Scribd is a top 100 site on the web and one of the largest sites built using Ruby on Rails. As one of the first rails sites to reach scale, we’ve built a lot of infrastructure and solved a lot of challenges to get Scribd to where it is today. We actively try to push the envelope and have contributed substantial work back to the open source community.
Scribd has an agile, startup culture and an unusually close working relationship between engineering and ops. You’ll regularly find cross-over work at Scribd, with ops people writing application-layer code and engineers figuring out operations-level problems. We think we’re able to make that work because of the uniquely talented people we have on the team.
To allow us to keep scaling, we’re now looking to add a strong, experienced operations guru to the team. As a member of Scribd operations, you’ll have tremendous ownership and responsibility for one of the web’s most popular applications. Because Scribd is a startup, you will wear many hats and have broader responsibility than you would at a larger company.
If you read this blog, you should already have a good sense of the kind of work you’ll be doing on this position.
The Ideal Profile
You are an experienced operations professional and have run ops at at least one large-scale website. You have comprehensive knowledge of a broad variety of system tools, from MySQL and Nginx to Squid and Memcached. You should also have strong software development skills and be well-versed in major programming languages. You should be strongly motivated, a creative solution finder, and ready to jump into the thorniest technical problems whenever necessary.
Responsibilities
- Develop and maintain all aspects of Scribd’s operations infrastructure, including system monitoring, backups, server configuration, databases, and caching systems
- Collaborate with engineering to create next generation infrastructure to support changing requirements
- Predict scaling problems before they occur and work with engineering to prevent them
- Write and debug application level ruby code
- Participate in an on-call rotation
- Quickly diagnose server problems and employ preventive measures to maintain high availability servers
Qualifications
- Bachelors degree in CS or equivalent experience
- 3-5 years of professional experience in site operations
- Strong software engineering skills, including knowledge of major programming languages
- Strong database skills, preferably with MySQL, and overall linux knowledge
- Experience with most of the following technologies: MySQL, Nginx, Ruby, Memcached, Squid, git, Solr, HBase, Postfix
- Proven ability to quickly learn and implement unfamiliar technologies
- Strong desire to work hard at a rapidly growing company
Location: You are preferably located near San Francisco, CA. Relocation assistance is designed on a per-case basis. In short, we’ll be creative to get you here.
Contact: Please send your email cover letter and resume with the subject “Your name – Senior Site Operations Engineer – via Kovyrin.net” to jobs@scribd.com or contact me directly using any of my contacts. All communication and correspondence is held in the strictest confidence to ensure that you can connect and learn more without exposure.
We use nginx and its features a lot in Scribd. Many times in the last year we needed some pretty interesting, but not supported feature – we wanted nginx X-Accel-Redirect functionality to work with remote URLs. Out of the box nginx supports this functionality for local URIs only. In this short post I want to explain how did we make nginx serve remote content via X-Accel-Redirect.
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My wife – a good web designer with 6 years of experience with web design, HTML and CSS is looking for a job. Here is some information about her:
We’re physically located in Toronto, Canada, but she has a great experience of working remotely too. So, if you need a web designer or a junior web designer, feel free to contact Tanya.
Scalexis Inc, web performance/scalability consulting firm in Toronto, is looking for a full-time consultant. Being a consulting company on the high-demand market of web application scalability consulting and high-performance web applications development, we need an employee that could perform both web application development and web application performance consulting work.
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Having a reverse-proxy web cache as one of the major infrastructure elements brings many benefits for large web applications: it reduces your application servers load, reduces average response times on your site, etc. But there is one problem every developer experiences when works with such a cache – cached content invalidation.
It is a complex problem that usually consists of two smaller ones: individual cache elements invalidation (you need to keep an eye on your data changes and invalidate cached pages when related data changes) and full cache purges (sometimes your site layout or page templates change and you need to purge all the cached pages to make sure users will get new visual elements of layout changes). In this post I’d like to look at a few techniques we use at Scribd to solve cache invalidation problems.
