src/time.c

/*
 * Time calculation functions.
 *
 * Copyright 2000-2011 Willy Tarreau <w@1wt.eu>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 */

#include <unistd.h>
#include <sys/time.h>

#include <haproxy/api.h>
#include <haproxy/time.h>
#include <haproxy/ticks.h>
#include <haproxy/tools.h>

THREAD_LOCAL unsigned int   now_ms;          /* internal date in milliseconds (may wrap) */
THREAD_LOCAL struct timeval now;             /* internal date is a monotonic function of real clock */
THREAD_LOCAL struct timeval date;            /* the real current date */
struct timeval start_date;      /* the process's start date */
THREAD_LOCAL struct timeval before_poll;     /* system date before calling poll() */
THREAD_LOCAL struct timeval after_poll;      /* system date after leaving poll() */

static unsigned long long now_offset;        /* global offset between system time and global time */
volatile unsigned long long global_now;      /* common monotonic date between all threads (32:32) */
volatile unsigned int global_now_ms;         /* common monotonic date in milliseconds (may wrap) */

static THREAD_LOCAL unsigned int iso_time_sec;     /* last iso time value for this thread */
static THREAD_LOCAL char         iso_time_str[34]; /* ISO time representation of gettimeofday() */

/*
 * adds <ms> ms to <from>, set the result to <tv> and returns a pointer <tv>
 */
struct timeval *_tv_ms_add(struct timeval *tv, const struct timeval *from, int ms)
{
	tv->tv_usec = from->tv_usec + (ms % 1000) * 1000;
	tv->tv_sec  = from->tv_sec  + (ms / 1000);
	while (tv->tv_usec >= 1000000) {
		tv->tv_usec -= 1000000;
		tv->tv_sec++;
	}
	return tv;
}

/*
 * compares <tv1> and <tv2> modulo 1ms: returns 0 if equal, -1 if tv1 < tv2, 1 if tv1 > tv2
 * Must not be used when either argument is eternity. Use tv_ms_cmp2() for that.
 */
int _tv_ms_cmp(const struct timeval *tv1, const struct timeval *tv2)
{
	return __tv_ms_cmp(tv1, tv2);
}

/*
 * compares <tv1> and <tv2> modulo 1 ms: returns 0 if equal, -1 if tv1 < tv2, 1 if tv1 > tv2,
 * assuming that TV_ETERNITY is greater than everything.
 */
int _tv_ms_cmp2(const struct timeval *tv1, const struct timeval *tv2)
{
	return __tv_ms_cmp2(tv1, tv2);
}

/*
 * compares <tv1> and <tv2> modulo 1 ms: returns 1 if tv1 <= tv2, 0 if tv1 > tv2,
 * assuming that TV_ETERNITY is greater than everything. Returns 0 if tv1 is
 * TV_ETERNITY, and always assumes that tv2 != TV_ETERNITY. Designed to replace
 * occurrences of (tv_ms_cmp2(tv,now) <= 0).
 */
int _tv_ms_le2(const struct timeval *tv1, const struct timeval *tv2)
{
	return __tv_ms_le2(tv1, tv2);
}

/*
 * returns the remaining time between tv1=now and event=tv2
 * if tv2 is passed, 0 is returned.
 * Must not be used when either argument is eternity.
 */
unsigned long _tv_ms_remain(const struct timeval *tv1, const struct timeval *tv2)
{
	return __tv_ms_remain(tv1, tv2);
}

/*
 * returns the remaining time between tv1=now and event=tv2
 * if tv2 is passed, 0 is returned.
 * Returns TIME_ETERNITY if tv2 is eternity.
 */
unsigned long _tv_ms_remain2(const struct timeval *tv1, const struct timeval *tv2)
{
	if (tv_iseternity(tv2))
		return TIME_ETERNITY;

	return __tv_ms_remain(tv1, tv2);
}

/*
 * Returns the time in ms elapsed between tv1 and tv2, assuming that tv1<=tv2.
 * Must not be used when either argument is eternity.
 */
unsigned long _tv_ms_elapsed(const struct timeval *tv1, const struct timeval *tv2)
{
	return __tv_ms_elapsed(tv1, tv2);
}

/*
 * adds <inc> to <from>, set the result to <tv> and returns a pointer <tv>
 */
struct timeval *_tv_add(struct timeval *tv, const struct timeval *from, const struct timeval *inc)
{
	return __tv_add(tv, from, inc);
}

