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tfwrapper

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Documentation: http://www.rubydoc.info/gems/tfwrapper/

tfwrapper provides Rake tasks for working with Hashicorp Terraform 0.9 through 0.11, ensuring proper initialization and passing in variables from the environment or Ruby, as well as optionally pushing some information to Consul. tfwrapper also attempts to detect and retry failed runs due to AWS throttling or access denied errors.

Overview

This Gem provides the following Rake tasks:

• tf:init - run terraform init to pull down dependency modules and configure remote state backend. This task also checks that any configured environment variables are set and that the terraform version is compatible with this gem.
• tf:plan - run terraform plan with all variables and configuration, and TF variables written to disk. You can specify one or more optional resource address targets to pass to terraform with the -target flag as Rake task arguments, i.e. bundle exec rake tf:plan[aws_instance.foo[1]] or bundle exec rake tf:plan[aws_instance.foo[1],aws_instance.bar[2]]; see the plan documentation for more information. By default this will use terraform_landscape for formatting the plan output if the terraform_landscape gem is installed; see the section below for more information.
• tf:apply - run terraform apply with all variables and configuration, and TF variables written to disk. You can specify one or more optional resource address targets to pass to terraform with the -target flag as Rake task arguments, i.e. bundle exec rake tf:apply[aws_instance.foo[1]] or bundle exec rake tf:apply[aws_instance.foo[1],aws_instance.bar[2]]; see the apply documentation for more information. This also runs a plan first.
• tf:refresh - run terraform refresh
• tf:destroy - run terraform destroy with all variables and configuration, and TF variables written to disk. You can specify one or more optional resource address targets to pass to terraform with the -target flag as Rake task arguments, i.e. bundle exec rake tf:destroy[aws_instance.foo[1]] or bundle exec rake tf:destroy[aws_instance.foo[1],aws_instance.bar[2]]; see the destroy documentation for more information.
• tf:write_tf_vars - used as a prerequisite for other tasks; write Terraform variables to file on disk
• tf:output - run terraform output
• tf:output_json - run terraform output -json

Installation

Note: tfwrapper only supports Ruby >= 2.0.0. The effort to maintain compatibility with 1.9.3 is simply too high to justify.

Add to your Gemfile:

gem 'tfwrapper', '~> 0.6.1'

Supported Terraform Versions

tfwrapper only supports terraform 0.9-0.11. It is tested against multiple versions from 0.9.2 to 0.11.14.

Terraform Landscape

The terraform_landscape gem provides enhanced formatting of terraform plan output including colorization of changes and human-friendly diffs (i.e. diffs of JSON rendered with pretty-printing). By default plan output will be passed through terraform_landscape if the terraform_landscape gem is available. To enable this, add gem 'terraform_landscape', '~> 0.1.17' to your Gemfile. Note that we rely on an undocumented internal API of terraform_landscape to achieve this; the formatting code will fall back to unformatted output in case of an error.

If you wish to disable terraform_landscape output even when the gem is installed, pass disable_landscape: true as an option to install_tasks():

TFWrapper::RakeTasks.install_tasks('.', disable_landscape: true)

In previous versions or when terraform_landscape is not installed, the output of all terraform commands is streamed in realtime. Since terraform_landscape requires the full and complete plan output in order to reformat it, this is no longer the case. By default when terraform_landscape is installed and not disabled the plan task will not produce any output until complete, at which point it will print the landscape-formatted output all at once. This behavior can be controlled with the :landscape_progress option of install_tasks(), which takes one of the following values:

• nil, the default, to not produce any output until the command is complete at which point the landscape-formatted output will be shown.
• :dots to print a dot to STDOUT for every line of terraform plan output and then print the landscape-formatted output when complete.
• :lines to print a dot followed by a newline to STDOUT for every line of terraform plan output and then print the landscape-formatted output when complete. This is useful for systems like Jenkins that line-buffer output (and don't display anything until a newline is encountered).
• :stream to stream the terraform plan output in realtime (as was the previous behavior) and then print the landscape-formatted output when complete. Note that this will result in the output containing the complete unformatted terraform plan output, followed by the landscape-formatted output.

Usage

To use the Terraform rake tasks, require the module in your Rakefile and use the install_tasks method to set up the tasks. install_tasks takes one mandatory parameter, tf_dir specifying the relative path (from the Rakefile) to the Terraform configuration.

