Next, they needed to choose a runtime for the containers, but "there were very few deployments in production at that time," says Lallemand. They experimented with Docker
but decided to go with rkt
. Lallemand explains that for BlaBlaCar, it was "much simpler to integrate things that are on rkt." At the time, the project was still pre-v1.0, so "we could speak with the developers of rkt and give them feedback. It was an advantage." Plus, he notes, rkt was very stable, even at this early stage.
Once those decisions were made that summer, the company came up with a plan for implementation. First, they formed a task force to create a workflow that would be tested by three of the 10 members on Lallemand’s team. But they took care to run regular workshops with all 10 members to make sure everyone was on board. "When you’re focused on your product sometimes you forget if it’s really user friendly, whether other people can manage to create containers too," Lallemand says. "So we did a lot of iterations to find a good workflow."
After establishing the workflow, Lallemand says with a smile that "we had this strange idea that we should try the most difficult thing first. Because if it works, it will work for everything." So the first project the team decided to containerize was the database. "Nobody did that at the time, and there were really no existing tools for what we wanted to do, including building container images," he says. So the team created their own tools, such as dgr
, which builds container images so that the whole team has a common framework to build on the same images with the same standards. They also revamped the service-discovery tools Nerve
; their versions, Go-Nerve
, were written in Go and built to be more efficient and include new features. All of these tools were open-sourced.
At the same time, the company was working to migrate its entire platform to containers with a deadline set for Christmas 2015. With all the work being done in parallel, BlaBlaCar was able to get about 80 percent of its production into containers by its deadline with live traffic running on containers during December. (It’s now at 100 percent.) "It’s a really busy time for traffic," says Lallemand. "We knew that by using those new servers with containers, it would help us handle the traffic."
In the middle of that peak season for carpooling, everything worked well. "The biggest impact that we had was for the deployment of new services," says Lallemand. "Before using containers, we had to first deploy a new server and create configurations with Chef. It would take sometimes a day, sometimes two, just to create a new service. And with all the tooling that we made around the containers, copying a new service is a matter of minutes. So it’s really a huge gain. For the developers, it means they can focus only on the features that they’re developing and not on the infrastructure or the hour they would test their code, or the hour that it would get deployed."