Pantheon YAML Configuration Files

Hook into platform workflows and manage advanced site configuration via the pantheon.yml file. Add it to the root of your site's codebase, and deploy it along with the rest of your code.

For reference implementations see example.pantheon.yml and Quicksilver Example Scripts.

Advanced Site Configuration

Include api_version

Define the api_version property in order for pantheon.yml to be valid:

api_version: 1

Protected Web Paths

Protect files and directories inside of your docroot from public web access with protected_web_paths. For example, the following ensures that a visitor to https://example.com/example.txt or https://example.com/example_directory/any_nested_file receives Access Denied (403):

protected_web_paths:
  - /example.txt
  - /example_directory

Considerations

• Specify the exact path; no regex or wildcards allowed
• Paths begin with a leading / and are relative to your docroot
• Limited to 24 protected paths
• You may not be able to protect files or paths with special characters
• Wait a few seconds for changes to take effect

Enforce HTTPS + HSTS

HTTPS adds a layer of encryption that prevents others from snooping on or tampering with traffic to your site. HTTP Strict Transport Security (HSTS) instructs browsers to only connect via HTTPS and helps protect websites against protocol downgrade attacks and cookie hijacking.

Pantheon sites (using the default Pantheon upstreams) created or updated on or after September 30 2019 default to enforcing HTTPS via a redirect and a short, 5-minute duration, HSTS header. You can override the default with the enforce_https directive in a site-specific pantheon.yml file.

Use of the HSTS header is defined by the enforce_https directive, and takes five possible values which are handled by Pantheon as shown below:

For example, to set enforce_https as off:

enforce_https: off

Considerations

• Use of full or full+subdomains should be treated as a commitment. HSTS headers are cached by browsers for the duration of the max-age period. If your site is unable to serve HTTPS (e.g. by moving to a host that doesn't support HTTPS), visitors will be unable to access your site.
• Any option with +subdomains should only be used if you want to enforce HTTPS for all subdomains, even those not connected to Pantheon.
• To prepare your site to serve all content via HTTPS, follow the Switching Sites from HTTP to HTTPS doc.

Test Your Site's HSTS Configuration for an A+ Rating

SSL Labs provides a free, online service that you can use to test your Site's configuration. In order to obtain an A+ rating, a long-duration HSTS header using the full or full+subdomains value is required.

1. To test your configuration, select a short-duration HSTS header (transitional or transitional+subdomains), before committing to the long-duration HSTS header.
2. When you're comfortable that HSTS works as expected in the Live environment, send the long-duration HSTS header by moving to full or full+subdomains.

Nested Docroot

Nest your docroot one level beneath your code repository in a directory named web:

web_docroot: true

The name of the nested directory is not configurable.

For more information, see Serving Sites from the Web Subdirectory.

PHP Version

Override the upstream's default PHP version with the php_version property. PHP version is managed in version control and deployed along with the rest of your site's code to encourage testing before making a change on your Live site.

For example, to override the upstream default value at the site level to PHP 7:

php_version: 7.0

Considerations

• Upgrading PHP Versions may require you to resolve compatibility issues with your site's codebase.
• Drupal and PHP 7 require Drush 7 or greater.
• From time to time, we will roll out a new default version of PHP, which will be available to apply as One-click update in the Dashboard. If you are overriding the default, make sure to remove php_version from pantheon.yml as soon as possible to ensure you don't miss the latest recommended PHP version.
• You'll always be able to test new default PHP version in Dev and Test before deploying Live.

Drush Version

Add drush_version to the top level of the pantheon.yml file to configure the Drush version used when making calls remotely on Pantheon:

drush_version: 8

For more information, see Managing Drush Versions on Pantheon.

Filemount Path

Pantheon provides a cloud-based filesystem to store user-generated content and other website files. By default, we create a symlink to this filesystem at /sites/default/files (Drupal) or /wp-content/uploads (WordPress), but you can change the location with the filemount variable:

filemount: /files

This creates a new symlink to the filesystem at the specified location. Note that this setting is only recommended when creating a custom upstream. Instead, consider using a symlink as described in Non-Standard Files Locations.

Complete the following before deploying filemount (required):

1. Reconfigure Drupal 8, Drupal 7, or WordPress to use the new path

2. Add path to the .gitignore file

3. Configure a private subdirectory of the new path within protected_web_paths

Considerations

• Recommended usage limited to Custom Upstream Configurations in pantheon.upstream.yml
• Path must be relative to the site's docroot
• Specify the exact path; limited selection of valid paths:
  • /files
  • /sites/default/files
  • /wp-content/uploads

Quicksilver Platform Integration Hooks

Use the pantheon.yml file to define scripts you want executed automatically when a particular workflow is triggered on Pantheon by you or a teammate. For example, you can write a script to post a message to Slack whenever code is pushed to the Site Dashboard.

For more information, see Automate your Workflow with Quicksilver Platform Integration Hooks and check our growing set of Platform Integration guides demonstrating Quicksilver hooks.

Custom Upstream Configurations

Add a pantheon.upstream.yml file to your organization's Custom Upstream to set default configurations for all downstream sites. The same properties described above can be used in this file. In addition, it is also possible to define a deploy_product Quicksilver hook here; however other Quicksilver workflows are not supported.

This file should only be edited in the Custom Upstream repository where it is defined. Similarly, the Custom Upstream repository should not define a pantheon.yml file; it should place all configuration settings in the upstream file instead.

When the same configuration value is defined in both files, the value from pantheon.yml will override the value from pantheon.upstream.yml at the site-level.

Troubleshooting

"Changes to pantheon.yml detected, but there was an error while processing it"

The Platform will automatically reject a commit that includes a pantheon.yml error. The error message will resemble:

remote: PANTHEON ERROR:
remote:
remote: Changes to `pantheon.yml` detected, but there was an error while processing it:
remote:
remote:
remote: Version '2' is not a valid pantheon.yml version!
remote: Valid versions are: 1

While our parser will reject a pantheon.yml that is invalid, it won't necessarily give you the exact reason the file is invalid. Please refer to the examples above for exact syntax, or try running the contents of your pantheon.yml file through a YAML linter.

Deploying Configuration Changes to Multidev

Changes made to pantheon.yml file on a branch are not detected when creating the Multidev environment for that branch. As a workaround, make some modification to pantheon.yml file and re-commit to the Multidev environment. You will then receive a notice indicating configuration changes have been detected and applied to the Multidev environment:

remote:
remote: PANTHEON NOTICE:
remote:
remote: Changes to `pantheon.yml` detected.
remote:
remote: Successfully applied `pantheon.yml` to the 'new-feature' environment.
remote:
remote:

Deploying Hotfixes

Changes made to pantheon.yml are not detected when deployed as a hotfix. As a workaround, make a modification to your pantheon.yml file in a development environment (e.g, add a code comment), then deploy up to production using the standard Pantheon workflow.

See Also

• Automating and Integrating your Pantheon Workflow with Quicksilver Platform Hooks
• Upgrade PHP Versions