Redis At 6Wunderkinder

Redis @ 6Wunderkinder - more than just a cache - Sebastian Kreutzberger, CTO

About 6Wunderkinder• Startup based in Berlin, 18 employees• VC-backed• „Wunderlist“ - free, multi-platform task app - >600k registered users, >1,6 million downloads - Android, iPhone, iPad, Web, Mac & Windows - App of the Week in 69 Apple App Stores• „Wunderkit“ - productivity platform, currently in development, „next big thing“

Redis @ Wunderlist• Wunderlist backend based on LAMP• No cache was used in the beginning• After incredible growth in userbase the marketing & BI needed statistics• Solution: Redis!• Why? Persistent, fast & super-simple

Statistics with Redis• Store 2 types of statistical data: - simple daily increments to count syncs, hits & registrations, etc. - daily Sets of user-ids who are active on that day, important for marketing to see how many people are using Wunderlist for how many days

Example<?php $cache = new Redis(); /* .... connection stuff .... */ // increment daily sync counter $key = "sync: " . date("Ymd"); // day-based key $cache->incr($key); // store current user in today’s active-users Set $key = "active: " . date("Ymd"); $cache->sAdd($key, $user_id); // get all user-ids who were active yesterday $yesterday = strtotime("-1 days 00:00"); $key = "active: " . date("Ymd", $time); $users = $cache->sMembers($key);?>

More details ...• PHPRedis as module for PHP is very fast!• Wrote cache abstraction layer for possible replacement of Redis with Memcached• Currently just do caching on user objects• Tasks & lists change too often for caching• Put a complete object into cache, not just a database row

Redis @ Wunderkit• Wunderkit uses MongoDB + async jobs• Redis is fundamental part of architecture• Even more important than database• Heavy usage of Redis Lists (a.k.a. queues)

Usage at Wunderkit• Caching of nearly all objects• Statistics• Logging• Job Queue

Logging with Redis• Wrote own PHP Error Handler• Extended it for own logging• Store PHP errors & log in Redis List• Keys are based upon day & log level• Very simple retrieval• High-performance & scalable

Job Queue I• Queue is a simple Redis List• Wrote a helper class for easy queue input• Every app server can „outsource“ processing by putting a job onto the queue• Each job contains the following data: a URL to a worker server + parameters => very simple, light-weight & scalable!

Job Queue II• Dozens of parallel PHP scripts running as daemon(!) listen for new jobs on the queue• brPop($key, $time) listens for new jobs• No concurrencies, Redis is single-threaded• Job URL is optimistically called, no waiting for response, „ﬁre & forget“ => many jobs per second!

Example Daemon<?php /* ... do crazy PHP daemon stuff here ... */ $cache = new Redis(); /* .... connection stuff .... */ while (1) // inﬁnite loop { $ret = $cache->brPop("queue", 30); // listen for 30 seconds if ($ret != false) // something new on the queue { ﬁreAsyncRequest($ret["url"], $ret["params"]); } }?>

Todos• Replacing PHP daemon with Erlang• Adding of message queue incl. callbacks• Diving into Redis Sharding• Putting even more stuff into Redis. Why? Because we love Redis!

Thanks!• Contact: Twitter: @skreutzb E-Mail: sebastiank@6wunderkinder.com Web: www.6wunderkinder.com• P.S.: We are hiring!

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Redis At 6Wunderkinder

by Sebastian Kreutzberger

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