utils/collectd/patches/500-fix-uptime-reading.patch

   1 From af01dd6fa3eb458e2fbb272703b0cae37ea54a9b Mon Sep 17 00:00:00 2001
   2 From: Marcin Jurkowski <marcin1j@gmail.com>
   3 Date: Tue, 11 Jul 2017 15:00:25 +0200
   4 Subject: [PATCH] uptime plugin: don't cache boot time and simplify Linux code
   5
   6 Caching boottime on startup yields incorrect uptime values if system
   7 date changes after the daemon is started.
   8 This is almost certain to happen on embedded systems without RTC, where
   9 clock is set from NTP server at some point after boot process.
  10
  11 On Linux, we can retrieve uptime directly by either reading /proc/uptime
  12 (it's sufficient to read a few bytes) or calling sysinfo() function.
  13 Use the latter since it's the most efficient way in speed, memory
  14 requirements and code simplicity terms.
  15 ---
  16  src/uptime.c | 71 ++++++++++++++++--------------------------------------------
  17  1 file changed, 19 insertions(+), 52 deletions(-)
  18
  19 --- a/src/uptime.c
  20 +++ b/src/uptime.c
  21 @@ -25,8 +25,7 @@
  22  #include "plugin.h"
  23
  24  #if KERNEL_LINUX
  25 -#define STAT_FILE "/proc/stat"
  26 -/* Using /proc filesystem to retrieve the boot time, Linux only. */
  27 +#include <sys/sysinfo.h>
  28  /* #endif KERNEL_LINUX */
  29
  30  #elif HAVE_LIBKSTAT
  31 @@ -53,8 +52,6 @@
  32  /*
  33   * Global variables
  34   */
  35 -/* boottime always used, no OS distinction */
  36 -static time_t boottime;
  37
  38  #if HAVE_LIBKSTAT
  39  extern kstat_ctl_t *kc;
  40 @@ -72,8 +69,6 @@ static void uptime_submit(gauge_t value)
  41    plugin_dispatch_values(&vl);
  42  }
  43
  44 -static int uptime_init(void) /* {{{ */
  45 -{
  46  /*
  47   * On most unix systems the uptime is calculated by looking at the boot
  48   * time (stored in unix time, since epoch) and the current one. We are
  49 @@ -84,48 +79,21 @@ static int uptime_init(void) /* {{{ */
  50   * the boot time, the plugin is unregistered and there is no chance to
  51   * try again later. Nevertheless, this is very unlikely to happen.
  52   */
  53 -
  54 +static time_t uptime_get_sys(void) { /* {{{ */
  55 +  time_t result;
  56  #if KERNEL_LINUX
  57 -  unsigned long starttime;
  58 -  char buffer[1024];
  59 -  int ret;
  60 -  FILE *fh;
  61 -
  62 -  ret = 0;
  63 -
  64 -  fh = fopen(STAT_FILE, "r");
  65 +  struct sysinfo info;
  66 +  int status;
  67
  68 -  if (fh == NULL) {
  69 +  status = sysinfo(&info);
  70 +  if (status != 0) {
  71      char errbuf[1024];
  72 -    ERROR("uptime plugin: Cannot open " STAT_FILE ": %s",
  73 +    ERROR("uptime plugin: Error calling sysinfo: %s",
  74            sstrerror(errno, errbuf, sizeof(errbuf)));
  75      return (-1);
  76    }
  77
  78 -  while (fgets(buffer, 1024, fh) != NULL) {
  79 -    /* look for the btime string and read the value */
  80 -    ret = sscanf(buffer, "btime %lu", &starttime);
  81 -    /* avoid further loops if btime has been found and read
  82 -     * correctly (hopefully) */
  83 -    if (ret == 1)
  84 -      break;
  85 -  }
  86 -
  87 -  fclose(fh);
  88 -
  89 -  /* loop done, check if no value has been found/read */
  90 -  if (ret != 1) {
  91 -    ERROR("uptime plugin: No value read from " STAT_FILE "");
  92 -    return (-1);
  93 -  }
  94 -
  95 -  boottime = (time_t)starttime;
  96 -
  97 -  if (boottime == 0) {
  98 -    ERROR("uptime plugin: btime read from " STAT_FILE ", "
  99 -          "but `boottime' is zero!");
 100 -    return (-1);
 101 -  }
 102 +  result = (time_t)info.uptime;
 103  /* #endif KERNEL_LINUX */
 104
 105  #elif HAVE_LIBKSTAT
 106 @@ -159,13 +127,13 @@ static int uptime_init(void) /* {{{ */
 107      return (-1);
 108    }
 109
 110 -  boottime = (time_t)knp->value.ui32;
 111 -
 112 -  if (boottime == 0) {
 113 +  if (knp->value.ui32 == 0) {
 114      ERROR("uptime plugin: kstat_data_lookup returned success, "
 115            "but `boottime' is zero!");
 116      return (-1);
 117    }
 118 +
 119 +  result = time(NULL) - (time_t)knp->value.ui32;
 120  /* #endif HAVE_LIBKSTAT */
 121
 122  #elif HAVE_SYS_SYSCTL_H
 123 @@ -186,13 +154,13 @@ static int uptime_init(void) /* {{{ */
 124      return (-1);
 125    }
 126
 127 -  boottime = boottv.tv_sec;
 128 -
 129 -  if (boottime == 0) {
 130 +  if (boottv.tv_sec == 0) {
 131      ERROR("uptime plugin: sysctl(3) returned success, "
 132            "but `boottime' is zero!");
 133      return (-1);
 134    }
 135 +
 136 +  result = time(NULL) - boottv.tv_sec;
 137  /* #endif HAVE_SYS_SYSCTL_H */
 138
 139  #elif HAVE_PERFSTAT
 140 @@ -212,18 +180,18 @@ static int uptime_init(void) /* {{{ */
 141    if (hertz <= 0)
 142      hertz = HZ;
 143
 144 -  boottime = time(NULL) - cputotal.lbolt / hertz;
 145 +  result = cputotal.lbolt / hertz;
 146  #endif /* HAVE_PERFSTAT */
 147
 148 -  return (0);
 149 -} /* }}} int uptime_init */
 150 +  return result;
 151 +} /* }}} int uptime_get_sys */
 152
 153  static int uptime_read(void) {
 154    gauge_t uptime;
 155    time_t elapsed;
 156
 157    /* calculate the amount of time elapsed since boot, AKA uptime */
 158 -  elapsed = time(NULL) - boottime;
 159 +  elapsed = uptime_get_sys();
 160
 161    uptime = (gauge_t)elapsed;
 162
 163 @@ -233,6 +201,5 @@ static int uptime_read(void) {
 164  }
 165
 166  void module_register(void) {
 167 -  plugin_register_init("uptime", uptime_init);
 168    plugin_register_read("uptime", uptime_read);
 169  } /* void module_register */