Instrumenting Ruby on Rails With Traceview

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On Building : Instrumen1ng Ruby with TraceView in 10 minutes

Peter Lombardo

h$p://blog.gameface.in h$p://www.appneta.com/blog

I’ve been a Rubyist and Linux addict for over a decade, mainly developing in Ruby and JavaScript (as well as PHP and Perl). I’m the creator of numerous soHware tools and applicaIons, most recently Password Pusher, a Ruby on Rails applicaIon to communicate passwords over the web and Gameface, a social networking plaLorm for gamers using Rails 3. When I’m not creaIng my own applicaIons, I help develop and maintain the infrastructure at OurStage and manage the Ruby community for AppNeta.

Peter Lombardo

“Gameface was created to

showcase games, the people who play them,

and the characters they play”

TraceView by AppNeta gives a unique in-‐depth view into requests even as they cross hosts and soKware stacks. Installa1on and setup of TraceView for your app is a simple two step process that can be done in 10 minutes or less.

h$p://www.appneta.com/traceview h$p://www.appneta.com/

TraceView provides deep performance monitoring of web apps.

It gives insight into your web app

performance such as this:

…and a per request drill-‐down that shows you the niOy griOy detail of where 1me is

spent in individual requests

and even end-‐user monitoring:

I run it on Gameface and PasswordPusher -‐ it’s essen1al in iden1fying problem

areas, performance boOlenecks and poor performing code. (Read: Ac1onView) Disclaimer: I authored the Ruby instrumenta6on for Traceview so I may be a bit biased. …but with good reason!

h$p://gameface.in h$p://pwpush.com/

Installa1on

Installing TraceView consists of two parts:

1)  installing the system daemon on your host, and

2)  installing the Ruby gem in your applica1on

h$p://www.appneta.com/apm-‐datasheet

Why a system daemon?

TraceView uses a system daemon to collect instrumenta6on from sources beyond applica6on code such as host metrics,

Apache or Resque.

The system daemon is installed with two commands that can be pasted into your shell. An account specific version of these commands is available in your TraceView dashboard once you create an account.

(Under SeWngs; App Configura1on; Trace New Hosts)

And the gem for your applica1on Gemfile available on RubyGems:

h$ps://rubygems.org/gems/oboe

gem 'oboe' !

TraceView func1ons by sampling a subset of all requests that go through your web applica1on. This sample rate must be set at the entry point of requests in your applica1on.

This can be a load balancer, Apache/nginx or Ruby itself. Successive hosts and soKware stacks that requests pass through will act appropriately according to upstream seWngs.!

Yes. That means requests can be traced across hosts, so6ware stacks, even track internal API calls via HTTP/SOAP/REST which make for spectacular applicaEon insight.

…But that’s another post for another Eme.

For this walkthrough we’re going to assume that you’re running a Ruby on Rails applica1on with Unicorn, Thin, Puma or any other Rack based Ruby webserver.

To instead configure Apache/nginx as the entry point, see here.

This can be a load balancer, Apache/nginx or Ruby itself. Successive hosts and soKware stacks that requests pass through will act appropriately according to upstream seWngs.!

If you setup Apache or nginx as your entry point then you can skip this part enErely. The gem will take it’s tracing instrucEons from upstream automaEcally.

Oboe!

When the gem is installed in your applica1on, it makes available !!which is a nested hash of configura1on op1ons that affect how your applica1on is instrumented.

Oboe::Config !

Oboe!

Luckily, the defaults are very smart and only a couple ini1al values need to be configured. The two required values are: Oboe::Config[:tracing_mode] = 'always' !Oboe::config[:sample_rate] = 100000 # 10% of incoming requests !

These values enable tracing (:tracing_mode) and sets the sample rate to 10% (:sample_rate). The sample_rate is calculated by the value out of one million. e.g. 300000 would equal a 30% sample rate meaning 3 out of 10 requests would be sampled. (For low traffic sites, you may want to set these values higher.)!

These values are usually set in a Rails ini1alizer for Ruby on Rails. See the OpEonal Rails IniEalizer sec1on on this page. A complete list of all configura1on op1ons for is here.!Oboe::Config !

And that’s it. Now to the good stuff…!

GeWng Performance Data

If you want to test that the oboe gem is func1onal, start-‐up a Rails console, you should see a message to stdout similar to:

Tracelytics oboe gem 1.4.0.2 successfully loaded. !

Note that on hosts that don’t have the system daemon installed, the oboe gem disables itself and outputs a message to that fact:

Deploy/restart your applica1on and you should start seeing traces show up in your TraceView dashboard aKer a couple minutes.

Unsupported Tracelytics environment (no libs). Going No-op. !

Things are moving fast for the Ruby language instrumenta1on in TraceView. We support tracing of:

memcache-‐client, memcached, dalli, mongo,

moped, mongoid, mongomapper, cassandra,

Ac1veRecord (postgres, mysql, mysql2)

…plus more.

Most recently we added support for Rack and Resque tracing. For a full-‐list of supported libraries, see this ar1cle.!

Extras: Some Random Chart Porn

A screenshot that I sent to Linode when performance unexpectedly dropped:

Linode migrated my VPS to a lesser u1lized host with evident results

(Thanks Linode):

An older issue that Gameface had with atrocious rendering 1mes:

If you haven’t tried out TraceView yet, give it a run.

You won’t be disappointed.

Note: AppNeta now offers free tracing for single projects. Check it out on their pricing page.

Instrumenting Ruby on Rails With Traceview

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