use microseconds for request_duration, to be consistent with mod_log_config

Author: Marius Sturm

README.md

@@ -81,6 +81,7 @@ What does the `GelfFields` string mean:
 | C         | Connection status   |
 | c         | Extract Cookie      |
 | D         | Request duration    |
+|           | (in microseconds)   |
 | f         | Requested file      |
 | H         | Protocol            |
 | h         | Remote host         |
@@ -121,9 +122,7 @@ Bundle module and configuration files to system package, e.g. for Ubuntu:
 Install dependent c libraries:
 
 ```
-  $ sudo apt-get install apache2-dev
-  $ sudo apt-get install libjson-c-dev
-  $ sudo apt-get install zlib1g-dev
+  $ sudo apt-get install apache2-dev libjson-c-dev zlib1g-dev
 ```
 
 Compile and install modules:

src/functions20.h

@@ -85,7 +85,7 @@ static const char *extract_request_time(request_rec *r, char *a)
 static const char *extract_request_duration(request_rec *r, char *a)
 {
 	apr_time_t duration = apr_time_now() - r->request_time;
-	return apr_psprintf(r->pool, "%.3lf", apr_time_usec(duration)/1000.0);
+	return apr_psprintf(r->pool, "%ld", apr_time_usec(duration));
 }
 
 static const char *extract_connection_status(request_rec *r, char *a) __attribute__((unused));

src/mod_log_gelf.c

@@ -389,7 +389,7 @@ static int log_gelf_post_config(apr_pool_t *p, apr_pool_t *plog, apr_pool_t *pte
   log_gelf_register_item(server,p,'B', extract_bytes_sent,        NULL, "_bytes_send");
   log_gelf_register_item(server,p,'C', extract_connection_status, NULL, "_connection_status");
   log_gelf_register_item(server,p,'c', extract_specific_cookie,   config->cookie, "_cookie");
-  log_gelf_register_item(server,p,'D', extract_request_duration,  NULL, "_request_duration_ms");
+  log_gelf_register_item(server,p,'D', extract_request_duration,  NULL, "_request_duration_us");
   log_gelf_register_item(server,p,'f', extract_request_file,      NULL, "_request_file");
   log_gelf_register_item(server,p,'H', extract_request_protocol,  NULL, "_request_protocol");
   log_gelf_register_item(server,p,'h', extract_remote_host,       NULL, "_remote_host");