For a directory layout like:

.
├── bar.tf
├── foo.tf
├── main.tf
└── Rakefile

The minimal Rakefile would be:

require 'tfwrapper/raketasks'

TFWrapper::RakeTasks.install_tasks('.')

rake -T output:

rake tf:apply[target]        # Apply a terraform plan that will provision your resources; specify optional CSV targets
rake tf:destroy[target]      # Destroy any live resources that are tracked by your state files; specify optional CSV targets
rake tf:init                 # Run terraform init with appropriate arguments
rake tf:plan[target]         # Output the set plan to be executed by apply; specify optional CSV targets
rake tf:write_tf_vars        # Write PWD/build.tfvars.json

You can also point tf_dir to an arbitrary directory relative to the Rakefile, such as when your terraform configurations are nested below the Rakefile:

.
├── infrastructure
│   └── terraform
│       ├── bar.tf
│       ├── foo.tf
│       └── main.tf
├── lib
├── Rakefile
└── spec

Rakefile:

require 'tfwrapper/raketasks'

TFWrapper::RakeTasks.install_tasks('infrastructure/terraform')

Environment Variables to Terraform Variables

If you wish to bind the values of environment variables to Terraform variables, you can specify a mapping of Terraform variable name to environment variable name in the tf_vars_from_env option; these variables will be automatically read from the environment and passed into Terraform with the appropriate names. The following example sets the consul_address terraform variable to the value of the CONSUL_HOST environment variable (defaulting it to consul.example.com:8500 if it is not already set in the environment), and likewise for the environment terraform variable from the ENVIRONMENT env var.

require 'tfwrapper/raketasks'
ENV['CONSUL_HOST'] ||= 'consul.example.com:8500'

TFWrapper::RakeTasks.install_tasks(
  '.',
  tf_vars_from_env: {
    'consul_address'           => 'CONSUL_HOST',
    'environment'              => 'ENVIRONMENT',
  }
)

These variables are tested to be set in the environment with a non-empty value, and will raise an error if any are missing or empty. If some should be allowed to be missing or empty empty, pass a allowed_empty_vars list with their environment variable names.

Ruby Variables to Terraform Variables

If you wish to explicitly bind values from your Ruby code to terraform variables, you can do this with the tf_extra_vars option. Variables specified in this way will override same-named variables populated via tf_vars_from_env. In the following example, the foobar terraform variable will have a value of baz, regardless of what the FOOBAR environment variable is set to, and the hostname terraform variable will be set to the hostname (Socket.gethostname) of the system Rake is running on:

require 'socket'
require 'tfwrapper/raketasks'

ENV['FOOBAR'] ||= 'not_baz'

TFWrapper::RakeTasks.install_tasks(
  '.',
  tf_vars_from_env: {
    'foobar' => 'FOOBAR'
  },
  tf_extra_vars: {
    'foobar'   => 'baz',
    'hostname' => Socket.gethostname
  }
)

Namespace Prefixes for Multiple Configurations

If you need to work with multiple different Terraform configurations, this is possible by adding a namespace prefix and calling install_tasks multiple times. The following example will produce two sets of terraform Rake tasks; one with the default tf: namespace that acts on the configurations under tf/foo, and one with a bar_tf: namespace that acts on the configurations under tf/bar. You can use as many namespaces as you want.

Directory tree:

.
├── Rakefile
└── tf
    ├── bar
    │   └── bar.tf
    └── foo
        └── foo.tf

Rakefile:

require 'tfwrapper/raketasks'

# foo/ (default) terraform tasks
TFWrapper::RakeTasks.install_tasks('tf/foo')

# bar/ terraform tasks
TFWrapper::RakeTasks.install_tasks('tf/bar', namespace_prefix: 'bar')

rake -T output:

rake bar_tf:apply[target]    # Apply a terraform plan that will provision your resources; specify optional CSV targets
rake bar_tf:destroy[target]  # Destroy any live resources that are tracked by your state files; specify optional CSV targets
rake bar_tf:init             # Run terraform init with appropriate arguments
rake bar_tf:plan[target]     # Output the set plan to be executed by apply; specify optional CSV targets
rake bar_tf:write_tf_vars    # Write PWD/bar_build.tfvars.json
rake tf:apply[target]        # Apply a terraform plan that will provision your resources; specify optional CSV targets
rake tf:destroy[target]      # Destroy any live resources that are tracked by your state files; specify optional CSV targets
rake tf:init                 # Run terraform init with appropriate arguments
rake tf:plan[target]         # Output the set plan to be executed by apply; specify optional CSV targets
rake tf:write_tf_vars        # Write PWD/build.tfvars.json

Backend Configuration Options

install_tasks accepts a backend_config hash of options to pass as backend configuration to terraform init via the -backend-config='key=value' command line argument. This can be used when you need to pass some backend configuration in from the environment, such as a specific remote state storage path, credentials, etc.

For a simple example, assume we aren't using state environments but instead opt to use specific paths based on a ENVIRONMENT environment variable.

Our terraform configuration might include something like:

terraform {
  required_version = "> 0.9.0"
  backend "consul" {
    address = "consul.example.com:8500"
  }
}

variable "environment" {}

And the Rakefile would pass in the path to store state in Consul, as well as passing the ENVIRONMENT env var into Terraform for use:

require 'tfwrapper/raketasks'

TFWrapper::RakeTasks.install_tasks(
  '.',
  tf_vars_from_env: {'environment' => 'ENVIRONMENT'},
  backend_config: {'path' => "terraform/foo/#{ENVIRONMENT}"}
)

Calling Procs At Beginning and End of Tasks

Version 0.4.0 of tfwrapper introduced the ability to call arbitrary Ruby Procs from within the Rake tasks, at the beginning and end of the task (i.e. before and after the terraform-handling code within the task). This is accomplished via the :before_proc and :after_proc options, each taking a Proc instance.

