For the reasons exposed in the previous post, I’ve begun exploring Hashicorp’s Nomad.
I am mostly interested in long running services (microservices), and the most useful article I have found out about Nomad dealing with web apps is Introducing cluster schedulers. Unfortunately, this article does not consider any load balancer in front of them, which is mandatory in order to serve several instances of the same app / service. I was not then able to find out any article adding a load balancer in front of a Nomad cluster, but several combining Docker, Consul, Consul Template, Registrator, and Nginx or HAProxy, listed below:
Among them, I’ve chosen Consul Template and Registrator, as its environment is configured and run by means of Vagrant, like the environment used in the target article on Nomad; it does not matter it’s written in Japanese, as we are currently interested just in a couple commands exposed there. WARNING: Google Translator capitalizes the first letter of every command…
Basically, I have added the VM configured in the latter article, with an HAProxy load balancer, into the set configured in the former one.
Source code available at repo
I will depict those configurations, but just providing the raw commands, as the whole explanation on them is supplied in those two excellent articles. Hence, I’d suggest taking a look at both of them before running the following tasks. Commands to run are shown below grouped in sections, each after which of these two articles they were taken from:
cd nomad-intro vagrant up vagrant status vagrant ssh nomad nomad run /vagrant/microbot.nomad
vagrant ssh haproxy1 cat /etc/haproxy/haproxy.cfg
HAProxy config file will then lack any entry at its very bottom for any Web app.
sudo consul-template\ -consul=10.7.0.15:8500\ -template=/vagrant/haproxy.ctmpl:/etc/haproxy/haproxy.cfg:"/etc/init.d/haproxy reload" cat /etc/haproxy/haproxy.cfg
Now, HAProxy config file includes an entry for each of the nine Web apps started by Nomad in the three “Docker” nodes. And invoking
curl succesively, it will show the different Docker container IDs; for example:
microbot.nomad file with your favorite text editor and change the instance value from 9 to 50. Once you’re done, tell Nomad to about our changes by running:
vagrant ssh nomad nomad run /vagrant/microbot.nomad
Hence, HAProxy config file includes an entry for each of these fifty Web apps started by Nomad in the three “Docker” nodes. And invoking
curl succesively, it will show the different Docker container IDs, such as:
You can check running services and their corresponding instances by means of Consul:
List running services:
curl -s http://10.7.0.15:8500/v1/catalog/services
List information about our
curl -s http://10.7.0.15:8500/v1/catalog/service/microbot-web-microbot
Or straight with the browser at:
And that’s it !
From this base config, I plan to explore in the near future the following paths, sharing the experience here with the corresponding articles:
I hope this information to be useful for you ! And till next post !