The function watchdog is an OpenFaaS component. It is responsible for wrapping the real working code around a function program. The function program's requirement is only to accept input via the standard input (stdin) and print out the result, of course, to the standard output (stdout).

The API gateway (gateway) connects to function containers through an overlay network. Each function container contains the following:

• Function watchdog, fwatchdog
• A certain function program written in any language

The Dockerfile describing a function container must have the fprocess environment variable pointing to the function program name and arguments: