Set the response_code_details in the access log when failures occur in the transformation filter.

[pszeto]

Sometimes the transformation filter will fail parsing the body because it's not a JSON...when it fails the response_code_details is never changed from the upstream.

For example. When calling httpbin.org/xlm . It will return a 200 response code and a "response_code_details":"via_upstream" however when we add the Transformation Filter and it tries to parse the the body it fails:

2024-12-11T15:48:35.520916Z	debug	envoy filter external/envoy_gloo/source/extensions/filters/http/transformation/transformation_filter.cc:259	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] body before transformation: <?xml version='1.0' encoding='us-ascii'?>

<!--  A SAMPLE set of slides  -->

<slideshow
    title="Sample Slide Show"
    date="Date of publication"
    author="Yours Truly"
    >

    <!-- TITLE SLIDE -->
    <slide type="all">
      <title>Wake up to WonderWidgets!</title>
    </slide>

    <!-- OVERVIEW -->
    <slide type="all">
        <title>Overview</title>
        <item>Why <em>WonderWidgets</em> are great</item>
        <item/>
        <item>Who <em>buys</em> WonderWidgets</item>
    </slide>

</slideshow>	thread=21
2024-12-11T15:48:35.521006Z	debug	envoy filter external/envoy_gloo/source/extensions/filters/http/transformation/transformation_filter.cc:276	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] failure transforming [json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - invalid literal; last read: '<'	thread=21
2024-12-11T15:48:35.521035Z	trace	envoy http external/envoy/source/common/http/filter_manager.cc:1428	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] encode data called: filter=io.solo.transformation status=0thread=21
2024-12-11T15:48:35.521051Z	trace	envoy http external/envoy/source/common/http/filter_manager.cc:68	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] continuing filter chain: filter=0x265eff033c20	thread=21
2024-12-11T15:48:35.521086Z	trace	envoy http external/envoy/source/common/http/filter_manager.cc:905	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] commonEncodePrefix end_stream: false, isHalfCloseEnabled: false	thread=21
2024-12-11T15:48:35.521103Z	trace	envoy http external/envoy/source/common/http/filter_manager.cc:1243	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] encode headers called: filter=istio.stats status=0	thread=21
2024-12-11T15:48:35.521118Z	trace	envoy http external/envoy/source/common/http/filter_manager.cc:1243	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] encode headers called: filter=envoy.filters.http.cors status=0	thread=21
2024-12-11T15:48:35.521134Z	trace	envoy http external/envoy/source/common/http/filter_manager.cc:1243	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] encode headers called: filter=envoy.filters.http.fault status=0	thread=21
2024-12-11T15:48:35.521168Z	trace	envoy http external/envoy/source/common/http/filter_manager.cc:1243	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] encode headers called: filter=envoy.filters.http.grpc_stats status=0	thread=21
2024-12-11T15:48:35.521201Z	trace	envoy http external/envoy/source/common/http/filter_manager.cc:1243	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] encode headers called: filter=istio.metadata_exchange status=0	thread=21
2024-12-11T15:48:35.521265Z	debug	envoy http external/envoy/source/common/http/conn_manager_impl.cc:1825	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] encoding headers via codec (end_stream=false):
':status', '400'
'server', 'istio-envoy'
'date', 'Wed, 11 Dec 2024 15:48:35 GMT'
'content-length', '145'
'access-control-allow-origin', '*'
'access-control-allow-credentials', 'true'
'x-envoy-upstream-service-time', '3'
	thread=21

The access log has "response_code_details": "via_upstream", and "response_code": 400

{
  "response_code_details": "via_upstream",
  "downstream_local_address": "10.16.2.12:8443",
  "route_name": "insecure-echo-echo-rt-echo-configs-pszeto-mgmt-gke",
  "authority": "35.237.146.57",
  "x_forwarded_for": "136.56.75.24",
  "path": "/echo",
  "downstreamTLS": "TLSv1.3",
  "response_flags": "-",
  "x_request_id": "2670332b-2c7d-42c4-80f6-7163b6455b35",
  "upstream_cluster": "outbound|8000||in-mesh.httpbin.svc.cluster.local;",
  "requested_server_name": null,
  "upstream_tls_session_id": null,
  "bytes_received": 0,
  "client_ip": null,
  "duration": 5,
  "peerUriSan": null,
  "upstream_service_time": null,
  "upstreamTLS": "TLSv1.3",
  "user_agent": "curl/8.4.0",
  "downstream_remote_address": "136.56.75.24:50504",
  "downstream_tls_session_id": null,
  "start_time": "2024-12-11T15:48:35.516Z",
  "method": "GET",
  "upstream_host": "10.16.0.16:80",
  "upstream_transport_failure_reason": null,
  "response_code": 400,
  "localUriSan": null,
  "bytes_sent": 145,
  "upstream_local_address": "10.16.2.12:52072",
  "protocol": "HTTP/2"
}

The response_code_details should be change to something instead of via_upstream which might cause inaccurate assumption that the upstream returned the 400. Especially since the error line:

2024-12-11T15:48:35.521006Z	debug	envoy filter external/envoy_gloo/source/extensions/filters/http/transformation/transformation_filter.cc:276	[Tags: "ConnectionId":"1144","StreamId":"651067811395905973"] failure transforming [json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - invalid literal; last read: '<'	thread=21

is a debug line and when debug isn't enabled on the envoy...we never see any error condition.