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## channels.tla
A model of https://utcc.utoronto.ca/~cks/space/blog/programming/GoConcurrencyStillNotEasy

---- MODULE channels ----
EXTENDS Integers, TLC, Sequences

CONSTANTS NumWorkers, NumTokens

NULL == "NULL" \* Should be a constant, being lazy
Workers == 1..NumWorkers
Processes == Workers \union {0} \* Main

## subscriptions.opml
<?xml version="1.0" encoding="UTF-8"?>
<opml version="1.0">
	<head>
		<title>Subscriptions - freek@spatie.be</title>
	</head>
	<body>
		<outline text="PHP" title="PHP">
			<outline htmlUrl="http://frederickvanbrabant.com" title="frederickvanbrabant.com" xmlUrl="http://frederickvanbrabant.com/feed.xml" type="rss" text="frederickvanbrabant.com"/>
			<outline htmlUrl="http://mattallan.org" title="mattallan.org" xmlUrl="http://mattallan.org/feed.xml" type="rss" text="mattallan.org"/>
			<outline title="asked.io" xmlUrl="https://asked.io/rss" type="rss" text="asked.io"/>

## phpfunctions.sql
#standardSQL
CREATE TEMPORARY FUNCTION parseFunction(src STRING)
RETURNS ARRAY<STRING>
LANGUAGE js AS """
  var result = [];
  var regex = /([:\\w]+?)(?:\\()/g;
  var match;
  while (match = regex.exec(src)) {
    result.push(match[1]);
  }

## rapgenius-balancing.md

      
        
          
            
              
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                pbailis
                / rapgenius-balancing.md
            
            
              Last active
              July 23, 2019 12:57
            
              
                Randomized load balancing comparison
              
          
        
      
        
  
      
    RapGenius has an interesting post about Heroku's randomized load balancing, complaining about how random placement degrades performance compared to prior omniscient approaches. RapGenius ran some simulations, including an experiments with a "Choice of Two" method:

Choice of two routing is the naive method from before, with the twist that when you assign a request to a random dyno, if that dyno is already busy then you reassign the request to a second random dyno, with no regard for whether the second dyno is busy

This differs subtly but substantially from the standard "Power of Two Choices" randomized load balancing:

each [request] is placed in the least loaded of d >= 2 [Dynos] chosen independently and uniformly at random

Take a look at the difference in queue lengths below, for 200 Dynos, 100
	A model of https://utcc.utoronto.ca/~cks/space/blog/programming/GoConcurrencyStillNotEasy

	---- MODULE channels ----
	EXTENDS Integers, TLC, Sequences

	CONSTANTS NumWorkers, NumTokens

	NULL == "NULL" \* Should be a constant, being lazy
	Workers == 1..NumWorkers
	Processes == Workers \union {0} \* Main
	<?xml version="1.0" encoding="UTF-8"?>
	<opml version="1.0">
	<head>
	<title>Subscriptions - freek@spatie.be</title>
	</head>
	<body>
	<outline text="PHP" title="PHP">
	<outline htmlUrl="http://frederickvanbrabant.com" title="frederickvanbrabant.com" xmlUrl="http://frederickvanbrabant.com/feed.xml" type="rss" text="frederickvanbrabant.com"/>
	<outline htmlUrl="http://mattallan.org" title="mattallan.org" xmlUrl="http://mattallan.org/feed.xml" type="rss" text="mattallan.org"/>
	<outline title="asked.io" xmlUrl="https://asked.io/rss" type="rss" text="asked.io"/>
	#standardSQL
	CREATE TEMPORARY FUNCTION parseFunction(src STRING)
	RETURNS ARRAY<STRING>
	LANGUAGE js AS """
	var result = [];
	var regex = /([:\\w]+?)(?:\\()/g;
	var match;
	while (match = regex.exec(src)) {
	result.push(match[1]);
	}