Sample project to reproduce an issue the the Paketo debug JVM buildpack.

See issue on Github: paketo-buildpacks/debug#43

Make sure to have Java JDK 11 installed. I'm using AdoptOpenJDK 11.0.11.

I'm using pack and Paketo buildpacks for building OCI containers for my Spring Boot applications (version 2.4.6). To clarify I'm not using the Spring Boot Maven plugin to create an OCI image for my applications. The applications are built using Maven and Java 11 and are running in the OCI container using JRE 11. Yesterday I ran into the issue of not being able to start a remote JVM debugging session from IntelliJ to a running container.

Error running 'Remote Debug': Unable to open debugger port (:8000): java.io.IOException "handshake failed - connection prematurally closed"

1. Build the project:

./mvnw clean package

2. Build the OCI container using pack with debug enabled:

pack build application/demo --builder paketobuildpacks/builder:base --path target/demo-0.0.1-SNAPSHOT.jar --env BP_JVM_VERSION=11 --env BP_DEBUG_ENABLED=true

3. Start the container:

docker run --rm --tty --publish 8080:8080 --publish 8000:8000 --env BPL_DEBUG_ENABLED=true application/demo

From the IDEA start a remote JVM debug session:

Error:

When I downgrade the Spring Boot application to Java 8:

pom.xml:

<properties>
    <java.version>1.8</java.version>
</properties>

and build using JDK 8:

./mvnw clean package

And build the OCI container using BP_JVM_VERSION=8:

pack build application/demo --builder paketobuildpacks/builder:base --path target/demo-0.0.1-SNAPSHOT.jar --env BP_JVM_VERSION=8 --env BP_DEBUG_ENABLED=true

and start the OCI container:

docker run --rm --tty --publish 8080:8080 --publish 8000:8000 --env BPL_DEBUG_ENABLED=true application/demo

I can start the remote JVM debug session without any problem: Connected to the target VM, address: ':8000', transport: 'socket'

The workaround I use now is to use Java 11 and build without the BP_DEBUG_ENABLED=true flag

pack build application/demo --builder paketobuildpacks/builder:base --path target/demo-0.0.1-SNAPSHOT.jar --env BP_JVM_VERSION=11

and add JVM remote debug settings myself using the JAVA_TOOL_OPTIONS:

docker run --rm --tty --publish 8080:8080 --publish 8000:8000 --env JAVA_TOOL_OPTIONS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n
address=*:8000" application/demo

A more clean work around I use today is to build the OCI image using the --env BP_DEBUG_ENABLED=true flag:

pack build application/demo --builder paketobuildpacks/builder:base --path target/demo-0.0.1-SNAPSHOT.jar --env BP_JVM_VERSION=11 --env BP_DEBUG_ENABLED=true

And explicitly set the BPL_DEBUG_PORT to *:8000

docker run --rm --tty --publish 8080:8080 --publish 8000:8000 --env BPL_DEBUG_ENABLED=true --env BPL_DEBUG_PORT=*:8000 application/demo

To me, it looks like the debug buildpack is not taking the difference between Java 8 and Java 11 command line arguments into account: Java 8:

-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8000

Java 11:

-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:8000