Question: Generic cluster for DispatchHttpCall?

[jonfriesen]

I'd like to make calls using proxywasm.DispatchHttpCall(...) to various URLs. Is it possible to have a cluster in the envoy config that will use the :authority header and forward the request on?

I was exploring something like:

  clusters:
  - name: dynamic_forward_proxy_cluster
    lb_policy: CLUSTER_PROVIDED
    cluster_type:
      name: envoy.clusters.dynamic_forward_proxy
      typed_config:
        "@type": type.googleapis.com/envoy.extensions.clusters.dynamic_forward_proxy.v3.ClusterConfig
        dns_cache_config:
          name: dynamic_forward_proxy_cache_config
          dns_lookup_family: V4_ONLY

but end up getting errors like:

[debug][router] [source/common/router/router.cc:514] [Tags: "ConnectionId":"0","StreamId":"1203041025397599499"] cluster 'dynamic_forward_proxy_cluster' match for URL '/post'
[debug][upstream] [source/extensions/clusters/dynamic_forward_proxy/cluster.cc:396] host httpbin.org:80 not found
[debug][upstream] [source/common/upstream/cluster_manager_impl.cc:2010] no healthy host for HTTP connection pool
[debug][http] [source/common/http/async_client_impl.cc:106] async http request response headers (end_stream=false):
':status', '503'
'content-length', '19'
'content-type', 'text/plain'

[14954665][error][wasm] [source/extensions/common/wasm/context.cc:1193] wasm log: dispatch http call failed: error status returned by host: internal failure
[14954665][critical][wasm] [source/extensions/common/wasm/context.cc:1196] wasm log: Error dispatching payload: error status returned by host: internal failure

with headers like:

	hs := [][2]string{
		{"accept", "*/*"},
		{":authority", "httpbin.org"},
		{":method", "POST"},
		{":path", "/post"},
		{":scheme", "http"},
		{"Content-Type", "application/json"},
	}

[mathetake]

#451