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

aelkz

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)    

aelkz

#/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

aelkz

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.

aelkz

# 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

aelkz

#!/usr/bin/env bash
set -e
# Uninstall Java 9 off the bat, so we can fix our local installation
if brew cask ls --versions "java" &>/dev/null; then
  echo "Uninstalling Java"
  brew cask uninstall java
fi
# Install jenv, java8 and java9
brew install jenv
brew cask install caskroom/versions/java8

aelkz

#!/bin/sh

#
# a simple way to parse shell script arguments
# 
# please edit and use to your hearts content
# 


ENVIRONMENT="dev"

aelkz

1. Copy m3u8 link

2. Run command

echo "Enter m3u8 link:";read link;echo "Enter output filename:";read filename;ffmpeg -i "$link" -bsf:a aac_adtstoasc -vcodec copy -c copy -crf 50 $filename.mp4

aelkz

m3u8 Downloading

1. Open Chrome Developer tools and click the Network tab.
2. Navigate to the page with the video and get it to start playing.
3. Filter the list of files to "m3u8".
4. Find master.m3u8 or index.m3u8 and click on it.
5. Save the file to disk and look inside it.
6. If the file contains a single m3u8 master url, copy that one instead.
7. Run the program m3u8x.
8. Paste the same m3u8 url in both textboxes (URL and Quality URL) and click "Headers" and set the referral url and user-agent from the request as found in Chrome.

aelkz

Working with ansible-vault

---

I've been using a lot of Ansible lately and while almost everything has been great, finding a clean way to implement ansible-vault wasn't immediately apparent.

What I decided on was the following: put your secret information into a vars file, reference that vars file from your task, and encrypt the whole vars file using ansible-vault encrypt.

Let's use an example: You're writing an Ansible role and want to encrypt the spoiler for the movie Aliens.