How to use Acquia Purge and Drush to clear all external caches for a site

You can use Drush and the Acquia Purge module to completely clear varnish and the Acquia CDN for a site. This can be done from the command line or in a script. 

drush p:invalidate everything --uri=example.com

The above command will clear all external caches for the example.com site. 

If you have multiple domains for one site, it will clear all of the domains under that site.

Example

You host several site with the domain names of blue.com and red.com:

First Site
blue.com
foo.blue.com
bar.blue.com
bluespecialoffer.com

Second Site
red.com
foo.red.com
bar.red.com

The following command is run:

drush p:invalidate everything --uri=blue.com

The above command will clear all caches for:  blue.com, foo.blue.com, bar.blue.com, and bluespecialoffer.com

But the domains under the Second site will not be touched. Run the same command above, replacing "blue.com" for "red.com".