noahlz

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

branneman

Complete Courses

• Neil Gresham - Masterclass Part 1: Technique & Training [video]
• Neil Gresham - Masterclass Part 2: Skills & Tactics [video]
• Khan Academy - Human anatomy and physiology: Skeletal system [video]

Body

Warming up

• EpicTV / Louis Parkinson - How To Warm Up For Climbing [video, 2:24]
• Eric Karlsson - My Warm Up Routine [video, 11:45]
• Mani the Monkey - Stretching/Warmup Routine [video, 8:34]

alfasin

Complete Courses

• Neil Gresham - Masterclass Part 1: Technique & Training [video]
• Neil Gresham - Masterclass Part 2: Skills & Tactics [video]
• Khan Academy - Human anatomy and physiology: Skeletal system [video]

Body

Warming up

• EpicTV / Louis Parkinson - How To Warm Up For Climbing [video, 2:24]
• Eric Karlsson - My Warm Up Routine [video, 11:45]
• Mani the Monkey - Stretching/Warmup Routine [video, 8:34]

matschaffer

#!/usr/bin/env bash

URL="http://a0.awsstatic.com/pricing/1/ec2/ri-v2/linux-unix-shared.min.js"

(echo 'function callback(data) { console.log(JSON.stringify(data)); }'; curl -s "$URL") |\
  node |\
  jq -r '.config.regions[] |
      select(.region == "us-east-1") |
      .instanceTypes[] |
      [

zmmbreeze

// http://stackoverflow.com/questions/11616630/json-stringify-avoid-typeerror-converting-circular-structure-to-json/11616993#11616993
var o = {};
o.o = o;

var cache = [];
JSON.stringify(o, function(key, value) {
    if (typeof value === 'object' && value !== null) {
        if (cache.indexOf(value) !== -1) {
            // Circular reference found, discard key
            return;

telekosmos

var uniqueArray = function(arrArg) {
  return arrArg.filter(function(elem, pos,arr) {
    return arr.indexOf(elem) == pos;
  });
};

var uniqEs6 = (arrArg) => {
  return arrArg.filter((elem, pos, arr) => {
    return arr.indexOf(elem) == pos;
  });

branneman

Primitive Types & Reference Types in JavaScript

An explanation of JavaScript's pass-by-value, which is unlike pass-by-reference from other languages.

Facts

• JavaScript has 2 kinds of variable types: primitive and reference.
• A fixed amount of memory is reserved after creation of every variable.
• When a variable is copied, it's in-memory value is copied.
• Passing a variable to a function via a call also creates a copy of that variable.

Primitive Types

dreynaud

Error Handling in Practice

My experience is mostly with Java backend services in the cloud, so the advice in this post will almost certainly be biased towards this kind of error handling. But hopefully, some of it will be generally applicable and help you maintain and debug your programs in the long run.

I don't claim that these are universal best practices, but I have found these to be useful as general guidelines. As always, use your best judgment and do things that make sense in your context.

Log the whole thing

In Java, a full exception is:

Yimiprod

/**
 * This code is licensed under the terms of the MIT license
 *
 * Deep diff between two object, using lodash
 * @param  {Object} object Object compared
 * @param  {Object} base   Object to compare with
 * @return {Object}        Return a new object who represent the diff
 */
function difference(object, base) {
	function changes(object, base) {

chadmayfield

#!/bin/bash
git clone https://github.com/hashcat/hashcat.git
mkdir -p hashcat/deps
git clone https://github.com/KhronosGroup/OpenCL-Headers.git hashcat/deps/OpenCL
cd hashcat/ && make
./hashcat --version
./hashcat -b -D 1,2
./example0.sh