Envoy lua filter - http call cluster invalid. Must be configured - filter

Question

I am trying to create an envoy filter for all of my microservices deployed on a GKE cluster which is running istio.
In the filter I want to read 2 header values and send a request to an external service on web to get list of all groups that the user has authority of.
When I send the request I get "http call cluster invalid. Must be configured" error.
As per my understanding we need to register the host as cluster so that envoy understand where to send the request and I have added a value in "clusters" section of my filter.yaml file.
apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
name: authorization-filter
namespace: default
spec:
filters:
- listenerMatch:
listenerType: SIDECAR_INBOUND
listenerProtocol: HTTP
filterName: envoy.lua
filterType: HTTP
filterConfig:
inlineCode: |
function envoy_on_request(request_handle)
request_handle:logWarn("Inside filter")
local token = request_handle:headers():get("Authorization")
local partition = request_handle:headers():get("partition-id")
if token == nil or partition == nil then
request_handle:logErr("Token or Partition is empty")
request_handle:respond({[":status"] = "400",["Content-Type"] = "application/json"}, "{\"ErrorMessage\":\"Bad Request: Authorization or Partition-Id missing in headers\"}")
end
request_handle:logWarn("Sending request")
local headers, body = request_handle:httpCall(
"lua_cluster",
{
[":method"] = "GET",
[":authority"] = "example.com",
[":path"] = "/api/authorization/groups",
["Authorization"] = token,
["partition-id"] = partition
},
nil,
5000)
request_handle:headers():add("authorization-response-headers", headers)
end
clusters:
- name: lua_cluster
connect_timeout: 0.5s
type: strict_dns
lb_policy: round_robin
hosts:
- socket_address:
address: "example.com"
port_value: 8888
What am i missing here?