gRPC server that accumulates configurations to update Caddy server.

Proof of concept with minimum API.

The idea is quite simple:

• Caddy starts with a regular conf but without routes:

  {
    "apps": {
      "http": {
        "servers": {
          "myserver": {
            "automatic_https": {
              "skip": []
            },
            "listen": [
              ":443"
            ],
            "routes": [
            ]
          }
        }
      }
    }
  }
  

• This gRPC server is started.
• Each application uses this server by sending requests to register their routes via gRPC calls.
• This server then notifies Caddy of a change.

To ensure that the sequence in which all apps are started doesn't influence the outcome:

• This server does not accumulate any data until it gets a minimum conf from Caddy.
  • Keeps querying Caddy until it responds.
    • If Caddy returns an empty conf during polling, gRPC server pushes initial conf (unless --init=false).
    • Never queries Caddy again when conf received is not empty.
    • Implication: If base conf of Caddy is changed, this gRPC server will also have to be restarted.
• Each app that wants to register its route has to use the same Route.id (think domain name as a good candidate).
• Each app has to periodically announce itself with its route registration, since:
  • We can't request each app of its conf.
  • Caddy can (re)start at any moment and should be able to receive each app's route from scratch.
  • This gRPC server can also be restarted at any moment.