The purpose of this project is to provide the server-side requirements of the Squirrel.Mac auto-update system. Note that this bears little-to-no relation to the Squirrel.Windows framework, which doesn't require an active server.

Squirrel.Mac is intended to be integrated with an application. It facilitates the process of checking for, downloading and installing updates.

The flow goes something like this:

• An application initializes Squirrel.Mac, gives it a url to hit to check for updates
• Squirrel requests this url
  • If it gets a "204 No Content" response, it assumes no update is required and reports as much to the application
  • Any other response is parsed as JSON, and the "url" field is extracted
• If an update is required, squirrel downloads the given URL, unzips it, and does various prepatatory steps
• Squirrel notifies the application an update is available
• The application presumably asks for user confirmation, then asks Squirrel to apply the update and then restart the application.

There is an existing Squirrel.Server, implemented in ruby. It wasn't sufficient for our case for the following reasons:

• It's inflexible, and only supports hosting updates for a single application
• It would require us to modify our deployment strategy to include restarting the server

This server is dead simple. It sends a 204 response as appropriate, but otherwise just proxies json files hosted elsewhere It expects two parameters:

• url - the json url to request
• version (optional) - the version of the installed application

The server performs the following steps:

• Requests the url
• Parses the response as json (handling the various error cases)
• Extracts the version field from the json response (which is actually ignored by Squrrel.Mac)
• Compares that against the version query parameter
  • If they match, send 204 No Content
  • If not, send the data along

The server makes to attempt to do any caching, since load should be fairly low.

docker build -t squirrel-server-go .
docker run -d -p 3000:3000 squirrel-server-go