As is very well explained in this elaborate answer, you can customise istio's logging format in IstioOperator.
In my case, IstioOperator (when it comes to access logging configuration) looks like this
meshConfig:
accessLogEncoding: JSON
accessLogFile: /dev/stdout
i.e. no accessLogFormat specified.
However, in StackDriver, when seeing my istio-proxy logs, I see some fields NOT defined in the default format., e.g. here is a corresponding istio-proxy log entry
response_code: "200"
bytes_received: "0"
upstream_cluster: "outbound|80||myscv.default.svc.cluster.local"
downstream_remote_address: "10.17.37.1:57362"
upstream_transport_failure_reason: "-"
user_agent: "Mozilla/5.0 (compatible; Cloudflare-Traffic-Manager/1.0; +https://www.cloudflare.com/traffic-manager/; pool-id: 8474894722kdjfhg49)"
duration: "2"
x_forwarded_for: "10.15.22.1"
route_name: "-"
path: "/health"
requested_server_name: "my.public.url.net"
upstream_host: "10.15.37.29:20000"
downstream_local_address: "10.17.37.16:8443"
protocol: "HTTP/1.1"
request_id: "32455-452d-9a7a-9310-71e098fb490R"
start_time: "2021-01-20T17:27:13.021Z"
authority: "my.public.url.net"
istio_policy_status: "-"
upstream_service_time: "2"
bytes_sent: "2"
upstream_local_address: "10.43.37.16:55496"
method: "GET"
response_flags: "-"
I can see for example istio_policy_status and downstream_local_address (perhaps there are more) which are not part of the default format.
Where does istio override envoy's default access logging format?
