Homo-Adminus Blog

Since the day one when I joined Scribd, I was thinking about the fact that 90+% of our traffic is going to the document view pages, which is a single action in our documents controller. I was wondering how could we improve this action responsiveness and make our users happier.

Few times I was creating a git branches and hacking this action trying to implement some sort of page-level caching to make things faster. But all the time results weren’t as good as I’d like them to be. So, branches were sitting there and waiting for a better idea.
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Today I’ve managed to finish initial version of our bounces-handler package we use for mailing-related stuff in Scribd.

Bounces-handler package is a simple set of scripts to automatically process email bounces and ISP‘s feedback loops emails, maintain your mailing blacklists and a Rails plugin to use those blacklists in your RoR applications.

This piece of software has been developed as a part of more global work on mailing quality improvement in Scribd.com, but it was one of the most critical steps after setting up reverse DNS records, DKIM and SPF.

The package itself consists of two parts:

• Perl scripts to process incoming email:
  • bounces processor — could be assigned to process all your bounce emails
  • feedback loops messages processor — more specific for Scribd, but still – could be modified for your needs (will be released soon).
• Rails plugin to work with mailing blacklists

For more information, please check our README file. If you have any questions, comments or suggestions, please leave them here as a comments and I’ll try to reply as soon as possible.

If you’ve ever worked in companies with 5-10+ servers and it was your responsibility to install new boxes, change some configuration files and install new software on many boxes you definitely know how painful this work is. Every time you need to change something on 3-5-100 boxes, you go there and make those changes. Most experienced of us used some weird scripts to perform some task on many boxes or used some stuff like dsh. Even with those tricks I’d never wish this work to anyone.

While I was working in Galt, I’ve asked our junior admin to check out puppet and try to use it on our servers. After a week of screaming he’s managed to install and configure it and said “Wow! This is what we definitely need!”. Since then he was using it and was happy :-). But, unfortunately (for me) I’ve never tried it and when I’ve changed my job and started doing the same old (but not good) things like dsh and for+ssh I’ve started thinking: “Stop! Try puppet – maybe it is what you need!”. And what can i say? Yes! This is what every admin needs! Today we’ve deployed our next web server (we do it pretty often) and it was done with puppet – pretty painlessly and quickly.

So, what is puppet? Let me quote their site:

Puppet lets you centrally manage every important aspect of your system using a cross-platform specification language that manages all the separate elements normally aggregated in different files, like users, cron jobs, and hosts, along with obviously discrete elements like packages, services, and files.

Puppet’s simple declarative specification language provides powerful classing abilities for drawing out the similarities between hosts while allowing them to be as specific as necessary, and it handles dependency and prerequisite relationships between objects clearly and explicitly. Puppet is written entirely in Ruby.

Basically, puppet is a tool which lets you describe whatever you’d like about your server(s) and deploy your configuration (configs, packages, files, directories, cron jobs, user accounts, ssh keys, etc) to any number of servers you need. You can describe some simple parts of your system (like “apache”, “nginx”, “rails”, “useful_gems”, “admin-ssh-keys”, etc) and then describe your servers using those terms (like machine X = apache+rails+useful_gems+admin_ssh_keys). When it is done, you’ll be able to deploy all this stuff with one command!

So, if you’re struggling with deploying some changes on many servers or, even, have only a few of them, I’d recommend to try puppet – it could save you a lots of time and nerves.

P. S. When you’ll try to use it – do not give up for a few days – it is hard to change your way of thinking and start writing correct and convenient scripts using puppet’s language.

This will be one of those posts I’d like to publish primarily to be able to coma back later and check it out instead of reading docs again 🙂

So, we have a server with two (or more) network interfaces are we need to be able to use more than one interface in our VDS machines. How do we set it up?

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It’s been a long time since we’ve started this project and it is time to make a checkpoint. So, I’ve decided to release final 1.0 version and make 1.X branch stable while all serious development with deep architectural changes will be done 2.X branch (trunk at this moment).

Changes from previous release:

• Perl semaphores implementation caused huge memory leaks (mmmd_mod).
• Now we do not send any commands to hard offline hosts with dead TCP/IP stack to prevent mointoring problems for other hosts.
• Removed legacy StartSlave method from agent code which caused problems on some Perl versions
• Added a few fixes to prevent non-exclusive roles from moving. This caused internal status structures to be corrupted.
• Made all mysql checks properly report errors occurring (previously they were resulting in an OK response). Thanks to Phillip Pearson.
• Some memory leaks found in mysql checkers and as a quick fix we’ve added an idea of “Maximum Checks Before Restart” to all checkers. If you want some checker to restart after N checks, simply add “restart after N” to your checker declaration.
• Added some more docs to the project site.

New version can be obtained here or from the project’s SVN repository.