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/*++
/* 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
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