WIP Adding proxying support

[karl-ravn]

Sometimes this service needs to be hidden behind friendly lines and not exposing the exact URL for the favicon resource that was requested. Sometimes you get mixed results when your own service runs https but the favicon is supposed to be downloaded from http - causing everything to break and emit errors.

Running the server with DOWNLOAD_MODE=proxy makes the server download and forward the resource to the user.

[galgolan]

This is a great and useful feature!
I started the code with DOWNLOAD_MODE=proxy but the server behaves the same...

[karl-ravn]

Sorry for not responding back earlier. When the server is started with DOWNLOAD_MODE=proxy, it's supposed to almost behave the same. However, there are two main differences:

with current non-proxy mode:

59001:~ karrav$ curl --head http:'//localhost:3000/icon?url=www.marketwatch.com&size=32'
HTTP/1.1 302 Found
Cache-Control: max-age=2592000
Content-Type: text/html; charset=utf-8
Location: https://mw4.wsj.net/mw5/content/logos/favicon.ico
Date: Thu, 05 Sep 2019 11:43:17 GMT

with proxy-mode:

59001:~ karrav$ curl --head http:'//localhost:3000/icon?url=www.marketwatch.com&size=32'
HTTP/1.1 200 OK
Cache-Control: max-age=2592000
Date: Thu, 05 Sep 2019 11:39:17 GMT
Content-Type: image/png

The main difference here would be that the icon binary will be sent over the request instead of being redirected to there.

[mat]

Thanks @karl-ravn for this contribution and sorry for getting back so late :(

I, too, think this is useful for some people.

Some suggestion before we merge:

• 1. Calling the env variable SERVER_MODE with values download (this PR) and redirect (current and default behavior) would be a clearer naming IMO. What do you think?
• 2. Could you add this to list of env variable settings to the Readme (https://github.com/mat/besticon#configuration)
• 3. Do you think you can write a test for this?
• 4. Also, feel free to add yourself to https://github.com/mat/besticon#contributors

[karl-ravn]

Ok, I've done 1,2 and 4 but writing a good unit test for this... it's a bit tricky since I'm not really a Go developer..

[immanuelfodor]

I've just found this project searching for a favicon proxy, this PR would be so great to have :)

[mat]

Thanks @karl-ravn for adding this feature.

I'm going to add a test and will release a new version soon, too.

[csandman]

@mat is there any way to access this var when using the docker image? It appears its not currently available, and I don't see SERVER_MODE in the docker file.

[mat]

@csandman Good catch, I failed to release a new version of the Docker image! The latest docker image is now up to date and contains support for SERVER_MODE: https://hub.docker.com/r/matthiasluedtke/iconserver/latest