BUG/MINOR: clock: do not mix wall-clock and monotonic time in uptime calculation
We've had a start date even before the internal monotonic clock existed,
but once the monotonic clock was added, the start date was not updated
to distinguish the wall clock time units and the internal monotonic time
units. The distinction is important because both clocks do not necessarily
progress at the same speed. The very rare occurrences of the wall-clock
date are essentially for human consumption and communication with third
parties (e.g. report the start date in "show info" for monitoring
purposes). However currently this one is also used to measure the distance
to "now" as being the process' uptime. This is actually not correct. It
only works because for now the two dates are initialized at the exact
same instant at boot but could still be wrong if the system's date shows
a big jump backwards during startup for example. In addition the current
situation prevents us from enforcing an abritrary offset at boot to reveal
some heisenbugs.
This patch adds a new "start_time" at boot that is set from "now" and is
used in uptime calculations. "start_date" instead is now set from "date"
and will always reflect the system date for human consumption (e.g. in
"show info"). This way we're now sure that any drift of the internal
clock relative to the system date will not impact the reported uptime.
This could possibly be backported though it's unlikely that anyone has
ever noticed the problem.
diff --git a/include/haproxy/clock.h b/include/haproxy/clock.h
index 22bb2c9..a6f7cd2 100644
--- a/include/haproxy/clock.h
+++ b/include/haproxy/clock.h
@@ -26,6 +26,7 @@
#include <haproxy/api.h>
extern struct timeval start_date; /* the process's start date in wall-clock time */
+extern struct timeval start_time; /* the process's start date in internal monotonic time */
extern volatile ullong global_now; /* common monotonic date between all threads (32:32) */
extern THREAD_LOCAL struct timeval now; /* internal monotonic date derived from real clock */
diff --git a/src/activity.c b/src/activity.c
index 5ee5fbb..010fd31 100644
--- a/src/activity.c
+++ b/src/activity.c
@@ -1083,7 +1083,7 @@
} while (0)
/* retrieve uptime */
- tv_remain(&start_date, &now, &up);
+ tv_remain(&start_time, &now, &up);
chunk_appendf(&trash, "thread_id: %u (%u..%u)\n", tid + 1, 1, global.nbthread);
chunk_appendf(&trash, "date_now: %lu.%06lu\n", (ulong)now.tv_sec, (ulong)now.tv_usec);
diff --git a/src/clock.c b/src/clock.c
index 3d96c31..75d2293 100644
--- a/src/clock.c
+++ b/src/clock.c
@@ -27,6 +27,7 @@
#include <haproxy/tools.h>
struct timeval start_date; /* the process's start date in wall-clock time */
+struct timeval start_time; /* the process's start date in internal monotonic time */
volatile ullong global_now; /* common monotonic date between all threads (32:32) */
volatile uint global_now_ms; /* common monotonic date in milliseconds (may wrap) */
diff --git a/src/haproxy.c b/src/haproxy.c
index e03b238..f7e0b34 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -1504,7 +1504,8 @@
/* initialize date, time, and pid */
tzset();
clock_init_process_date();
- start_date = now;
+ start_date = date;
+ start_time = now;
pid = getpid();
/* Set local host name and adjust some environment variables.
diff --git a/src/stats.c b/src/stats.c
index 960fcbf..9866a54 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -4613,7 +4613,7 @@
}
glob_out_b32 *= 32; // values are 32-byte units
- tv_remain(&start_date, &now, &up);
+ tv_remain(&start_time, &now, &up);
if (len < INF_TOTAL_FIELDS)
return 0;
@@ -4635,7 +4635,7 @@
chunk_appendf(out, "%ud %uh%02um%02us", (uint)up.tv_sec / 86400, ((uint)up.tv_sec % 86400) / 3600, ((uint)up.tv_sec % 3600) / 60, ((uint)up.tv_sec % 60));
info[INF_UPTIME_SEC] = (flags & STAT_USE_FLOAT) ? mkf_flt(FN_DURATION, up.tv_sec + up.tv_usec / 1000000.0) : mkf_u32(FN_DURATION, up.tv_sec);
- info[INF_START_TIME_SEC] = (flags & STAT_USE_FLOAT) ? mkf_flt(FN_DURATION, start_date.tv_sec + start_date.tv_usec / 1000000.0) : mkf_u32(FN_DURATION, start_date.tv_sec);
+ info[INF_START_TIME_SEC] = (flags & STAT_USE_FLOAT) ? mkf_flt(FN_DURATION, start_time.tv_sec + start_time.tv_usec / 1000000.0) : mkf_u32(FN_DURATION, start_time.tv_sec);
info[INF_MEMMAX_MB] = mkf_u32(FO_CONFIG|FN_LIMIT, global.rlimit_memmax);
info[INF_MEMMAX_BYTES] = mkf_u32(FO_CONFIG|FN_LIMIT, global.rlimit_memmax * 1048576L);
info[INF_POOL_ALLOC_MB] = mkf_u32(0, (unsigned)(pool_total_allocated() / 1048576L));