This section explains the components of OpenFaaS. The components are the API gateway, the function watchdog, and an instance of Prometheus. All are running on top of Docker Swarm or Kubernetes orchestration engines. The API gateway and the instance of Prometheus run as services, while the function watchdog runs as the part of function containers. The container runtime can be any modern version of Docker or containerd:

The client could be curl, faas-cli, or any HTTP-based client that is able to connect to the API gateway in order to invoke a function. A function container, having a function watchdog as its sidecar (an implementation pattern that lets another sidecar process run alongside the main process in the same container), lives in the cluster behind the API gateway. Each service is communicating via the main overlay network, func_functions by default: