The Docker Engine has several parameters to tune, such as cgroups, memory, CPU, filesystems, networking, and so on. Identifying which Docker containers run on which Docker hosts is another aspect of configuration. Getting the combination of parameters to optimize our application will take time.

Replicating all the preceding configuration items to another Docker host is difficult to perform manually. We might not remember all the steps required to create a host, and it is an error-prone and slow process. Creating documentation to capture this process doesn't help either because such artifacts tend to get stale over time.

If we cannot provision new Docker hosts in a timely and reliable manner, we will have no space to scale out our Docker application. Therefore, it's important to prepare and configure our Docker hosts in a consistent...

Chef is a configuration management tool that provides a domain-specific language to model the configuration of our infrastructure. Each configuration item in our infrastructure is modeled as a resource. A resource is basically a Ruby method that accepts several parameters in a block. The following example resource describes installing the docker-engine package:

package 'docker-engine' do
  action :install
end

These resources are then written together in Ruby source files called recipes. When running a recipe against a server (a Docker host in our case), all the defined resources are executed to reach its desired state configuration.

Some Chef recipes may depend on other supplemental items, such as configuration templates and other recipes. All this information is gathered in cookbooks together with the recipes. A cookbook is a fundamental unit of distributing...

Now that we have all the components of our Chef environment set up properly, we can start writing Chef recipes to actually describe what configuration our Docker hosts should have. In addition, we will leapfrog our productivity by taking advantage of existing Chef cookbooks in the Chef ecosystem. As Docker is a popular infrastructure stack to deploy, we can use cookbooks in the wild that allow us to configure our Docker hosts. Chef cookbooks provided by the community can be found in the Chef Supermarket. We can go to http://supermarket.chef.io to discover other cookbooks that we can readily use.

In this section, we will learn how to write Chef recipes and apply them to our node. 

Now that we have a base configuration of setting up a Docker host, let us move to the next level and set up a Docker Swarm cluster automatically:

1. First, we need a way to store the Docker Swarm join token securely. We will use chef-vault as a way to store the token. To be able to use chef-vault, we will simply add it as a dependency of our cookbook in cookbooks/dockerhost/metadata.rb:

name 'dockerhost'
# ...
version '0.1.0'

depends 'docker', '~> 4.7'
depends 'chef-vault', '~> 3.1' # update here

2. Next, we will create a Chef recipe for initializing the manager node in cookbooks/dockerhost/recipes/manager.rb:

include_recipe 'dockerhost::base'

execute 'init swarm' do
  command 'docker swarm init'
  not_if 'docker info -f "{{.Swarm.LocalNodeState}}" |...

There are other general-purpose configuration management tools that allow us to configure our Docker host. The following is a short list of the other tools that we can use:

• Puppet: Refer to http://puppetlabs.com.
• Ansible: This can be found at http://ansible.com.
• CFEngine: This is available at http://cfengine.com.
• SaltStack: You can find more on this at http://saltstack.com.
• Docker Machine: This is a very specific configuration management tool that allows us to provision and configure Docker hosts in our infrastructure. More information about Docker Machine can be found on the Docker documentation page at https://docs.docker.com/machine.

If we do not want to manage our Docker host infrastructure at all, we can use Docker hosting services. Popular cloud providers started offering Docker hosts as a preprovisioned cloud image that we can use. Others offer a more...

In this chapter, we learned how to automate the configuration of our Docker deployments. Using Chef allows us to configure and provision multiple Docker hosts in scale. From this point on, we can write Chef recipes to persist all the Docker optimization techniques we will learn in this book.

In the next chapter, we will introduce instrumentation to monitor our whole Docker infrastructure and application. This will give us further feedback on how to optimize our Docker deployments better for higher performance.