codesnips

concurrency

go 
package quotes

import (
	"context"
	"encoding/json"
	"fmt"

Fan-In Parallel API Calls With a Bounded Worker Pool and Context Cancellation

go concurrency goroutines
by codesnips 3 tabs
ruby 
require "securerandom"

class RedisMutex
  class LockError < StandardError; end

  UNLOCK_SCRIPT = <<~LUA.freeze

Redis-Based Distributed Mutex (with TTL)

rails redis concurrency
by codesnips 2 tabs
go 
package pricecache

import (
	"context"
	"sync"

Collapse Concurrent Identical Requests in Go with singleflight

go singleflight concurrency
by codesnips 3 tabs
ruby 
class PresenceRegistry
  TTL = 30 # seconds a user counts as present without a heartbeat

  def initialize(room_id, redis: REDIS)
    @room_id = room_id
    @redis = redis

Action Cable Presence Tracking (Lightweight)

rails actioncable redis
by codesnips 3 tabs
java 
@RestController
@RequestMapping("/api/notifications")
public class NotificationController {

    private final SseEmitterRegistry registry;
    private final NotificationService service;

Push Live Notifications with Server-Sent Events in Spring Boot

spring-boot sse server-sent-events
by codesnips 3 tabs
ruby 
class ExportWriter
  def initialize(export)
    @export = export
  end

  def append(rows)

Chaining Dependent GoodJob Jobs with a Callback-Scheduled Continuation

rails good-job background-jobs
by codesnips 3 tabs
java 
@Entity
@Table(name = "idempotency_records",
       uniqueConstraints = @UniqueConstraint(columnNames = "idempotency_key"))
public class IdempotencyRecord {

    public enum Status { IN_PROGRESS, COMPLETED }

Idempotent POST Handling in Spring Boot with a Stored Idempotency-Key

spring-boot idempotency rest-api
by codesnips 3 tabs
php 
<?php

namespace App\Jobs;

use App\Models\Invoice;
use App\Services\StripeGateway;

Preventing Double-Charges in Laravel with WithoutOverlapping Job Middleware

laravel queues background-jobs
by codesnips 3 tabs
ruby 
class AddLockVersionToPosts < ActiveRecord::Migration[6.1]
  def change
    add_column :posts, :lock_version, :integer, default: 0, null: false
  end
end

Optimistic locking for concurrent updates

rails database concurrency
by Alex Kumar 2 tabs
ruby 
class Task < ApplicationRecord
  POSITION_GAP = 1024

  belongs_to :board

  scope :ordered, -> { order(:position) }

Reorder a list server-side and reflect instantly with Turbo Streams

rails hotwire turbo
by codesnips 4 tabs
lua 
-- KEYS[1] = bucket key
-- ARGV[1] = capacity, ARGV[2] = refill_rate (tokens/sec)
-- ARGV[3] = now_ms, ARGV[4] = requested tokens
local capacity    = tonumber(ARGV[1])
local refill_rate = tonumber(ARGV[2])
local now_ms      = tonumber(ARGV[3])

Token Bucket Rate Limiting in a Servlet Filter with Redis and Lua

rate-limiting token-bucket servlet
by codesnips 3 tabs
ruby 
class SlidingWindowLimiter
  Result = Struct.new(:allowed, :count, :limit, :window_ms, keyword_init: true)

  SCRIPT = <<~LUA.freeze
    local key = KEYS[1]
    local now = tonumber(ARGV[1])

Rate Limiting with Redis + Increment Expiry

rails redis reliability
by codesnips 3 tabs