cilindrox

CPU: percentage of limit

A lot of people land when trying to find out how to calculate CPU usage metric correctly in prometheus, myself included! So I'll post what I eventually ended up using as I think it's still a little difficult trying to tie together all the snippets of info here and elsewhere.

This is specific to k8s and containers that have CPU limits set.

To show CPU usage as a percentage of the limit given to the container, this is the Prometheus query we used to create nice graphs in Grafana:

sum(rate(container_cpu_usage_seconds_total{name!~".*prometheus.*", image!="", container_name!="POD"}[5m])) by (pod_name, container_name) /

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/**  I was told to write comments, but thats erelephant
 *      _    _
 *     / \__/ \_____
 *    /  /  \  \    `\
 *    )  \''/  (     |\
 *    `\__)/__/'_\  / `
 *       //_|_|~|_|_|
 *       ^""'"' ""'"'
 */

cilindrox

Introduction

Some people like to run tools such as test runners outside their editor. Perhaps manually or perhaps via some file watching utility. They then review the output, switch back to their editor, and navigate to the appropriate location.

I prefer to explicitly invoke an external program from my editor, review the output, and allow my editor to jump to the first error. As well as storing a list of the locations of any other errors, a list that I may

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iptables n'at

Source NAT

Source NAT changes the source address in IP header of a packet. It may also change the source port in the TCP/UDP headers. The typical usage is to change the a private (rfc1918) address/port into a public address/port for packets leaving your network. Available only in the POSTROUTING chain in iptables.

Syntax

iptables -t nat -A POSTROUTING -i eth1 -j SNAT --to-source 1.2.3.4[:port]

Example

cilindrox

A composable pattern for pure state machines with effects

State machines are everywhere in interactive systems, but they're rarely defined clearly and explicitly. Given some big blob of code including implicit state machines, which transitions are possible and under what conditions? What effects take place on what transitions?

There are existing design patterns for state machines, but all the patterns I've seen complect side effects with the structure of the state machine itself. Instances of these patterns are difficult to test without mocking, and they end up with more dependencies. Worse, the classic patterns compose poorly: hierarchical state machines are typically not straightforward extensions. The functional programming world has solutions, but they don't transpose neatly enough to be broadly usable in mainstream languages.

Here I present a composable pattern for pure state machiness with effects,

cilindrox

If you're using macOS, run these commands:

pkill "ZoomOpener"; rm -rf ~/.zoomus; touch ~/.zoomus && chmod 000 ~/.zoomus;
pkill "RingCentralOpener"; rm -rf ~/.ringcentralopener; touch ~/.ringcentralopener && chmod 000 ~/.ringcentralopener;

These two commands do the same thing for the two most popular "brands" of Zoom (Zoom, and RingCentral). They first kill the hidden server if it is running, and then regardless deletes it from its hidden directory if it exists there. Finally they create an empty file

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body {
  font-family: Liberation Sans, Arial, sans-serif;
  background-color: #fffaf7;
  line-height: 1.3;
}
main {
  max-width: 70ch;
  padding: 2ch;
  margin: auto;
}

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// Copyright 2010 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build OMIT

package main

import (
	"container/heap"

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// link to "iw3mp.exe" +set dedicated 1 +set sv_punkbuster 1 +exec dedicated.cfg +map_rotate
// Put this file under CoD4/main install folder

set sv_hostname "chorilan"

// Security
set g_password ""
set rcon_password "changeMe!"

// Maximum Clients

cilindrox

PSQL

Magic words:

psql -U postgres

If run with -E flag, it will describe the underlaying queries of the \ commands (cool for learning!).

Most \d commands support additional param of __schema__.name__ and accept wildcards like *.*