What is istio-proxy access log mean?

Question

I am trying to troubleshoot my service by looking at the istio-proxy access log (it logs every access). However, I can't find any documentation that explains the meaning of each entry in the log.

For example

[2018-12-20T11:09:42.302Z] "GET / HTTP/1.1" 200 - 0 614 0 0 "10.32.96.32" "curl/7.54.0" "17b8f245-af00-4379-9f8f-a4dcd2f38c01" "foo.com" "127.0.0.1:8080"

What does log above mean?

Updated

I've tried Vadim's answer, but I couldn't find the log format data. Here's the output json file. Is there anything that I miss? I am using istio-1.0.0

Answer 1

Istio proxy access log's configuration is defined as part of envoy.http_connection_manager or envoy.tcp_proxy filters. To see it's configuration, run:

istioctl proxy-config listeners <your pod> -n <your namespace> -o json

Search for access_log of envoy.http_connection_manager for HTTP and access_log of envoy.tcp_proxy for TCP.

You will see something like this:

 "filters": [
                {
                    "name": "envoy.http_connection_manager",
                    "config": {
                        "access_log": [
                            {
                                "config": {
                                    "format": "[%START_TIME%] \"%REQ(:METHOD)% %REQ(X-ENVOY-ORIGINAL-PATH?:PATH)% %PROTOCOL%\" %RESPONSE_CODE% %RESPONSE_FLAGS% %BYTES_RECEIVED% %BYTES_SENT% %DURATION% %RESP(X-ENVOY-UPSTREAM-SERVICE-TIME)% \"%REQ(X-FORWARDED-FOR)%\" \"%REQ(USER-AGENT)%\" \"%REQ(X-REQUEST-ID)%\" \"%REQ(:AUTHORITY)%\" \"%UPSTREAM_HOST%\" %UPSTREAM_CLUSTER% %UPSTREAM_LOCAL_ADDRESS% %DOWNSTREAM_LOCAL_ADDRESS% %DOWNSTREAM_REMOTE_ADDRESS% %REQUESTED_SERVER_NAME%\n",
                                    "path": "/dev/stdout"

Check the log attributes definitions here

If access_log's format is not specified in the output above, the default format is used.