HTTP: added route logging.

-  Configuration: added "/config/settings/http/log_route".

   Type: bool
   Default: false

   This adds configurability to the error log.  It allows enabling and
   disabling logs related to how the router performs selection of the
   routes.

-  HTTP: logging request line.

   Log level: [notice]

   The request line is essential to understand which logs correspond to
   which request when reading the logs.

-  HTTP: logging route that's been discarded.

   Log level: [info]

-  HTTP: logging route whose action is selected.

   Log level: [notice]

-  HTTP: logging when "fallback" action is taken.

   Log level: [notice]

Closes: <https://github.com/nginx/unit/issues/758>
Link: <https://github.com/nginx/unit/pull/824>
Link: <https://github.com/nginx/unit/pull/839>
Suggested-by: Timo Stark <t.stark@nginx.com>
Suggested-by: Mark L Wood-Patrick <mwoodpatrick@gmail.com>
Suggested-by: Liam Crilly <liam@nginx.com>
Tested-by: Liam Crilly <liam@nginx.com>
Acked-by: Artem Konev <a.konev@f5.com>
Cc: Andrew Clayton <a.clayton@nginx.com>
Cc: Andrei Zeliankou <zelenkov@nginx.com>
Reviewed-by: Zhidao Hong <z.hong@f5.com>
Signed-off-by: Alejandro Colomar <alx@nginx.com>

src/nxt_h1proto.c

@@ -507,6 +507,7 @@ nxt_h1p_conn_request_init(nxt_task_t *task, void *obj, void *data)
 
             r->conf = joint;
             skcf = joint->socket_conf;
+            r->log_route = skcf->log_route;
 
             if (c->local == NULL) {
                 c->local = skcf->sockaddr;
@@ -653,6 +654,11 @@ nxt_h1p_header_process(nxt_task_t *task, nxt_h1proto_t *h1p,
     r->path = &h1p->parser.path;
     r->args = &h1p->parser.args;
 
+    if (nxt_slow_path(r->log_route)) {
+        nxt_log(task, NXT_LOG_NOTICE, "http request line \"%V %V %V\"",
+                r->method, &r->target, &r->version);
+    }
+
     r->fields = h1p->parser.fields;
 
     ret = nxt_http_fields_process(r->fields, &nxt_h1p_fields_hash, r);