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Back in November 2009 I was working on a project to port Scribd.com code base to Rails 2.2 and noticed that some old plugins we were using in 2.1 were abandoned by their authors. Some of them were just removed from the code base, but one needed a replacement – that was an old plugin called acts_as_readonlyable that helped us to distribute our queries among a cluster of MySQL slaves. There were some alternatives but we didn’t like them for one or another reasons so we’ve decided to go with creating our own ActiveRecord plugin, that would help us scale our databases out. That’s the story behind the first release of DbCharmer.
Today, six months after the first release of the gem and we’ve moved it to gemcutter (which is now the official gems hosting) and we’re already at version 1.6.11. The gem was downloaded more than 2000 times. There are (at least) 10+ large users that rely on this gem to scale their products out. And (this is the most exciting) we’ve added tons of new features to the product.
Here are the main features added since the first release:
- Much better multi-database migrations support including default migrations connection changing.
- We’ve added ActiveRecord associations preload support that makes it possible to move eager loading queries to the same connection where your finder queries go to.
- We’ve improved ActiveRecord’s query logging feature and now you can see what connections your queries executed on (and yes, all those improvements are colorized
).
- We’ve added an ability to temporary remap any ActiveRecord connections to any other connections for a block of code (really useful when you need to make sure all your queries would go to some non-default slave and you do not want to mess with all your models).
- The most interesting change: we’ve implemented some basic sharding functionality in ActiveRecord which currently is being used in production in our application.
As you can see now DbCharmer helps you to do three major scalability tasks in your Rails projects:
- Master-Slave clusters to scale out your Rails models reads.
- Vertical sharding by moving some of your models to a separate (maybe even dedicated) servers and still keep using AR associations
- Horizontal sharding by slicing your models data to pieces and placing those pieces into different databases and/or servers.
So, If you didn’t check DbCharmer out yet and you’re working on some large rails project that is (or going to be) facing scalability problems, go read the docs, download/install the gem and prove them that Rails CAN scale!
Another short post just to remember the procedure for the next time I’ll be setting up a new mac. For those of my readers who do not know what Midnight Commander (aka mc) is, GNU Midnight Commander is a visual file manager, created under a heavy influence of Norton Commander file manager from dark DOS ages For more information, you can visit their web site. Now, get to the installation topic itself.
To install mc on a Mac OS X machine, you need macports installed and then first thing you’ll need to do is to install some prerequisite libraries:
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| $ sudo port install libiconv slang2 |
Next thing, download the sources from their web site and unpack them. When the sources are ready, you can configure the build:
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| $ ./configure \
--prefix=/opt/mc \
--with-screen=slang \
--enable-extcharset \
--enable-charset \
--with-libiconv-prefix=/opt/local \
--with-slang-includes=/opt/local/include \
--with-slang-libs=/opt/local/lib |
Then, normal GNU-style build and install procedure:
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| $ make
........
$ sudo make install |
And the last thing would be to add /opt/mc/bin to your PATH environment variable.
This is going to be a really short post, but for someone it could save an hour of life.
So, you’ve nothing to do and you’ve decided to play around with IPv6 or maybe you’re happened to be an administrator of a web service that needs to support IPv6 connectivity and you need to make your nginx server work nicely with this protocol.
First thing you need to do is to enable IPv6 in nginx by recompiling it with --with-ipv6 configure option and reinstalling it. If you use some pre-built package, check if your nginx already has this key enabled by running nginx -V.
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Today I’m proud to announce the first public release of our ActiveRecord database connection magic plugin: DbCharmer.
DB Charmer – ActiveRecord Connection Magic Plugin
DbCharmer is a simple yet powerful plugin for ActiveRecord that does a few things:
- Allows you to easily manage AR models’ connections (
switch_connection_to method)
- Allows you to switch AR models’ default connections to a separate servers/databases
- Allows you to easily choose where your query should go (
on_* methods family)
- Allows you to automatically send read queries to your slaves while masters would handle all the updates.
- Adds multiple databases migrations to ActiveRecord
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After the previous post in this caching related series I’ve received many questions on hardware and software configuration of our servers so in this post I’ll describe our server’s configs and the motivation behind those configs.
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