Istio-1.5.4 - Getting connection failure while trying to hit external service using envoy filter

Networking
1

Hi, I am using istio 1.5.4 and trying to connect to external service (cloud function on GCP) using envoy filter. Here is the configuration, I am using -

apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: telementry-lua
  namespace: helloistio
spec:
  workloadSelector:
    labels:
      app: helloworld
  configPatches:
    # The first patch adds the lua filter to the listener/http connection manager
  - applyTo: HTTP_FILTER
    match:
      context: SIDECAR_INBOUND
      listener:
        filterChain:
          filter:
            name: "envoy.http_connection_manager"
            subFilter:
              name: "envoy.router"
    patch:
      operation: INSERT_BEFORE
      value: # lua filter specification
       name: envoy.lua
       typed_config:
         "@type": "type.googleapis.com/envoy.config.filter.http.lua.v2.Lua"
         inlineCode: |
           function envoy_on_request(request_handle)
             -- Make an HTTP call to an upstream host with the following headers, body, and timeout.
             request_handle:logWarn("telementry starts.")
             local headers, body = request_handle:httpCall(
              "lua_cluster",
              {
               [":method"] = "POST",
               [":path"] = "/telemetry-via-istio",
               [":authority"] = "europe-west1-dave-225414.cloudfunctions.net"
              },
             "{}",
             5000)
             request_handle:logWarn("telementry ends: ")
           end
  # The second patch adds the cluster that is referenced by the lua code
  # cds match is omitted as a new cluster is being added
  - applyTo: CLUSTER
    match:
      context: SIDECAR_OUTBOUND
    patch:
      operation: ADD
      value: # cluster specification
        name: "lua_cluster"
        type: STRICT_DNS
        connect_timeout: 0.5s
        lb_policy: ROUND_ROBIN
        hosts:
        - socket_address:
            protocol: TCP
            address: "europe-west1-dave-225414.cloudfunctions.net"
            port_value: 443

The cloud function, I am trying to hit is https://europe-west1-dave-225414.cloudfunctions.net/ss-test-telemetry. I am able to hit it using curl command -

curl -XPOST https://europe-west1-dave-225414.cloudfunctions.net/ss-test-telemetry
But while trying to hit it using envoy filter, I am getting connection failure error.
Please help.