Print Dynatrace original_core_pattern in javacore if available

[kgibm]

A very common Linux kernel.core_pattern is |/opt/dynatrace/oneagent/agent/rdp installed by the 3rd party monitoring product Dynatrace. When rdp is installed, it saves off the previous kernel.core_pattern into /opt/dynatrace/oneagent/agent/conf/original_core_pattern. When rdp handles a core dump, it first processes it internally, and then sends the core dump to the program in original_core_pattern.

Therefore, it's very common to see the following in a javacore:

2CISYSINFO     /proc/sys/kernel/core_pattern = |/opt/dynatrace/oneagent/agent/rdp

However, that doesn't really help understand where the core dump went because the javacore doesn't print /opt/dynatrace/oneagent/agent/conf/original_core_pattern. This leads to an extra back-and-forth with a customer.

If it's acceptable for J9 to reference third party file locations, then this PR adds this if available. Example from a local build:

2CISYSINFO     /proc/sys/kernel/core_pattern = |/opt/dynatrace/oneagent/agent/rdp
2CISYSINFO     /proc/sys/kernel/core_uses_pid = 1
2CISYSINFO     /opt/dynatrace/oneagent/agent/conf/original_core_pattern = |/usr/lib/systemd/systemd-coredump %P %u %g %s %t %c %h

I also increased the amount of characters printed from such files from 80 to 255 as 80 seemed a bit low to me.

@keithc-ca @pshipton

[keithc-ca]

I don't think it's reasonable to hard-code this path. Perhaps it should instead be derived from the contents of /proc/sys/kernel/core_pattern. Suppose dynatrace is installed under /usr/local (instead of the default location) so core_pattern contains:

|/usr/local/dynatrace/oneagent/agent/rdp

In that case, the file we want to see might be /usr/local/dynatrace/oneagent/agent/conf/original_core_pattern.

These changes only apply for Linux: What about other platforms where OneAgent is supported?

[kgibm]

That makes sense, will do.

What about other platforms where OneAgent is supported?

Their Crash Analysis page only discusses Linux. Presumably, core dumps on other platforms will just be standard.

[keithc-ca]

Jenkins compile aix,alinux64,amac,win jdk17

[kgibm]

Thanks!

Note that in containers, the core dump processing program that processes a container core dump runs on the worker node rather than in the container, so the container, by default, will not have access to original_core_pattern and thus it won't be shown in a javacore taken inside a container.

For posterity, tested with:

mkdir -p /opt/dynatrace/oneagent/agent/conf/
cp /bin/true /opt/dynatrace/oneagent/agent/rdp
echo "|/usr/lib/systemd/systemd-coredump %P %u %g %s %t %c %h" > /opt/dynatrace/oneagent/agent/conf/original_core_pattern
sysctl -w kernel.core_pattern="|/opt/dynatrace/oneagent/agent/rdp"
sysctl kernel.core_pattern
OUTPUT="$(build/linux-x86_64-server-release/images/jdk/bin/java -Xdump:java:events=vmstop -version 2>&1)"
echo "${OUTPUT}"
grep -A 1 core_pattern $(echo "${OUTPUT}" | awk '/JVMDUMP010I/ { print $NF; }')