Currently, some log messages that would be useful at info or warn level
are kept at debug level because there is no way to throttle them, and a
guest could otherwise flood the host logs.
Add a logmsg_ratelimit() macro that uses per-call-site static variables
to independently track each call site's rate. It allows up to
LOG_RATELIMIT_BURST (5) messages per LOG_RATELIMIT_INTERVAL (1 second)
window, then prints a suppression notice. When a new window opens and
messages were suppressed, the count is reported after the next allowed
message.
Link: https://bugs.passt.top/show_bug.cgi?id=134
Signed-off-by: Anshu Kumari
---
v4:
- Print suppression notice immediately after the last allowed message,
not on the next call, to avoid confusion with unrelated messages
in between.
- Add Link: tag before Signed-off-by
---
log.h | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
diff --git a/log.h b/log.h
index 6ceb686..dbab006 100644
--- a/log.h
+++ b/log.h
@@ -48,6 +48,50 @@ void logmsg_perror(int pri, const char *format, ...)
passt_exit(EXIT_FAILURE); \
} while (0)
+#define LOG_RATELIMIT_INTERVAL 1 /* Default rate limit window in seconds */
+#define LOG_RATELIMIT_BURST 5 /* Max messages per window per call site */
+
+/**
+ * logmsg_ratelimit() - Log a message with rate limiting
+ * @fn: Logging function name (e.g. warn, info, debug)
+ * @now: Current timestamp
+ */
+#define logmsg_ratelimit(fn, now, ...) \
+ do { \
+ static unsigned int rl_suppressed_; \
+ static unsigned int rl_printed_; \
+ static time_t rl_last_; \
+ \
+ if ((now)->tv_sec - rl_last_ > LOG_RATELIMIT_INTERVAL) {\
+ rl_last_ = (now)->tv_sec; \
+ rl_printed_ = 0; \
+ } \
+ \
+ if (rl_printed_ < LOG_RATELIMIT_BURST) { \
+ fn(__VA_ARGS__); \
+ if (rl_suppressed_) { \
+ fn("(suppressed %u similar messages)", \
+ rl_suppressed_); \
+ rl_suppressed_ = 0; \
+ } \
+ rl_printed_++; \
+ if (rl_printed_ == LOG_RATELIMIT_BURST) \
+ fn("(suppressing further similar" \
+ " messages)"); \
+ } else { \
+ rl_suppressed_++; \
+ } \
+ } while (0)
+
+#define err_ratelimit(now, ...) \
+ logmsg_ratelimit(err, now, __VA_ARGS__)
+#define warn_ratelimit(now, ...) \
+ logmsg_ratelimit(warn, now, __VA_ARGS__)
+#define info_ratelimit(now, ...) \
+ logmsg_ratelimit(info, now, __VA_ARGS__)
+#define debug_ratelimit(now, ...) \
+ logmsg_ratelimit(debug, now, __VA_ARGS__)
+
extern int log_file;
extern int log_trace;
extern bool log_conf_parsed;
--
2.53.0