Introduction

If you are using Kafka Streams in containers, openjdk:8-alpine is no longer the obvious default it once was. The main issues are Java 8 age, Alpine musl compatibility concerns, and the general need for a maintained runtime image with predictable security updates.

Prefer a Maintained JDK Distribution First

The first question is whether you really need Java 8. If the application is pinned to Java 8, look for a maintained distribution such as Eclipse Temurin or Amazon Corretto. If you can move Kafka Streams and the application to a newer JDK, that is often the better long-term answer.

A common Debian- or Ubuntu-based option:

1FROM eclipse-temurin:8-jre
2WORKDIR /app
3COPY build/libs/app.jar app.jar
4CMD ["java", "-jar", "app.jar"]

A Corretto option:

1FROM amazoncorretto:8
2WORKDIR /app
3COPY build/libs/app.jar app.jar
4CMD ["java", "-jar", "app.jar"]

These images are usually larger than Alpine-based images, but they avoid some of the surprises that come from musl-based environments and older, less predictable base combinations.

Understand Why Alpine Can Be Tricky

Alpine's appeal is size, but Kafka Streams applications are not just static binaries. They depend on the JVM, native libraries, TLS behavior, DNS resolution, and production diagnostics. In practice, many teams accept a somewhat larger base image in exchange for:

• better compatibility with common JVM expectations
• easier debugging
• more familiar package ecosystem
• fewer musl-related surprises

That tradeoff is often worth it for a stateful stream-processing application where operational stability matters more than shaving a few dozen megabytes off the base image.

Use Multi-Stage Builds to Keep Images Reasonable

If image size still matters, separate build and runtime stages:

1FROM gradle:8-jdk17 AS build
2WORKDIR /src
3COPY . .
4RUN gradle clean build
5
6FROM eclipse-temurin:17-jre
7WORKDIR /app
8COPY --from=build /src/build/libs/app.jar app.jar
9CMD ["java", "-jar", "app.jar"]

That keeps the runtime image much smaller than a full build-tool image while still using a more predictable JVM base than Alpine.

Test the Runtime, Not Just the Startup

For Kafka Streams, the image choice affects more than whether the JVM launches. It can influence TLS behavior, native library loading, DNS resolution, and the operational tooling available when you need to debug a production issue. A good migration test should include:

• startup and configuration loading
• Kafka broker connectivity
• state-store behavior
• graceful shutdown and restart
• memory usage under realistic load

Common Pitfalls

The biggest mistake is optimizing for image size before checking runtime compatibility and operational support. Kafka Streams applications are long-running stateful services, so debugging and reliability matter a lot.

Another common issue is staying on Java 8 only because an old Dockerfile used it. If the application and dependencies support a newer LTS JDK, the better replacement may be "move forward" rather than "find another Java 8 Alpine image".

People also assume any JDK base image is interchangeable. In reality, distro choice can affect certificates, libc behavior, package tooling, and troubleshooting workflow.

Finally, test RocksDB-backed state stores and network behavior in the new image before switching in production. Container migration is not only about whether java -jar starts successfully.

Summary

• A maintained JDK distribution such as Eclipse Temurin or Amazon Corretto is usually a better base than old openjdk:8-alpine.
• Alpine saves image size, but it can complicate JVM compatibility and operations.
• If possible, consider moving Kafka Streams applications to a newer LTS JDK instead of staying on Java 8.
• Use multi-stage builds to keep runtime images smaller without relying on Alpine.
• Choose the base image for stability and support first, then optimize size second.