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すでにLinuxのロード・アベレージのことを、よくご存知かもしれません。ロード・アベレージはuptimeとtopコマンドで表示される3つの数字です。下のように表示されます。 大多数の人は多かれ少なかれ、ロード・アベレージとは何かを知っているでしょう。 3つの数字は、段階的な期間（1分、5分、15分の平均）での平均を表しています。数字が小さいほど良いことを示しています。大きい数字は、何か問題があるか、マシンの過負荷を意味します。しかし、しきい値は何でしょう？どんな時にロード・アベレージを気にしなければならないのでしょうか、そして、どんな時に緊急で、できるだけ早く解決するべきなのでしょうか？ 最初にロード・アベレージの意味について簡単に背景を説明します。最も簡単な例から始めましょう：一台のマシンに、シングル・コアのプロセッサが搭載されている場合です。 トラフィックの例え シングル・コアのCPU

Rubyのアプリケーションサーバーのエコシステムは、Unicorn、Puma、Passenger 5 の3つを中心に出来上がっています。Rubyにおいて、アプリケーションサーバーが解決しなければならない具体的な問題はなんでしょうか。どのようにして最適なアプリケーションサーバーを選択すればよいでしょうか。2019年にはこれらのアプリケーションサーバーのニーズはあるでしょうか。 この記事ではこら全てを取り上げ、Rubyの主要なアプリケーションサーバーを比較していきます。 How important is an app server's raw speed? アプリケーションサーバーそのものの速度がアプリケーションの速度に対して多くの要因となることはほとんどありません。アプリケーションコード、データベースのクエリ、HTTPコールのRubyアプリケーションサーバーとの間の応答速度が、マイクロ秒ない

ネイト・ベルコペック (@nateberkopec)  SpeedShop(詳細),Railsパフォーマンス・コンサルタンシー 要約:Rubyアプリケーションのための”スケーリング”についての情報は、毎秒数百リクエストを処理している企業によって書かれたものがほとんどです。そうではない私たちのためのスケーリングはどのようなものでしょうか？ スケーリングは敷居の高いトピックです。Rubyアプリケーションのスケーリングに関するブログやインターネットでの情報のほとんどは、毎分何万ものリクエストへのスケーリングについて書かれたものです。TwitterやShopifyの規模です。興味深いですが...Rubyでどれくらいできるか、上限を知ることはいいことです...1台よりは多いものの、せいぜい100台以下のサーバでアプリケーションを実行している、私たちのような大多数にとってはあまり役に立ちません。スケー

Looking for a fresh, 2018 approach to deploying a Rails app to AWS? We've partnered with DailyDrip on a series of videos to guide you through the process. We're covering how to Dockerize a Rails app, AWS Fargate, logging, application performance monitoring, setting up load balancing, SSL, CDN, and more. In today's video, we're setting up a background job server for our Rails app. There are several

What's the 2018 approach to deploying a Rails app to AWS? We've partnered with DailyDrip on a series of videos to guide you through the process. We'll be covering how to Dockerize a Rails app, AWS Fargate, logging, monitoring, and CDN support. Today, we will be working through a few steps to get our app Dockerized and our image pushed to a hosted Docker registry. Introduction to Docker Docker is a

It's a lot harder connecting the dots of the request lifecycle when the final response is built from a number of separate microservices. However, distributed tracing - which connects a transaction trace across microservices - is getting a lot easier. In this short tutorial, I'll show how to add distributed tracing to your Sinatra web apps via OpenTracing, a vendor-neutral tracing API, and Jaeger,

What's the 2018 approach to deploying a Rails app to AWS? We've partnered with DailyDrip on a series of videos to guide you through the process. We'll be covering how to Dockerize a Rails app, AWS Fargate, logging, monitoring, and CDN support. Today's video is the next in the series of setting up our produciton app for production use in AWS ECS. In our last video, we Dockerized the app to prepare

Your Rails app appears to be humming along just fine. But then, out of the blue, one of your most important customers emails your support team: "the site is loading slowly - is something up"? You frantically browse around the site, but everything seems fine. You double-check the charts: things look normal. Is the customer trying to trick you? Is monitoring broken? In this post, I'll show how to sl

Are folks upgrading to Rails 5? Where is the Postgres vs. MySQL battle heading? Are devs embracing Puma and concurrency? If you're curious about the above, you've come to the right place. We collect gems used on the apps we monitor at Scout to assist with debugging issues and to prioritize libraries we want to instrument. This data set, which is across thousands of apps, should be enough to grab g

The holy grail of performance profiling is finding a tool that's safe to run in production. A tool that identifies slow code as it works "in the wild". Profiling code locally is never as good as production profiling: the load is small, hardware specs are different, and I'd need to pull down a huge chunk of data to simulate things. Enter StackProf, the production safe*, holy grail of Ruby profiling

If I was teaching Server Health 101, I'd start with four key metrics: CPU Usage Memory Usage Network I/O Disk Utilization The approach for fetching these metrics on Linux hosts is tried-and-true (hint: look in the /proc folder). However, I was curious about Docker Containers: where do I access these critical metrics? What tools does Docker provide? Are there any gotchas? Read on for what I found.

I've been hearing how Docker is the new awesome, but it didn't click for me until I dug in with a practical question: if we deployed Scout via Docker, would deployment be a more pleasurable experience? My three takeaways are below. Finally, an efficient way to simulate our production environment Our production environment has 16 servers. If I attempted to simulate this locally with VirtualBox's re

When checking the amount of free memory on a Linux server, it’s easy to think you’re running out of memory when you’re not. For example, here’s the output of free -m on a server with 4GB of RAM: With a quick glance, you might start sweating. Only 39 MB of free memory? Put down the antacid – you’ve got a lot more free memory than you think. Memory Caching & Buffers Reading data from a disk is far s

UPDATED 6/7/2013 – We no longer recommend using bash -l -c to run Cron jobs with RVM. See our updated approach . This info is for Scout users, but it’s also applicable to anyone who’s wondered how to use cron together with RVM. This assumes 1) you are using bash; 2) you running you cron tasks as a non-root user (say, “deploy”). To use an RVM Ruby from cron, invoke your own bash session, like so:

Deep performance analysis and transaction traces for Ruby apps

Life as a cross-dresser must be unnerving. I could buy a wig, put some makeup on my adam’s apple. Buy a skirt. Does a sock-filled bra work for my bosom? With a bit of mood lighting, I might actually look like a woman, but it would be difficult to relax. Knowing my manhood could be exposed in a multitude of ways – some stubble on my chin, hair on my legs, forgetting to make my voice less deep, etc.