Repository: public-asset-checker

Checks publicly hosted asset files against a known baseline and notifies the owning team if any require attention.

• GitHub: public-asset-checker
• Ownership: #govuk-publishing-components
• Category: Utilities
• Links:
  • Sentry (error tracking)

README

Checks either the size or version of public - third-party hosted - asset files (e.g. JavaScript, CSS etc). We use these assets on GOV.UK pages, so we want to know if the file size or version have changed. To do this we evaluate each file against a known baseline size or version. This then notifies the #user-experience-measurement-govuk Slack channel of the result or action taken.

Size checking

This compares the current file size (in bytes) with the latest known size. It uses a tolerance level to automatically update the latest known size if appropriate to minimise the amount of developer interaction and updates to the app.

Currently, the files checked are:

• https://www.googletagmanager.com/gtm.js
• https://www.googletagmanager.com/gtag/js

There are 3 possible outcomes when checking for size:

• Update - the app will automatically update the latest known size of the file to the current size, if the difference between the latest known size and current size is within the tolerance level given.

• Warning - given when the difference between the current size and the latest known size is outside of the tolerance level given.

• Same - given when the current size and the latest known size are exactly the same.

Version checking

Currently, the files checked are:

• https://cdn.speedcurve.com/js/lux.js

There are 2 possible outcomes when checking for version:

• Warning - given when the current version and the latest known version are not the same.

• Same - given when the current version and the latest known version are the same.

Screenshots

The app is hosted on Heroku.

Status page

Historical chart for file

This page is also where you can update the last known size or version value for the asset.

Example Slack notifications

Technical documentation

The app is a standard Rails application.

Before running the app

Prior to running the first time in development, and after migrating the database, you might find it useful to create some test data.

bundle exec rails db:seed

Running the test suite

bundle exec rake

Updating the Slack channel

Log into Heroku then follow this article to update the SLACK_CHANNEL environment variable in the application to the appropriate desired value.

Licence

MIT Licence