Introduces a single-flight call to a function's health
endpoint to verify that it is registered with an Istio
sidecar (Envoy) before letting the invocation through.
Results are cached for 5 seconds, before a probe is
required again.
Tested without Istio, with probe_functions environment
variable set to true, I saw a probe execute in the logs.
Fixes: #1721 for Istio users.
Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alex@openfaas.com>
Allows alerts to trigger functions to scale when they
also have an optional namespace set.
Tested e2e with Kubernetes 1.15 and a non-default namespace.
Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>
