feat(client): add usage report config

[fortuna]

This PR adds support for usage reporting. The config format looks like this:

transport:
  $type: tcpudp
  tcp:
      $type: shadowsocks
      endpoint: example.com:80
      <<: &cipher
        cipher: chacha20-ietf-poly1305
        secret: SECRET
      prefix: "POST "
  udp:
      $type: shadowsocks
      endpoint: example.com:53
      <<: *cipher

reporter:
  $type: http
  url: https://your-callback-server.com/outline_callback
  interval: 1h

The http reporter will send a POST request to the given URL at the beginning of the session, and then every interval.

/cc @emohandesi @62w71st

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[jyyi1]

Thanks for the implementation. Logic is clear, added a few comments.

[fortuna]

Thanks for the quick review. I'll try to address them tomorrow morning.

[jyyi1]

Thanks, LGTM now. It would be good to go after fixing the race condition caught by CI.

[fortuna]

Race condition fixed with the Go 1.25 upgrade, which also brings performance and security improvements from Go 1.23 and 1.24.

[fortuna]

FYI, I had to fix an issue caused by the upgrade to 1.25 and Go Mobile: golang/go#71827

[emohandesi]

What is the use case scenario for this reporter that sends a POST request to a server periodically?

[fortuna]

@emohandesi You guys requested it (every 24h). We can remove it though.

[emohandesi]

@emohandesi You guys requested it (every 24h). We can remove it though.

OK, I see. I thought there was another use case for it. I was trying to figure out if we could somehow take advantage of it.

[sahin141]

The new update introduced usage reporting via the HTTP reporter, which sends a POST request to the configured URL at the start of the session and then at every interval. However, I noticed that it only sends the request if the connection is successful.

With this method, is it possible to also receive error messages or connection failure reports through the same reporting mechanism?

[emohandesi]

The new update introduced usage reporting via the HTTP reporter, which sends a POST request to the configured URL at the start of the session and then at every interval. However, I noticed that it only sends the request if the connection is successful.

With this method, is it possible to also receive error messages or connection failure reports through the same reporting mechanism?

No, sending the connection error is not possible in this feature. #2036 and #2484 are implementing the error reporting feature.

[khantzawhein]

Hello, @fortuna, could you give me some insight into how this feature works and what the use case for it is?

I have been looking for this feature's documentation on Google Developer, but it seems like this feature has not been added to the documentation yet.

Edit: Doc found on https://github.com/Jigsaw-Code/outline-apps/blob/master/client/config.md