Here is a great article on using dot to document microservices:
I have forked and extended the gist to:
This is all you need to generate the below image from the above text:
dot architecture.dot -Tpng > architecture.png

You can even add annotations to the lines by adding [label=”My Link”] to the connection before.
These are ideal to add to the README.md of github projects.
I especially like the idea of having a diagram with the source to create it under source control.
This requires you to install graphviz which can be done:
# Mac
brew install graphviz
# Windows
choco install graphviz
# Linux
sudo apt-get install graphviz
For the purists who want to keep their machines clean:
# Docker
cat file.dot | docker container run --rm -i vladgolubev/dot2png > file.png