evhttp_request_set_on_complete_cb to be more specific about what the …

…function actually does and usage

http.c

@@ -3846,10 +3846,10 @@ evhttp_request_set_error_cb(struct evhttp_request *req,
 
 void
 evhttp_request_set_on_complete_cb(struct evhttp_request *req,
-    void (*cb)(struct evhttp_request *, void *), void *arg)
+    void (*cb)(struct evhttp_request *, void *), void *cb_arg)
 {
 	req->on_complete_cb = cb;
-	req->on_complete_cb_arg = arg;
+	req->on_complete_cb_arg = cb_arg;
 }
 
 /*

include/event2/http.h

@@ -555,14 +555,19 @@ void evhttp_request_set_error_cb(struct evhttp_request *,
     void (*)(enum evhttp_request_error, void *));
 
 /**
- * Set a on request complete callback.
+ * Set a callback to be called on request completion of evhttp_send_* function.
  *
- * Receive a callback on request completion.  This callback is triggered once
- * the request is complete and all resources associated with the request will
- * be released.
+ * The callback function will be called on the completion of the request after
+ * the output data has been written and before the evhttp_request object
+ * is destroyed. This can be useful for tracking resources associated with a
+ * request (ex: timing metrics).
+ *
+ * @param req a request object
+ * @param cb callback function that will be called on request completion
+ * @param cb_arg an additional context argument for the callback
  */
-void evhttp_request_set_on_complete_cb(struct evhttp_request *,
-    void (*)(struct evhttp_request *, void *), void *);
+void evhttp_request_set_on_complete_cb(struct evhttp_request *req,
+    void (*cb)(struct evhttp_request *, void *), void *cb_arg);
 
 /** Frees the request object and removes associated events. */
 void evhttp_request_free(struct evhttp_request *req);