The Procs take two positional arguments; a String containing the full, namespaced name of the Rake task it was called from, and the String tf_dir argument passed to the TFWrapper::RakeTasks class (exactly as specified).

This could be used for things such as showing the output of state after a terraform run, triggering a tfenv installation, etc.

require 'tfwrapper/raketasks'

TFWrapper::RakeTasks.install_tasks(
  '.',
  before_proc: Proc.new do |taskname, tfdir|
    next unless taskname == 'tf:apply' # example of only executing for apply task in default namespace
    puts "Executing #{taskname} task with tfdir=#{tfdir}"
  end,
  after_proc: Proc.new do |taskname, tfdir|
    puts "Executed #{taskname} task with tfdir=#{tfdir}"
  end
)

Environment Variables to Consul

tfwrapper also includes functionality to push environment variables to Consul (as a JSON object) after a successful apply. This is mainly useful when running tfwrapper from within Jenkins or another job runner, where they can be used to pre-populate user input fields on subsequent runs. This is configured via the consul_url and consul_env_vars_prefix options:

Example Terraform snippet:

variable "foo" {}
variable "bar" {}

Rakefile:

require 'tfwrapper/raketasks'

TFWrapper::RakeTasks.install_tasks(
  '.',
  tf_vars_from_env: {'foo' => 'FOO', 'bar' => 'BAR'},
  consul_url: 'http://consul.example.com:8500',
  consul_env_vars_prefix: 'terraform/inputs/foo'
)

After a successful terraform apply, e.g.:

FOO=one BAR=two bundle exec rake tf:apply

The key in Consul at terraform/inputs/foo will be set to a JSON hash of the environment variables used via tf_vars_from_env and their values:

$ consul kv get terraform/inputs/foo
{"FOO":"one", "BAR":"two"}

Sensitive Environment Variables

If you wish for certain variables to be marked as "redacted", use the tf_sensitive_vars option. This is an array of variables that will not be printed.

Note: aws_access_key and aws_secret_key will always be redacted without requiring configuration.

Example to redact the vaule for secret:

Rakefile:

require 'tfwrapper/raketasks'

TFWrapper::RakeTasks.install_tasks(
  '.',
  tf_vars_from_env: {'foo' => 'FOO', 'bar' => 'BAR', 'secret' => 'SECRET'},
  tf_sensitive_vars: ['secret']
)

Development

1. bundle install --path vendor
2. bundle exec rake pre_commit to ensure unit tests are passing and style is valid before making your changes.
3. bundle exec rake spec:acceptance to ensure acceptance tests are passing before making your changes.
4. make your changes, and write unit tests for them. If you introduced user-visible (public API) changes, write acceptance tests for them. You can run bundle exec guard to continually run unit tests and rubocop when files change.
5. bundle exec rake pre_commit to confirm your unit tests pass and your style is valid. You should confirm 100% coverage. If you wish, you can run bundle exec guard to dynamically run rspec, rubocop and YARD when relevant files change.
6. bundle exec rake spec:acceptance to ensure acceptance tests are passing.
7. Update ChangeLog.md for your changes.
8. Run bundle exec rake yard:serve to generate documentation for your Gem and serve it live at http://localhost:8808, and ensure it looks correct.
9. Open a pull request for your changes.
10. When shipped, wait for CircleCI to test. Once shipped and tests pass, merge the PR.

When running inside CircleCI, rspec will place reports and artifacts under the right locations for CircleCI to archive them. When running outside of CircleCI, coverage reports will be written to coverage/ and test reports (HTML and JUnit XML) will be written to results/.

Acceptance Tests

This gem includes some rspec-based acceptance tests, runnable via bundle exec rake spec:acceptance. These tests download a specific version of Terraform and Consul, run a local Consul server (in -dev mode), and actually run terraform via rake and confirm that Terraform both runs correctly and correctly updates state in Consul. The terraform configurations and rakefiles used can be found in spec/acceptance. The terraform configurations use only the consul provider, to remove any external dependencies other than Consul (which is already used to test remote state).

Note that the acceptance tests depend on the GNU coreutils timeout command.

Release Checklist

1. Ensure Circle tests are passing.
2. Build docs locally (bundle exec rake yard:serve) and ensure they look correct.
3. Ensure changelog entries exist for all changes since the last release.
4. Bump the version in lib/tfwrapper/version.rb
5. Change the version specifier in the "Installation" section of this README, above, as appropriate.
6. Commit those changes, open a PR for the release. Once shipped and Circle passes, merge and pull down locally.
7. Deployment is done locally, with bundle exec rake release.

License

The gem is available as open source under the terms of the MIT License.