed under the Apache 2.0 License.