A repeatable test environment with Terraform and chef-solo

Posted in: Cloud, Technical Track

I have been refreshing my Chef skills, and have been looking for ways to incorporate simple strategies for deployment of temporary lab environments in the cloud, that provide a secure, flexible, repeatable, and cost-effective set of resources for testing code. One of the challenges of working in a Vagrant environment is how to protect our client’s intellectual property (i.e. the code we wish to test, in our case a Chef cookbook) when it is distributed around the globe on our consultants’ laptops. I wanted to tackle the problem simply, one step at a time.

As I see it, cloud services offer a flexible and secure environment in which policies can be managed, costs can be minimized, and access can be controlled. Three things are needed:

  1. A standard, flexible, easy to use deployment framework and template / example environment library
  2. An access control and environmental separation framework that allows lab resources to be deployed securely
  3. A set of templates and policies to manage and control shared infrastructure dependencies and to retire idle resources

Number one is how I spent my Sunday afternoon last week, with this as the result:

https://github.com/kpeder/theseeker

Following the README should get you started with deploying the host if you are familiar with Terraform already. This template uses AWS services, but the concept is portable to any of the multiple providers supported by Terraform.

What this is good for:

I think that the benefits of this approach to testing deployment code are clear, but to highlight:

  • We can add the cloud provider’s management framework and services to our test framework, providing a secure location and environmental separation as needed for testing of intellectual property (i.e. code).
  • We can store our test data in the cloud securely, and access it when required by keeping it on persistent storage (EBS in this case).
  • We use templated environments to ensure consistent and repeatable deployments for developers and engineers to collaborate on, as we would with a locally deployed Vagrant test environment.
  • We leverage scale and flexibility in the cloud to create practical testing environments that match our needs and those of our customers.
  • We leverage automation and environmental policies to ensure resource usage is minimized to that required for testing activities; systems are shut down and minimal storage costs incurred when the environments are not in use.

Prerequisites:

In preparation, you require an Amazon Web Services account with:
– an EC2 keypair with the private key available on your local host (usually in ~/.ssh/ somewhere).
– an IAM access key and secret access key for the AWS account that will be used to deploy.

To deploy the lab:

  1. Install Terraform (https://terraform.io) from Hashicorp (https://hashicorp.com) and ensure that the ‘terraform’ directory is somewhere in your path.
  2. Create a build directory and change into it. Clone the repository and change to the project directory. I always set up a remote (origin) at this point in git. We’ll be using the master branch.
  3. Per the README, ensure that you create a ‘terraform.tfvars’ file with 600 permissions and add your authentication token data in the format provided. (This file is excepted in the ‘.gitignore’ to prevent accidental upload of authentication tokens to the repository).
  4. Run ‘terraform plan’ and review the output. If no errors, run ‘terraform apply’. Your environment should start to build in AWS, and Terraform will create some local state files in the working project directory.
  5. Provisioning output will be displayed as the build and bootstrap progresses, with output of the commands run in the remote-exec provisioner section of template file ‘theseeker.tf’. (The Seeker‘ is a song by The Who if you are wondering, and IMO the best name ever given to a test host). Review this file to see what’s happening.
  6. When provisioning completes, we should have a functioning instance running Amazon Linux in US-West/Oregon, by default. If you change the region (in ‘variables.tf’) then don’t forget that you must also update your AMIs (also in ‘variables.tf’) to match the proper region. I’ve used this AMI in my example, specifically the HVM EBS-backed image.
  7. The public DNS address is output by Terraform. Connect to this using your private EC2 key using ‘ssh -i ~/.ssh/myec2key -l ec2-user fully.qualified.name’.

Note:

If you inspect the template noted in step 5 you will notice that the host is configured to not delete the EBS volume on termination, meaning that after instance termination the EBS volume will be preserved and can be booted from again (so we don’t lose our chef cookbook work between deployments). Do note however that for each node that is freshly provisioned using Terraform, a new volume will be created. If you wish to destroy the volume on creation, update the following section and change the value to ‘true’, however keep in mind that terminating the instance will terminate the data in your ‘chef-repo’.

root_block_device {
delete_on_termination = false
}

Chef-solo usage:

Now that we’ve logged into our host, let’s change directory to ‘chef-repo’ and have a look…

  1. From the ‘chef-repo’ directory, knife and knife-solo are already configured. You can see the configuration in ‘.chef/knife.rb’.
  2. The ‘cookbooks’ and ‘site-cookbooks’ directories are in the default cookbook path. No roles are configured. There is one node, ‘localhost’, under the nodes directory.
  3. To see the node configuration, run ‘knife node –local-mode list’… ‘localhost‘ is returned.
  4. Let’s have a look at the run list for this node, using ‘knife node –local-mode show localhost’… ‘recipe[ntp::default]‘ is returned in the Run List.
  5. We can see from the output that the run list for the node contains the ‘ntp::default’ recipe as configured by the remote-exec provisioner in the template.
  6. If we wanted to add additional recipes to the run list for the node, we can use ‘knife node –local-mode run_list add localhost ‘recipe[cookbook::recipe]”.
  7. Finally, we can apply the ntp recipe to the node localhost using ‘knife solo cook ec2-user@localhost -i ~/.ssh/mykey’. Note that a second run of the same command will yield a different result, as the new configuration has already been applied by Chef.
  8. When done with the environment, log out of the host and issue a ‘terraform destroy’ command. Type ‘yes’ in response to the confirmation message and Terraform will dismantle the lab and terminate the instance.

Other notes:

Don’t forget that you can now boot the instance from the EC2 console by selecting the volume we created as the new instance’s root (boot) volume.

Chef-solo also supports Berkshelf for dependency management, just install to your ‘chef-repo’ directory and chef-solo will act accordingly.

It’s worth noting that in my research I found that the the chef client now supports local mode operation and will eventually replace chef-solo for headless operation.

A great next step to get going with Terraform templates would be to create a new template file to deploy a second aws instance and then configure it with knife-solo from our first host. To ensure connectivity between nodes, ssh access must be available. To accomplish this simply, we can add the new host to the existing host group, ‘sg_theseeker_access’ which allows ssh login from anywhere by default. Again, refer to the instance template in step 5 in the deployment section above for an example of this.

In my next blog I will be describing a similar, templated Terraform environment that uses Ansible and Ambari Blueprints to deploy a 6+ node Hortonworks Hadoop cluster in ~45 minutes, ready to receive data and code for testing. For a sneak preview, see this github repository and dive into the README.

Have fun!

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Data Developer - Kick Analytics @Pythian

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