Add more control over log_format config directive

Introduces 3 new environmental variables:
 - `LOG_FORMAT`
 - `LOG_FORMAT_ESCAPE`
 - `LOG_JSON`

`LOG_FORMAT` and `LOG_FORMAT_ESCAPE` default to standard values.
When `LOG_JSON` is set, defaults are changed to: `{"time_local":"$time_iso8601","client_ip":"$http_x_forwarded_for","remote_addr":"$remote_addr","request":"$request","status":"$status","body_bytes_sent":"$body_bytes_sent","request_time":"$request_time","upstream_response_time":"$upstream_response_time","upstream_addr":"$upstream_addr","http_referrer":"$http_referer","http_user_agent":"$http_user_agent","request_id":"$request_id"}`and `json`.

See `nginx.tmpl` and https://nginx.org/en/docs/http/ngx_http_log_module.html#log_format for details

nginx.tmpl

@@ -402,7 +402,24 @@ map $proxy_x_forwarded_proto $proxy_x_forwarded_ssl {
 
 gzip_types text/plain text/css application/javascript application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript;
 
-log_format vhost '{{ or $globals.Env.LOG_FORMAT "$host $remote_addr - $remote_user [$time_local] \"$request\" $status $body_bytes_sent \"$http_referer\" \"$http_user_agent\" \"$upstream_addr\"" }}';
+
+{{- /* See https://nginx.org/en/docs/http/ngx_http_log_module.html#log_format for details and variables
+     * LOG_FORMAT_ESCAPE sets the escape part of the log format
+     * LOG_FORMAT        sets the log format
+     */}}
+{{- $logEscape := printf "escape=%s" ( or $globals.Env.LOG_FORMAT_ESCAPE `default`) }}
+{{- $logFormat := (or $globals.Env.LOG_FORMAT `$host $remote_addr - $remote_user [$time_local] "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent" "$upstream_addr"`) }}
+
+{{- if $globals.Env.LOG_JSON }}
+{{- /* LOG_JSON is a shorthand
+     * that sets logging defaults to JSON format
+     */}}
+# JSON Logging enabled (via LOG_JSON env variable)
+{{- $logEscape = printf "escape=%s" ( or $globals.Env.LOG_FORMAT_ESCAPE `json`) }}
+{{- $logFormat = (or $globals.Env.LOG_FORMAT `{"time_local":"$time_iso8601","client_ip":"$http_x_forwarded_for","remote_addr":"$remote_addr","request":"$request","status":"$status","body_bytes_sent":"$body_bytes_sent","request_time":"$request_time","upstream_response_time":"$upstream_response_time","upstream_addr":"$upstream_addr","http_referrer":"$http_referer","http_user_agent":"$http_user_agent","request_id":"$request_id"}`) }}
+{{- end }}
+
+log_format vhost {{ $logEscape }} '{{ or $globals.Env.LOG_FORMAT $logFormat }}';
 
 access_log off;
 

test/test_log_json.py

@@ -0,0 +1,14 @@
+import pytest
+
+def test_log_json(docker_compose, nginxproxy):
+    log_conf = [line for line in nginxproxy.get_conf().decode('ASCII').splitlines() if "log_format vhost escape=" in line]
+    assert "{\"time_local\":\"$time_iso8601\"," in log_conf[0]
+
+    r = nginxproxy.get("http://nginx-proxy.test/port")
+    assert r.status_code == 200
+    assert r.text == "answer from port 81\n"
+    sut_container = docker_compose.containers.get("sut")
+    docker_logs = sut_container.logs(stdout=True, stderr=True, stream=False, follow=False)
+    docker_logs = docker_logs.decode("utf-8").splitlines()
+    docker_logs = [line for line in docker_logs if "{\"time_local\":" in line]
+    assert "GET /port" in docker_logs[0]

test/test_log_json.yml

@@ -0,0 +1,15 @@
+web1:
+  image: web
+  expose:
+    - "81"
+  environment:
+    WEB_PORTS: 81
+    VIRTUAL_HOST: nginx-proxy.test
+
+sut:
+  container_name: sut
+  image: nginxproxy/nginx-proxy:test
+  volumes:
+    - /var/run/docker.sock:/tmp/docker.sock:ro
+  environment:
+    LOG_JSON: 1

test/test_log_json_format.py

@@ -0,0 +1,16 @@
+import pytest
+
+def test_log_json_format(docker_compose, nginxproxy):
+    log_conf = [line for line in nginxproxy.get_conf().decode('ASCII').splitlines() if "log_format vhost escape=" in line]
+    assert "{\"time_local\":\"$time_iso8601\"," in log_conf[0]
+
+    r = nginxproxy.get("http://nginx-proxy.test/port")
+    assert r.status_code == 200
+    assert r.text == "answer from port 81\n"
+    sut_container = docker_compose.containers.get("sut")
+    docker_logs = sut_container.logs(stdout=True, stderr=True, stream=False, follow=False)
+    docker_logs = docker_logs.decode("utf-8").splitlines()
+    docker_logs = [line for line in docker_logs if "{\"time_local\":" in line]
+    assert "GET /port" in docker_logs[0]
+
+

test/test_log_json_format.yml

@@ -0,0 +1,15 @@
+web1:
+  image: web
+  expose:
+    - "81"
+  environment:
+    WEB_PORTS: 81
+    VIRTUAL_HOST: nginx-proxy.test
+
+sut:
+  container_name: sut
+  image: nginxproxy/nginx-proxy:test
+  volumes:
+    - /var/run/docker.sock:/tmp/docker.sock:ro
+  environment:
+    LOG_FORMAT: '{"time_local":"$$time_iso8601","remote_addr":"$$remote_addr","request":"$$request","upstream_addr":"$$upstream_addr"}'