Obtaining Heap Dumps when Java Process pid is 1 fails.

When trying to create a heap dump when the Java Process ID is 1 for OpenJDK8 fails with the following error

1: Unable to get pid of LinuxThreads manager thread

See Related issues

1. https://github.com/docker-library/openjdk/issues/372
2. https://github.com/docker-library/openjdk/issues/76

We have a patch that fixes this issue in Corretto-8.

Reproducer

Run

cat <<EOF > Main.java
public class Main {
        public static void main(String[] args) {
                while(true) {
                }
        }
}
EOF

cat <<EOF > Dockerfile
FROM alpine:latest

RUN apk add openjdk8

ADD Main.java ./
RUN /usr/lib/jvm/java-8-openjdk/bin/javac Main.java

ENTRYPOINT java Main
EOF

docker build . -t test-image
docker run test-image

In a separate terminal in run

docker ps # Obtain the container id for the previously executed container
docker exec -it <container_id> /bin/sh

jmap -dump:format=b,file=heap.bin 1