Multi-host Docker network without Swarm

Docker has several types of networks, but one of them is particularly interesting. Overlay network can span across hosts boundaries, so your web application container at HostA can easily talk to database container at HostB by its name. It doesn’t even have to know where that container is.

Unfortunately, you can’t just create overlay network and hope that it magically finds out about all participating hosts. There should be one more component in order to make that happen.

Of cause, we could use Docker in Swarm mode and problem’s solved. But we don’t have to. Configuring multi-host Docker network without Swarm is actually quite easy. Continue reading “Multi-host Docker network without Swarm”

Inter-service messaging with ZeroMQ and Node.js


ZeroMQ is small, fast and very easy to use messaging library, which works equally well both within the same process and over the network. Despite being written in C++, it has bindings for most of the languages you can come up with. And it’s free. Hurrah!

Working with ZeroMQ resembles working with TCP/UDP sockets. In fact, ZeroMQ endpoints are called sockets. You create one, bind it or connect to certain address, and then magic begins… But let’s see some code first and dive into the details as we go. Continue reading “Inter-service messaging with ZeroMQ and Node.js”

Communication between Docker containers

Having an app running from within Docker container is fun, that’s for sure. But do you know what would be even more fun? Many apps running from within containers and talking to each other. Imagine that after playing enough with microservices, you finally decided to split some real monolithic web application into:

  1. container, serving static web content, and
  2. container, serving data through some sort of RESTful API.

First container opens 80th port and, while serving html/css/js by himself, talks to the second container when data request comes.

Communicating containers

So idea is simple, but there’s one thing. How exactly those containers will communicate? How do they even find each other?

Continue reading “Communication between Docker containers”