Intermittent HTTP 0 status code

Istio version: 1.0.2 Kubernetes version: 1.11.6 CNI: Calico. Running on AWS EC2

My istio-proxy log both for the application and the istio ingress-gateway show HTTP 0 responses.

[2019-02-22T14:17:26.491Z] "POST /logs HTTP/1.1" 0 - 416 0 0 - "," "-" "73df9db4-56c5-91eb-be01-032d213963bc" "" ""

Following envoy metrics spike up when the application gives the HTTP 0 response code:

  1. Based on this, at what stage the connection is terminated?
    Client -> Ingress gateway or Ingress gateway -> Application

  2. What could cause the connection termination? Are we hitting some limit? Config error? Issue with the request?

Were you able to figure out the root cause?