1 files changed, 138 insertions, 0 deletions
diff --git a/src/util/msg_rate_delay.c b/src/util/msg_rate_delay.c
new file mode 100644
index 0000000..e21b021
--- /dev/null
+++ b/src/util/msg_rate_delay.c
@@ -0,0 +1,138 @@
+/*++
+/* NAME
+/*	msg_rate_delay 3
+/* SUMMARY
+/*	diagnostic interface
+/* SYNOPSIS
+/*	#include <msg.h>
+/*
+/*	void	msg_rate_delay(stamp, delay, log_fn, fmt, ...)
+/*	time_t	*stamp;
+/*	int	delay;
+/*	void	(*log_fn)(const char *fmt, ...);
+/*	const char *fmt;
+/* DESCRIPTION
+/*	msg_rate_delay() produces log output at a reduced rate: no
+/*	more than one message per 'delay' seconds. It discards log
+/*	output that would violate the output rate policy.
+/*
+/*	This is typically used to log errors accessing a cache with
+/*	high-frequency access but low-value information, to avoid
+/*	spamming the logfile with the same kind of message.
+/*
+/*	Arguments:
+/* .IP stamp
+/*	Time stamp of last log output; specify a zero time stamp
+/*	on the first call.  This is an input-output parameter.
+/*	This parameter is ignored when verbose logging is enabled
+/*	or when the delay value is zero.
+/* .IP delay
+/*	The minimum time between log outputs; specify zero to log
+/*	all output for debugging purposes.  This parameter is ignored
+/*	when verbose logging is enabled.
+/* .IP log_fn
+/*	The function that produces log output. Typically, this will
+/*	be msg_info() or msg_warn().
+/* .IP fmt
+/*	Format string as used with msg(3) routines.
+/* SEE ALSO
+/*	msg(3) diagnostics interface
+/* DIAGNOSTICS
+/*	Fatal errors: memory allocation problem.
+/* LICENSE
+/* .ad
+/* .fi
+/*	The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/*	Wietse Venema
+/*	IBM T.J. Watson Research
+/*	P.O. Box 704
+/*	Yorktown Heights, NY 10598, USA
+/*--*/
+
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <time.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <vstring.h>
+#include <events.h>
+
+/* SLMs. */
+
+#define STR(x) vstring_str(x)
+
+/* msg_rate_delay - rate-limit message logging */
+
+void    msg_rate_delay(time_t *stamp, int delay,
+		               void (*log_fn) (const char *,...),
+		               const char *fmt,...)
+{
+    const char *myname = "msg_rate_delay";
+    static time_t saved_event_time;
+    time_t  now;
+    VSTRING *buf;
+    va_list ap;
+
+    /*
+     * Sanity check.
+     */
+    if (delay < 0)
+	msg_panic("%s: bad message rate delay: %d", myname, delay);
+
+    /*
+     * This function may be called frequently. Avoid an unnecessary syscall
+     * if possible. Deal with the possibility that a program does not use the
+     * events(3) engine, so that event_time() always produces the same
+     * result.
+     */
+    if (msg_verbose == 0 && delay > 0) {
+	if (saved_event_time == 0)
+	    now = saved_event_time = event_time();
+	else if ((now = event_time()) == saved_event_time)
+	    now = time((time_t *) 0);
+
+	/*
+	 * Don't log if time is too early.
+	 */
+	if (*stamp + delay > now)
+	    return;
+	*stamp = now;
+    }
+
+    /*
+     * OK to log. This is a low-rate event, so we can afford some overhead.
+     */
+    buf = vstring_alloc(100);
+    va_start(ap, fmt);
+    vstring_vsprintf(buf, fmt, ap);
+    va_end(ap);
+    log_fn("%s", STR(buf));
+    vstring_free(buf);
+}
+
+#ifdef TEST
+
+ /*
+  * Proof-of-concept test program: log messages but skip messages during a
+  * two-second gap.
+  */
+#include <unistd.h>
+
+int     main(int argc, char **argv)
+{
+    int     n;
+    time_t  stamp = 0;
+
+    for (n = 0; n < 6; n++) {
+	msg_rate_delay(&stamp, 2, msg_info, "text here %d", n);
+	sleep(1);
+    }
+    return (0);
+}
+
+#endif