Raphael Abreu aelkz

Troubleshooting Production JVMs with `jcmd`

jcmd is a powerful new tool introduced in Java 7. Along with jstack and jps, it should be in your go-to tool for solving production problems on the JVM. (Come to think of it, with this tool you don't really need jps anymore)

Here's an example session with jcmd:

$ ssh wopr.qa.corp.local
$ jcmd -l
34739 sun.tools.jcmd.JCmd -l

REMOTE DEBUGGING USING INTELLIJ IDEA

1. Start your application server:

`./standalone.sh --debug``

You'll see something like the following output:

  JAVA_OPTS:  -server -verbose:gc -Xloggc:"/usr/local/devtools/rh-sso-7.2/standalone/log/gc.log" -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=3M -XX:-TraceClassUnloading -Xms1303m -Xmx1303m -XX:MetaspaceSize=96M -XX:MaxMetaspaceSize=256m -Djava.net.preferIPv4Stack=true -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true -agentlib:jdwp=transport=dt_socket,address=8787,server=y,suspend=n

This tutorial is based on the following:
https://medium.com/upinatoms-com/sharing-a-network-between-your-vmware-fusion-linux-guest-and-your-mac-os-x-host-70d98271f142

How to setup your VMWare Fusion images to use static IP addresses on Mac OS X

Working w/ CentOS 7 and RHEL 7 linux images.

Therefore this configuration don't require any changes inside linux guest VM as it network interfaces will continue using BOOTPROTO=dhcp

1. Check your current configuration for "host-only" networking:

sudo vim /Library/Preferences/VMware\ Fusion/vmnet1/dhcpd.conf

TERMUX

ifconfig.co
ifconfig.me

ifconfig | grep "inet " | grep -Fv 127.0.0.1 | awk '{print $2}'

Inside termux

apt update && apt upgrade

Install dnsmasq

Via brew or other method

Set up DNS resolver order

In order to work on every connection and on any TLD, dnsmasq needs to be the first DNS resolver receving the query.

And since dnsmasq is a local process, all DNS queries need to go to 127.0.0.1

On macOS, /etc/resolv.conf is automaticaly created, depending on a variety of things (network settings, etc), so it cannot be edited.

	#!/bin/sh
	#
	# This script parses a heap dump.
	#
	# Usage: ParseHeapDump.sh <path/to/dump.hprof> [report]*
	#
	# The leak report has the id org.eclipse.mat.api:suspects
	# The top component report has the id org.eclipse.mat.api:top_components
	#

	import sys
	import time
	import logging
	import random
	from jaeger_client import Config
	from opentracing_instrumentation.request_context import get_current_span, span_in_context

	def init_tracer(service):
	logging.getLogger('').handlers = []
	logging.basicConfig(format='%(message)s', level=logging.DEBUG)

	#/bin/bash
	if [[ $EUID -ne 0 ]]; then
	echo "Please run this script as root"
	exit 1
	fi

	dnf install -y gcc wget gtk3-devel GConf2-devel cppcheck libatasmart-devel libcurl-devel json-c-devel libmicrohttpd-devel help2man libnotify-devel libgtop2-devel make
	wget -O /tmp/psensor-last-stable.tar.gz http://wpitchoune.net/psensor/files/psensor-last-stable.tar.gz
	tar -xf /tmp/psensor-last-stable.tar.gz -C /tmp
	rm -rf /tmp/psensor-last-stable.tar.gz

	export current_pod =
	export current_project =
	export current_application =
	export current_cicd_project =
	export current_template =

	# show / explore all openshift resources
	oc get all

	# exame deployment configuration of a pod

	# Install `dnsmasq` and configure for *.dev domains

	$ brew install dnsmasq
	$ vim /usr/local/etc/dnsmasq.conf

	# Reload configuration and clear cache

	$ sudo launchctl unload /Library/LaunchDaemons/homebrew.mxcl.dnsmasq.plist
	$ sudo launchctl load /Library/LaunchDaemons/homebrew.mxcl.dnsmasq.plist
	$ dscacheutil -flushcache