Envoy: Support running without an admin interface

[jmillikin-stripe]

Some of Envoy's use cases, such as reverse-proxying to a non-TLS-capable backend, don't benefit much from having an admin interface available. It's just one additional port that I need to figure out how to firewall away from unauthorized access.

It'd be nice if the admin interface were made optional. Potential ways to disable it include leaving out the "admin" section of the config, or passing some special flag.

[mattklein123]

It's hard for me to imagine why anyone would ever run without the admin interface. Too useful for ops. However, not opposed to making it optional if someone does the patch.

[tlhunter]

FWIW, if one wants to "disable" the admin interface, I believe the following would work:

 "admin": {                                       
   "access_log_path": "/dev/null",                
   "address": "tcp://127.0.0.1:0"                   
 }                                               

This asks the OS to assign a random high port. It'll then only listen for requests originating within the machine.

[mattklein123]

Closing as I just don't see this getting implemented. If someone wants to step up we can reopen.