The Flink Mistake Playbook: 2 Years of Real-World Debugging
Naci Simsek

TL;DR

Navigating Apache Flink can be challenging, especially when dealing with Kafka connector upgrades, serialization inefficiencies, and uneven load distribution. This session highlights solutions such as proper UID management during Kafka migrations, optimizing serialization, and adjusting max parallelism for balanced load distribution. These strategies enhance the stability and performance of your Flink applications.

Opening

In the realm of data streaming with Apache Flink, even seasoned practitioners face hurdles that can derail their pipelines. One such hurdle often involves transitioning from older Kafka connectors to newer ones, leading to bloated state files and potential system failures. Naci Simsek from Ververica shares insights from two years of real-world debugging, offering solutions to common issues that can plague Flink users and impact their systems' performance and stability.

What You'll Learn (Key Takeaways)

  • Kafka Connector Migration – Avoid bloated metadata files by updating UIDs during Kafka connector upgrades, ensuring state files don't retain obsolete data.
  • Serialization Efficiency – Prevent throughput degradation by configuring Flink to avoid Kryo fallback, using POJO serialization, and annotating unknown types.
  • Load Balancing – Achieve even load distribution by adjusting max parallelism relative to job parallelism, ensuring efficient utilization of task slots and preventing bottlenecks.

Q&A Highlights

Q: For ordering needed workloads, is there anything Flink can do to address this challenge?
A: Flink can order events based on key values within the same key slot. For timestamp-based ordering, you might need rebalancing strategies and utilize data structures like sorted lists, along with windowing logic and watermarks.

Q: Can the parallelism dynamically adjust based on the workload?
A: Yes, using Flink's reactive mode or Kubernetes Operator with auto-scaling capabilities, Flink can rescale based on workload metrics, ensuring efficient resource utilization.

This session provides critical insights into optimizing Apache Flink performance by addressing common pitfalls and offering practical, actionable solutions for data streaming practitioners.

Naci Simsek
Technical Account Manager, Ververica

With over 16 years in IT and Telecom, I began as a Customer Support Engineer at Nortel Networks and advanced through roles such as Software Engineer, Engineering Team Lead, Project Manager, and Solutions Architect at Huawei. For nearly a decade, I’ve specialized in customer-facing big data solutions—working as a Platform Engineer, BI Engineer, and Data Engineer. Today, as a Technical Account Manager at Ververica, I help customers leverage Apache Flink for real‑time data streaming on both on‑premises and cloud environments.



I hold a Computer Engineering degree from Ege University, an MBA from Bahcesehir University, and certifications including PMP® and German B1.



Outside of work, I enjoy traveling with my wife and our British Shorthair, Bamboo, along with photography, exercise, yoga, and meditation.

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