Homo-Adminus Blog

It’s been a few months since we‘ve started actively using ActiveMQ queue server in our project. For some time we had pretty weird problems with it and even started thinking about switching to something else or even writing our own queue server which would comply with our requirements. The most annoying problem was the following: some time after activemq restart everything worked really well and then activemq started lagging, queue started growing and all producer processes were stalling on push() operations. We rewrote our producers from Ruby to JRuby, then to Java and still – after some time everything was in a bad shape until we restarted the queue server.

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Month ago I was on a vacation and as usual even though our hotel provided us with an internet connection on a pretty decent speeds, I wasn’t able to work there because they’ve banned all tcp ports but some major ones (like 80, 21, etc) and I needed to be able to use ssh, mysql, IMs and other non-web software.

After a short research I’ve found a pretty simple to set up and easy to use approach to such a connection problems I’d like to describe here.

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Many people know me as a nginx web server evangelist. But as (IMHO) any professional I think that it is really rewarding to know as much as possible about all the tools available on the market so every time you need to make a decision on some technical issue, you’d consider all pros and cons based on my own knowledge.

This is why when I received an email from Packt company asking if I’d like to read and review their book on Lighttpd I decided to give it a shot (I usually do not review any books because I do not always have enough time to read a book thoroughly to be able to write a review). So, here are my impressions from this book.

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Few months ago I’ve switched one of our internal projects from doing synchronous database saves of analytics data to an asynchronous processing using starling + a pool of workers. This was the day when I really understood the power of specialized queue servers. I was using database (mostly, MySQL) for this kind of tasks for years and sometimes (especially under a highly concurrent load) it worked not so fast… Few times I worked with some queue servers, but those were either some small tasks or I didn’t have a time to really get the idea, that specialized queue servers were created just to do these tasks quickly and efficiently.

All this time (few months now) I was using starling noticed really bad thing in how it works: if workers die (really die, or lock on something for a long time, or just start lagging) and queue start growing, the thing could kill your server and you won’t be able to do something about it – it just eats all your memory and this is it. Since then I’ve started looking for a better solution for our queuing, the technology was too cool to give up. I’ve tried 5 or 6 different popular solutions and all of them sucked… They ALL had the same problem – if your queue grows, this is your problem and not queue broker’s :-/ The last solution I’ve tested was ActiveMQ and either I wasn’t able to push it to its limits or it is really so cool, but looks like it does not have this memory problem. So, we’ve started using it recently.

In this small post I’d like to describe a few things that took me pretty long to figure out in ruby Stomp client: how to make queues persistent (really!) and how to process elements one by one with clients’ acknowledgments.
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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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