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Deploying Minecraft.net in 14 minutes, no way

Every time we deployed Minecraft.net it would take ~ 14 minutes, that’s a lot of time. During that time I would either do nothing or get started on something else, losing focus and probably missing any potential problems with the deploy.

That could not stand, especially considering the biggest reasons for the deployment times was easy to remove from the equation.

Reasons for our slow deploy

  1. Uploading files from the Mojang office in Sweden to Amazon EC2 in America
  2. Each server downloads its own dependencies

1. Location

Our build and deploy server was located in the office and was the culprit responsible for the first problem. Setting up a fresh Jenkins & Rundeck in the cloud was easy enough and fixed the problem for us, bringing down the deployment times to more sensible levels just by putting the servers closer to eachother. I’d say this probably took down the deployment times to 3 minutes or so, which is almost 5 times better than before.

2. Packaging

It’s not that I wasn’t happy with our new deployment times, but the second problem was in a sense more important. Each server was running the dependencies task of play (Play Framework) at application startup, fetching its dependencies and relinkling modules to where they were located on disk. This meant startup took a bit longer than strictly necessary, which in turn affected deployment times. More importantly, it meant that there was a risk that the libraries we used would change between application restarts.

A deploy should send out a self contained distribution to the server in question, anything else opens up the risk for unexplained problems during runtime. Now, there’s almost always some kind of moving parts like this, but they should be kept to a minimum. Dependencies should rarely be one of them.

It turns out Play 1 haven’t got a solution for packaging a self-contained distribution. Running play dependencies --sync --forProd will download all the needed libraries to the lib folder and remove some of the cruft that isn’t needed in production. It handles everything except modules, which for some reasons aren’t packaged with the application. Running the dependencies command actually links the modules with the location on disk where play itself is located, something that might differ from server to server.

I fixed this by packaging the modules with the distribution and adding a few extra lines to the start-script that would relink the module reference files to the once packaged with the distribution on application startup. This removed the ~20 seconds per server it took to run the dependencies command and pushed the deployment time down to ~1 minute.

Benefits and cost

It took me 2 days to do this, which is ~960 minutes (8 * 2 * 60). We do roughly 5 deploys each week, perhaps even more now that they are quicker. This means we’ll save roughly 65 minutes ((14-1) * 5) each week, or 292.5 minutes (65 * 4.5) in a month. Given this we can see that the time spent on making the deploys faster will be recuperated in ~3 months.

More importantly, I can now do deploys more lightheartedly as I know it will only take a short period of my my time. Deploying even the smallest of change becomes a no-brainer and features should no longer pile up into a big and scary deploy at the end of the sprint. Making deploys go faster might change the way I work and that’s the real advantage here.

Thanks goes out to my former collegaue Daniel Brolund who talked to me about team minutes and the way making something faster might affect more than the time spent on doing the task itself.

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