/*
 * If <inc> is set, then add it to <from> and set the result to <tv>, then
 * return 1, otherwise return 0. It is meant to be used in if conditions.
 */
int _tv_add_ifset(struct timeval *tv, const struct timeval *from, const struct timeval *inc)
{
	return __tv_add_ifset(tv, from, inc);
}

/*
 * Computes the remaining time between tv1=now and event=tv2. if tv2 is passed,
 * 0 is returned. The result is stored into tv.
 */
struct timeval *_tv_remain(const struct timeval *tv1, const struct timeval *tv2, struct timeval *tv)
{
	return __tv_remain(tv1, tv2, tv);
}

/*
 * Computes the remaining time between tv1=now and event=tv2. if tv2 is passed,
 * 0 is returned. The result is stored into tv. Returns ETERNITY if tv2 is
 * eternity.
 */
struct timeval *_tv_remain2(const struct timeval *tv1, const struct timeval *tv2, struct timeval *tv)
{
	return __tv_remain2(tv1, tv2, tv);
}

/* tv_isle: compares <tv1> and <tv2> : returns 1 if tv1 <= tv2, otherwise 0 */
int _tv_isle(const struct timeval *tv1, const struct timeval *tv2)
{
	return __tv_isle(tv1, tv2);
}

/* tv_isgt: compares <tv1> and <tv2> : returns 1 if tv1 > tv2, otherwise 0 */
int _tv_isgt(const struct timeval *tv1, const struct timeval *tv2)
{
	return __tv_isgt(tv1, tv2);
}

/* tv_update_date: sets <date> to system time, and sets <now> to something as
 * close as possible to real time, following a monotonic function. The main
 * principle consists in detecting backwards and forwards time jumps and adjust
 * an offset to correct them. This function should be called once after each
 * poll, and never farther apart than MAX_DELAY_MS*2. The poll's timeout should
 * be passed in <max_wait>, and the return value in <interrupted> (a non-zero
 * value means that we have not expired the timeout).
 *
 * tv_init_process_date() must have been called once first, and
 * tv_init_thread_date() must also have been called once for each thread.
 *
 * An offset is used to adjust the current time (date), to figure a monotonic
 * local time (now). The offset is not critical, as it is only updated after a
 * clock jump is detected. From this point all threads will apply it to their
 * locally measured time, and will then agree around a common monotonic
 * global_now value that serves to further refine their local time. As it is
 * not possible to atomically update a timeval, both global_now and the
 * now_offset values are instead stored as 64-bit integers made of two 32 bit
 * values for the tv_sec and tv_usec parts. The offset is made of two signed
 * ints so that the clock can be adjusted in the two directions.
 */
void tv_update_date(int max_wait, int interrupted)
{
	struct timeval min_deadline, max_deadline, tmp_now;
	unsigned int old_now_ms;
	unsigned long long old_now;
	unsigned long long new_now;
	ullong ofs, ofs_new;
	uint sec_ofs, usec_ofs;

	gettimeofday(&date, NULL);

	/* compute the minimum and maximum local date we may have reached based
	 * on our past date and the associated timeout. There are three possible
	 * extremities:
	 *    - the new date cannot be older than before_poll
	 *    - if not interrupted, the new date cannot be older than
	 *      before_poll+max_wait
	 *    - in any case the new date cannot be newer than
	 *      before_poll+max_wait+some margin (100ms used here).
	 * In case of violation, we'll ignore the current date and instead
	 * restart from the last date we knew.
	 */
	_tv_ms_add(&min_deadline, &before_poll, max_wait);
	_tv_ms_add(&max_deadline, &before_poll, max_wait + 100);

	ofs = HA_ATOMIC_LOAD(&now_offset);

	if (unlikely(__tv_islt(&date, &before_poll)                    || // big jump backwards
		     (!interrupted && __tv_islt(&date, &min_deadline)) || // small jump backwards
		     __tv_islt(&max_deadline, &date))) {                  // big jump forwards
		if (!interrupted)
			_tv_ms_add(&now, &now, max_wait);
	} else {
		/* The date is still within expectations. Let's apply the
		 * now_offset to the system date. Note: ofs if made of two
		 * independent signed ints.
		 */
		now.tv_sec  = date.tv_sec  + (int)(ofs >> 32); // note: may be positive or negative
		now.tv_usec = date.tv_usec + (int)ofs;         // note: may be positive or negative
		if ((int)now.tv_usec < 0) {
			now.tv_usec += 1000000;
			now.tv_sec  -= 1;
		} else if (now.tv_usec >= 1000000) {
			now.tv_usec -= 1000000;
			now.tv_sec  += 1;
		}
	}

