From 821863053ea9f0fa5d99d227ecaa918766e86550 Mon Sep 17 00:00:00 2001
From: Ben Pfaff <blp@nicira.com>
Date: Wed, 4 Mar 2009 17:30:20 -0800
Subject: [PATCH] vlog: Add functions for testing a rate-limit without emitting
 a message.

This allows clients to avoid doing work to construct a rate-limited
message until they know that the message will actually be displayed.
---
 lib/vlog.c | 30 +++++++++++++++++++-----------
 lib/vlog.h | 12 ++++++++----
 2 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/lib/vlog.c b/lib/vlog.c
index e23d0173..08f1e4eb 100644
--- a/lib/vlog.c
+++ b/lib/vlog.c
@@ -622,14 +622,12 @@ vlog(enum vlog_module module, enum vlog_level level, const char *message, ...)
     va_end(args);
 }
 
-void
-vlog_rate_limit(enum vlog_module module, enum vlog_level level,
-                struct vlog_rate_limit *rl, const char *message, ...)
+bool
+vlog_should_drop(enum vlog_module module, enum vlog_level level,
+                 struct vlog_rate_limit *rl)
 {
-    va_list args;
-
     if (!vlog_is_enabled(module, level)) {
-        return;
+        return true;
     }
 
     if (rl->tokens < VLOG_MSG_TOKENS) {
@@ -649,21 +647,31 @@ vlog_rate_limit(enum vlog_module module, enum vlog_level level,
                 rl->first_dropped = now;
             }
             rl->n_dropped++;
-            return;
+            return true;
         }
     }
     rl->tokens -= VLOG_MSG_TOKENS;
 
-    va_start(args, message);
-    vlog_valist(module, level, message, args);
-    va_end(args);
-
     if (rl->n_dropped) {
         vlog(module, level,
              "Dropped %u messages in last %u seconds due to excessive rate",
              rl->n_dropped, (unsigned int) (time_now() - rl->first_dropped));
         rl->n_dropped = 0;
     }
+    return false;
+}
+
+void
+vlog_rate_limit(enum vlog_module module, enum vlog_level level,
+                struct vlog_rate_limit *rl, const char *message, ...)
+{
+    if (!vlog_should_drop(module, level, rl)) {
+        va_list args;
+
+        va_start(args, message);
+        vlog_valist(module, level, message, args);
+        va_end(args);
+    }
 }
 
 void
diff --git a/lib/vlog.h b/lib/vlog.h
index 8785851c..ca66309b 100644
--- a/lib/vlog.h
+++ b/lib/vlog.h
@@ -121,6 +121,8 @@ void vlog_set_levels(enum vlog_module, enum vlog_facility, enum vlog_level);
 char *vlog_set_levels_from_string(const char *);
 char *vlog_get_levels(void);
 bool vlog_is_enabled(enum vlog_module, enum vlog_level);
+bool vlog_should_drop(enum vlog_module, enum vlog_level,
+                      struct vlog_rate_limit *);
 void vlog_set_verbosity(const char *arg);
 
 /* Configuring log facilities. */
@@ -161,10 +163,7 @@ void vlog_rate_limit(enum vlog_module, enum vlog_level,
 #define VLOG_IS_INFO_ENABLED() vlog_is_enabled(THIS_MODULE, VLL_INFO)
 #define VLOG_IS_DBG_ENABLED() vlog_is_enabled(THIS_MODULE, VLL_DBG)
 
-/* Convenience macros.  To use these, define THIS_MODULE as a macro that
- * expands to the module used by the current source file, e.g.
- *      #include "vlog.h"
- *      #define THIS_MODULE VLM_netlink
+/* Convenience macros for rate-limiting.
  * Guaranteed to preserve errno.
  */
 #define VLOG_ERR_RL(RL, ...) VLOG_RL(RL, VLL_ERR, __VA_ARGS__)
@@ -172,6 +171,11 @@ void vlog_rate_limit(enum vlog_module, enum vlog_level,
 #define VLOG_INFO_RL(RL, ...) VLOG_RL(RL, VLL_INFO, __VA_ARGS__)
 #define VLOG_DBG_RL(RL, ...) VLOG_RL(RL, VLL_DBG, __VA_ARGS__)
 
+#define VLOG_DROP_ERR(RL) vlog_should_drop(THIS_MODULE, VLL_ERR, RL)
+#define VLOG_DROP_WARN(RL) vlog_should_drop(THIS_MODULE, VLL_WARN, RL)
+#define VLOG_DROP_INFO(RL) vlog_should_drop(THIS_MODULE, VLL_INFO, RL)
+#define VLOG_DROP_DBG(RL) vlog_should_drop(THIS_MODULE, VLL_DBG, RL)
+
 /* Command line processing. */
 #define VLOG_OPTION_ENUMS OPT_LOG_FILE
 #define VLOG_LONG_OPTIONS                                   \
-- 
2.30.2