Aleksey Grishchenko alekgrischenko

https://t.me/pepegramming

Сегодня попался рельсовый код, в котором используются монады, сервисы и прочее. Решил сделать обзор с объяснением того, что в коде не нравится и что можно исправить.

Данный разбор основан только на личном опыте и избегает попытку написать самый идеальный код на свете. К сожалению пошарить ссылку на код не могу, потому что автор попросил опубликовать анонимно.

Исходные данные

Главная операция, которая вызывается из контроллера выглядит следующим образом:

https://t.me/pepegramming

Сегодня попался рельсовый код, в котором используются монады, сервисы и прочее. Решил сделать обзор с объяснением того, что в коде не нравится и что можно исправить.

Данный разбор основан только на личном опыте и избегает попытку написать самый идеальный код на свете. К сожалению пошарить ссылку на код не могу, потому что автор попросил опубликовать анонимно.

Исходные данные

Главная операция, которая вызывается из контроллера выглядит следующим образом:

Turning PostgreSQL into a queue serving 10,000 jobs per second

RDBMS-based job queues have been criticized recently for being unable to handle heavy loads. And they deserve it, to some extent, because the queries used to safely lock a job have been pretty hairy. SELECT FOR UPDATE followed by an UPDATE works fine at first, but then you add more workers, and each is trying to SELECT FOR UPDATE the same row (and maybe throwing NOWAIT in there, then catching the errors and retrying), and things slow down.

On top of that, they have to actually update the row to mark it as locked, so the rest of your workers are sitting there waiting while one of them propagates its lock to disk (and the disks of however many servers you're replicating to). QueueClassic got some mileage out of the novel idea of randomly picking a row near the front of the queue to lock, but I can't still seem to get more than an an extra few hundred jobs per second out of it under heavy load.

So, many developers have started going straight t

Turning PostgreSQL into a queue serving 10,000 jobs per second

RDBMS-based job queues have been criticized recently for being unable to handle heavy loads. And they deserve it, to some extent, because the queries used to safely lock a job have been pretty hairy. SELECT FOR UPDATE followed by an UPDATE works fine at first, but then you add more workers, and each is trying to SELECT FOR UPDATE the same row (and maybe throwing NOWAIT in there, then catching the errors and retrying), and things slow down.

On top of that, they have to actually update the row to mark it as locked, so the rest of your workers are sitting there waiting while one of them propagates its lock to disk (and the disks of however many servers you're replicating to). QueueClassic got some mileage out of the novel idea of randomly picking a row near the front of the queue to lock, but I can't still seem to get more than an an extra few hundred jobs per second out of it under heavy load.

So, many developers have started going straight t

Инструменты:

Видео:

Управление

	FROM ruby:2.6.1

	ARG PG_VERSION
	ARG NODE_VERSION
	ARG TINI_VERSION=v0.18.0

	RUN curl -sSL https://www.postgresql.org/media/keys/ACCC4CF8.asc \| apt-key add - \
	&& echo 'deb http://apt.postgresql.org/pub/repos/apt/ stretch-pgdg main' $PG_VERSION > /etc/apt/sources.list.d/pgdg.list \
	&& curl -o /tmp/nodejs.deb https://deb.nodesource.com/node_11.x/pool/main/n/nodejs/nodejs_$NODE_VERSION-1nodesource1_amd64.deb \
	&& apt-get update -qq \

	# PASSENGER DEV OK
	server {
	listen 80;
	listen 443 ssl http2;
	listen [::]:80;
	listen [::]:443 ssl http2;

	server_name webapp.example.com;

	location /.well-known/acme-challenge/ { alias /opt/le/.acme-challenges/; }

	upstream my-web-app-here {
	server 127.0.0.1:8080;
	}

	server {
	listen 80;
	listen 443 ssl http2;
	listen [::]:80;
	listen [::]:443 ssl http2;

	HTTP status code symbols for Rails

	Thanks to Cody Fauser for this list of HTTP responce codes and their Ruby on Rails symbol mappings.

	Status Code Symbol
	1xx Informational
	100 :continue
	101 :switching_protocols
	102 :processing

	if ENV['REDIS_ACCESS_MODE'] == 'readonly'
	class Redis
	class Client
	WRITE_COMMANDS = ::Rails.cache.data.command.map { \|a\| a[0] if a[2].include?('write') }.compact.to_set.freeze

	def process(commands)
	if commands.flatten.any? { \|c\| WRITE_COMMANDS.include?(c.to_s) }
	raise NotImplementedError, "REDIS_ACCESS_MODE is set to 'readonly', disallowing writes"
	end