	/* now that we have bounded the local time, let's check if it's
	 * realistic regarding the global date, which only moves forward,
	 * otherwise catch up.
	 */
	old_now = global_now;
	old_now_ms = global_now_ms;

	do {
		tmp_now.tv_sec  = (unsigned int)(old_now >> 32);
		tmp_now.tv_usec = old_now & 0xFFFFFFFFU;

		if (__tv_islt(&now, &tmp_now))
			now = tmp_now;

		/* now <now> is expected to be the most accurate date,
		 * equal to <global_now> or newer.
		 */
		new_now = ((ullong)now.tv_sec << 32) + (uint)now.tv_usec;
		now_ms = __tv_to_ms(&now);

		/* let's try to update the global <now> (both in timeval
		 * and ms forms) or loop again.
		 */
	} while (((new_now != old_now    && !_HA_ATOMIC_CAS(&global_now, &old_now, new_now)) ||
		  (now_ms  != old_now_ms && !_HA_ATOMIC_CAS(&global_now_ms, &old_now_ms, now_ms))) &&
		 __ha_cpu_relax());

	/* <now> and <now_ms> are now updated to the last value of global_now
	 * and global_now_ms, which were also monotonically updated. We can
	 * compute the latest offset, we don't care who writes it last, the
	 * variations will not break the monotonic property.
	 */

	sec_ofs  = now.tv_sec  - date.tv_sec;
	usec_ofs = now.tv_usec - date.tv_usec;
	if ((int)usec_ofs < 0) {
		usec_ofs += 1000000;
		sec_ofs  -= 1;
	}
	ofs_new = ((ullong)sec_ofs << 32) + usec_ofs;
	if (ofs_new != ofs)
		HA_ATOMIC_STORE(&now_offset, ofs_new);
}

/* must be called once at boot to initialize some global variables */
void tv_init_process_date()
{
	now_offset = 0;
	gettimeofday(&date, NULL);
	now = after_poll = before_poll = date;
	global_now = ((ullong)date.tv_sec << 32) + (uint)date.tv_usec;
	global_now_ms = now.tv_sec * 1000 + now.tv_usec / 1000;
	ti->idle_pct = 100;
	tv_update_date(0, 1);
}

/* must be called once per thread to initialize their thread-local variables.
 * Note that other threads might also be initializing and running in parallel.
 */
void tv_init_thread_date()
{
	ullong old_now;

	gettimeofday(&date, NULL);
	after_poll = before_poll = date;

	old_now = _HA_ATOMIC_LOAD(&global_now);
	now.tv_sec = old_now >> 32;
	now.tv_usec = (uint)old_now;
	ti->idle_pct = 100;
	tv_update_date(0, 1);
}

/* returns the current date as returned by gettimeofday() in ISO+microsecond
 * format. It uses a thread-local static variable that the reader can consume
 * for as long as it wants until next call. Thus, do not call it from a signal
 * handler. If <pad> is non-0, a trailing space will be added. It will always
 * return exactly 32 or 33 characters (depending on padding) and will always be
 * zero-terminated, thus it will always fit into a 34 bytes buffer.
 * This also always include the local timezone (in +/-HH:mm format) .
 */
char *timeofday_as_iso_us(int pad)
{
	struct timeval new_date;
	struct tm tm;
	const char *offset;
	char c;
	gettimeofday(&new_date, NULL);
	if (new_date.tv_sec != iso_time_sec || !new_date.tv_sec) {
		get_localtime(new_date.tv_sec, &tm);
		offset = get_gmt_offset(new_date.tv_sec, &tm);
		if (unlikely(strftime(iso_time_str, sizeof(iso_time_str), "%Y-%m-%dT%H:%M:%S.000000+00:00", &tm) != 32))
			strcpy(iso_time_str, "YYYY-mm-ddTHH:MM:SS.000000-00:00"); // make the failure visible but respect format.
		iso_time_str[26] = offset[0];
		iso_time_str[27] = offset[1];
		iso_time_str[28] = offset[2];
		iso_time_str[30] = offset[3];
		iso_time_str[31] = offset[4];
		iso_time_sec = new_date.tv_sec;
	}
	/* utoa_pad adds a trailing 0 so we save the char for restore */
	c = iso_time_str[26];
	utoa_pad(new_date.tv_usec, iso_time_str + 20, 7);
	iso_time_str[26] = c;
	if (pad) {
		iso_time_str[32] = ' ';
		iso_time_str[33] = 0;
	}
	return iso_time_str;
}

/*
 * Local variables:
 *  c-indent-level: 8
 *  c-basic-offset: 8
 * End:
 */