Скачать или смотреть Resolving Classloader Issues in AWS Kinesis Data Analytics for Flink Applications

Learn how to manage classloader configurations and troubleshoot serialization issues in AWS Kinesis Data Analytics applications using Flink.
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Troubleshooting Classloader Configuration in AWS Kinesis Data Analytics with Flink

Developing applications that run in the cloud can sometimes lead to unexpected issues, especially when the environments are different from local setups. One common issue developers face is related to classloader configuration in applications built with Apache Flink on AWS Kinesis Data Analytics. In this guide, we'll explore a specific serialization problem and discuss its limitations within AWS's managed Flink service.

Understanding the Problem

Imagine you've developed a Flink application locally that works seamlessly. You've implemented a functionality where processed events from a Kinesis queue are written to S3 in Parquet format. However, upon deployment in AWS Kinesis Data Analytics, you encounter the following error message:

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This error typically arises from issues related to classloading — specifically, it indicates that the application is unable to find or load the necessary classes due to the way it is resolving dependencies.

The Solution You Found

To address the serialization issue, you discovered that modifying the classloader resolution strategy could potentially fix the problem. You identified that changing the property from classloader.resolve-order: child-first to classloader.resolve-order: parent-first alleviated the serialization issue when tested on a local cluster.

Classloader Resolution Strategies

Child-First: This approach first looks for classes in the child classloader (the application itself) before going to the parent classloader (the system classes). This can lead to conflicts if classes are shadowed.

Parent-First: This method prioritizes the parent classloader, allowing the application to use classes provided by the system or other libraries first, reducing the risk of conflicts.

The Limitation in AWS Kinesis Data Analytics

You might be wondering: "Can I change the classloader configuration when using AWS managed Flink?" Unfortunately, AWS Support has confirmed that the classloader.resolve-order property cannot be changed in the context of Kinesis Data Analytics applications. This limitation can be frustrating for developers who are accustomed to having control over such configurations in local or other cloud environments.

Conclusion

While AWS Kinesis Data Analytics provides a robust environment for running managed Flink applications, it does come with some restrictions. The inability to modify the classloader resolution order can pose challenges, particularly when dealing with serialization issues. As developers, we must adapt to these constraints by carefully designing our applications and thoroughly testing them both locally and in the cloud.

Key Takeaways

Be aware of the classloader settings when developing Flink applications.

Test applications in the target cloud environment to identify issues.

Understand the limitations of managed services like AWS Kinesis Data Analytics regarding configuration options.

Facing challenges with AWS Kinesis Data Analytics? You're not alone! Stay informed and adapt your strategies to ensure smoother deployments in the future.