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In pgbench logging, avoid assuming that instr_times match Unix timestamps.

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For aggregated logging, pg_bench supposed that printing the integer part of
INSTR_TIME_GET_DOUBLE() would produce a Unix timestamp.  That was already
broken on Windows, and it's about to get broken on most other platforms as
well.  As in commit 74baa1e3b, we can remove the entanglement at the price
of one extra syscall per transaction; though here it seems more convenient
to use time(NULL) instead of gettimeofday(), since we only need
integral-second precision.

I took the time to do some wordsmithing on the documentation about
pgbench's logging features, too.

Discussion: https://postgr.es/m/8837.1483216839@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2017-01-02 12:26:03 -05:00
parent 74baa1e3b8
commit 67a875355e
2 changed files with 84 additions and 74 deletions
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62
src/bin/pgbench/pgbench.c
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@ -42,6 +42,7 @@
#include <limits.h>
#include <math.h>
#include <signal.h>
#include <time.h>
#include <sys/time.h>
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
@ -227,7 +228,7 @@ typedef struct SimpleStats
*/
typedef struct StatsData
{
long start_time; /* interval start time, for aggregates */
time_t start_time; /* interval start time, for aggregates */
int64 cnt; /* number of transactions */
int64 skipped; /* number of transactions skipped under --rate
* and --latency-limit */
@ -449,7 +450,7 @@ static const BuiltinScript builtin_script[] =
static void setIntValue(PgBenchValue *pv, int64 ival);
static void setDoubleValue(PgBenchValue *pv, double dval);
static bool evaluateExpr(TState *, CState *, PgBenchExpr *, PgBenchValue *);
static void doLog(TState *thread, CState *st, instr_time *now,
static void doLog(TState *thread, CState *st,
StatsData *agg, bool skipped, double latency, double lag);
static void processXactStats(TState *thread, CState *st, instr_time *now,
bool skipped, StatsData *agg);
@ -780,7 +781,7 @@ mergeSimpleStats(SimpleStats *acc, SimpleStats *ss)
* the given value.
*/
static void
initStats(StatsData *sd, double start_time)
initStats(StatsData *sd, time_t start_time)
{
sd->start_time = start_time;
sd->cnt = 0;
@ -2425,10 +2426,15 @@ doCustom(TState *thread, CState *st, StatsData *agg)
}
/*
* print log entry after completing one transaction.
* Print log entry after completing one transaction.
*
* We print Unix-epoch timestamps in the log, so that entries can be
* correlated against other logs. On some platforms this could be obtained
* from the instr_time reading the caller has, but rather than get entangled
* with that, we just eat the cost of an extra syscall in all cases.
*/
static void
doLog(TState *thread, CState *st, instr_time *now,
doLog(TState *thread, CState *st,
StatsData *agg, bool skipped, double latency, double lag)
{
FILE *logfile = thread->logfile;
@ -2447,15 +2453,17 @@ doLog(TState *thread, CState *st, instr_time *now,
if (agg_interval > 0)
{
/*
* Loop until we reach the interval of the current transaction, and
* print all the empty intervals in between (this may happen with very
* low tps, e.g. --rate=0.1).
* Loop until we reach the interval of the current moment, and print
* any empty intervals in between (this may happen with very low tps,
* e.g. --rate=0.1).
*/
while (agg->start_time + agg_interval < INSTR_TIME_GET_DOUBLE(*now))
time_t now = time(NULL);
while (agg->start_time + agg_interval <= now)
{
/* print aggregated report to logfile */
fprintf(logfile, "%ld " INT64_FORMAT " %.0f %.0f %.0f %.0f",
agg->start_time,
(long) agg->start_time,
agg->cnt,
agg->latency.sum,
agg->latency.sum2,
@ -2485,12 +2493,6 @@ doLog(TState *thread, CState *st, instr_time *now,
/* no, print raw transactions */
struct timeval tv;
/*
* We print the current system timestamp in the log, so that entries
* can be correlated against other logs. On some platforms this is
* available in *now, but rather than get entangled with that, we just
* eat the cost of an extra syscall in all cases.
*/
gettimeofday(&tv, NULL);
if (skipped)
fprintf(logfile, "%d " INT64_FORMAT " skipped %d %ld %ld",
@ -2518,7 +2520,7 @@ processXactStats(TState *thread, CState *st, instr_time *now,
double latency = 0.0,
lag = 0.0;
if ((!skipped || agg_interval) && INSTR_TIME_IS_ZERO(*now))
if ((!skipped) && INSTR_TIME_IS_ZERO(*now))
INSTR_TIME_SET_CURRENT(*now);
if (!skipped)
@ -2540,7 +2542,7 @@ processXactStats(TState *thread, CState *st, instr_time *now,
thread->stats.cnt++;
if (use_log)
doLog(thread, st, now, agg, skipped, latency, lag);
doLog(thread, st, agg, skipped, latency, lag);
/* XXX could use a mutex here, but we choose not to */
if (per_script_stats)
@ -3202,7 +3204,7 @@ ParseScript(const char *script, const char *desc, int weight)
ps.desc = desc;
ps.weight = weight;
ps.commands = (Command **) pg_malloc(sizeof(Command *) * alloc_num);
initStats(&ps.stats, 0.0);
initStats(&ps.stats, 0);
/* Prepare to parse script */
sstate = psql_scan_create(&pgbench_callbacks);
@ -3972,10 +3974,6 @@ main(int argc, char **argv)
}
break;
case 5:
#ifdef WIN32
fprintf(stderr, "--aggregate-interval is not currently supported on Windows\n");
exit(1);
#else
benchmarking_option_set = true;
agg_interval = atoi(optarg);
if (agg_interval <= 0)
@ -3984,7 +3982,6 @@ main(int argc, char **argv)
optarg);
exit(1);
}
#endif
break;
case 6:
progress_timestamp = true;
@ -4267,7 +4264,7 @@ main(int argc, char **argv)
thread->random_state[2] = random();
thread->logfile = NULL; /* filled in later */
thread->latency_late = 0;
initStats(&thread->stats, 0.0);
initStats(&thread->stats, 0);
nclients_dealt += thread->nstate;
}
@ -4321,7 +4318,7 @@ main(int argc, char **argv)
#endif /* ENABLE_THREAD_SAFETY */
/* wait for threads and accumulate results */
initStats(&stats, 0.0);
initStats(&stats, 0);
INSTR_TIME_SET_ZERO(conn_total_time);
for (i = 0; i < nthreads; i++)
{
@ -4394,6 +4391,9 @@ threadRun(void *arg)
INSTR_TIME_SET_ZERO(thread->conn_time);
initStats(&aggs, time(NULL));
last = aggs;
/* open log file if requested */
if (use_log)
{
@ -4429,9 +4429,6 @@ threadRun(void *arg)
INSTR_TIME_SET_CURRENT(thread->conn_time);
INSTR_TIME_SUBTRACT(thread->conn_time, thread->start_time);
initStats(&aggs, INSTR_TIME_GET_DOUBLE(thread->start_time));
last = aggs;
/* explicitly initialize the state machines */
for (i = 0; i < nstate; i++)
{
@ -4635,7 +4632,7 @@ threadRun(void *arg)
* (If a read from a 64-bit integer is not atomic, you might
* get a "torn" read and completely bogus latencies though!)
*/
initStats(&cur, 0.0);
initStats(&cur, 0);
for (i = 0; i < nthreads; i++)
{
mergeSimpleStats(&cur.latency, &thread[i].stats.latency);
@ -4695,12 +4692,13 @@ done:
INSTR_TIME_ACCUM_DIFF(thread->conn_time, end, start);
if (thread->logfile)
{
if (agg_interval)
if (agg_interval > 0)
{
/* log aggregated but not yet reported transactions */
doLog(thread, state, &end, &aggs, false, 0, 0);
doLog(thread, state, &aggs, false, 0, 0);
}
fclose(thread->logfile);
thread->logfile = NULL;
}
return NULL;
}