plugins.d/loopsleepms.sh.inc

   1 # no need for shebang - this file is included from other scripts
   2
   3 LOOPSLEEP_DATE="$(which date)"
   4 if [ -z "$LOOPSLEEP_DATE" ]
   5     then
   6     echo >&2 "$0: ERROR: Cannot find the command 'date' in the system path."
   7     exit 1
   8 fi
   9
  10 # -----------------------------------------------------------------------------
  11 # use the date command as a high resolution timer
  12
  13 now_ms=
  14 LOOPSLEEPMS_HIGHRES=1
  15 test "$($LOOPSLEEP_DATE +%N)" = "%N" && LOOPSLEEPMS_HIGHRES=0
  16 current_time_ms_from_date() {
  17     if [ $LOOPSLEEPMS_HIGHRES -eq 0 ]
  18     then
  19         now_ms="$($LOOPSLEEP_DATE +'%s')000"
  20     else
  21         now_ms="$(( $( $LOOPSLEEP_DATE +'%s * 1000 + %-N / 1000000' ) ))"
  22     fi
  23 }
  24
  25 # -----------------------------------------------------------------------------
  26 # use /proc/uptime as a high resolution timer
  27
  28 current_time_ms_from_date
  29 current_time_ms_from_uptime_started="${now_ms}"
  30 current_time_ms_from_uptime_first=0
  31 current_time_ms_from_uptime() {
  32     local up rest arr n
  33
  34     read up rest </proc/uptime
  35     arr=(${up//./ })
  36
  37     if [ ${#arr[1]} -lt 1 ]
  38         then
  39         n="${arr[0]}000"
  40     elif [ ${#arr[1]} -lt 2 ]
  41         then
  42         n="${arr[0]}${arr[1]}00"
  43     elif [ ${#arr[1]} -lt 3 ]
  44         then
  45         n="${arr[0]}${arr[1]}0"
  46     else
  47         n="${arr[0]}${arr[1]}"
  48     fi
  49
  50     now_ms=$((current_time_ms_from_uptime_started - current_time_ms_from_uptime_first + n))
  51
  52     if [ "${now_ms}" -lt "${current_time_ms_from_uptime_started}" ]
  53         then
  54         echo >&2 "$0: Cannot use current_time_ms_from_uptime() - falling back to current_time_ms_from_date()."
  55         current_time_ms="current_time_ms_from_date"
  56         current_time_ms_from_date
  57         current_time_ms_accuracy=1
  58     fi
  59 }
  60 current_time_ms_from_uptime
  61 current_time_ms_from_uptime_first="$((now_ms - current_time_ms_from_uptime_started))"
  62 current_time_ms="current_time_ms_from_uptime"
  63 current_time_ms_accuracy=10
  64 if [ "${current_time_ms_from_uptime_first}" -eq 0 ]
  65     then
  66     echo >&2 "$0: Invalid setup for current_time_ms_from_uptime() - falling back to current_time_ms_from_date()."
  67     current_time_ms="current_time_ms_from_date"
  68     current_time_ms_accuracy=1
  69 fi
  70
  71 # -----------------------------------------------------------------------------
  72 # use read with timeout for sleep
  73
  74 mysleep="mysleep_read"
  75
  76 mysleep_fifo="${NETDATA_CACHE_DIR-/tmp}/.netdata_bash_sleep_timer_fifo"
  77 [ -e "${mysleep_fifo}" ] && rm "${mysleep_fifo}"
  78 mkfifo "${mysleep_fifo}" || mysleep="sleep"
  79
  80 mysleep_read() {
  81     read -t "${1}" <>"${mysleep_fifo}"
  82     ret=$?
  83     if [ $ret -le 128 ]
  84         then
  85         echo >&2 "$0: Cannot use read for sleeping (return code ${ret})."
  86         mysleep="sleep"
  87         ${mysleep} "${1}"
  88     fi
  89 }
  90
  91
  92 # -----------------------------------------------------------------------------
  93 # this function is used to sleep a fraction of a second
  94 # it calculates the difference between every time is called
  95 # and tries to align the sleep time to give you exactly the
  96 # loop you need.
  97
  98 LOOPSLEEPMS_LASTRUN=0
  99 LOOPSLEEPMS_LASTSLEEP=0
 100 LOOPSLEEPMS_LASTWORK=0
 101
 102 loopsleepms() {
 103     local tellwork=0 t="$1" div s m now mstosleep
 104
 105     if [ "$t" = "tellwork" ]
 106     then
 107         tellwork=1
 108         shift
 109         t="$1"
 110     fi
 111     div="${2-100}"
 112
 113     # $t = the time in seconds to wait
 114
 115     # if high resolution is not supported
 116     # just sleep the time requested, in seconds
 117     if [ $LOOPSLEEPMS_HIGHRES -eq 0 ]
 118     then
 119         sleep $t
 120         return
 121     fi
 122
 123     # get the current time, in ms
 124     # milliseconds since epoch (1-1-1970)
 125     now="$(( $( $LOOPSLEEP_DATE +'%s * 1000 + %-N / 1000000' ) ))"
 126
 127     # calculate required sleep in ms
 128     t=$((t * 1000 * div / 100))
 129
 130     # this is our first run
 131     # just wait the requested time
 132     test $LOOPSLEEPMS_LASTRUN -eq 0 && LOOPSLEEPMS_LASTRUN=$now
 133
 134     # calculate ms since last run
 135     LOOPSLEEPMS_LASTWORK=$((now - LOOPSLEEPMS_LASTRUN - LOOPSLEEPMS_LASTSLEEP))
 136     # echo "# last loop's work took $LOOPSLEEPMS_LASTWORK ms"
 137
 138     # calculate ms to sleep
 139     mstosleep=$(( t - LOOPSLEEPMS_LASTWORK + current_time_ms_accuracy ))
 140     # echo "# mstosleep is $mstosleep ms"
 141
 142     # if we are too slow, sleep some time
 143     test $mstosleep -lt 200 && mstosleep=200
 144
 145     s=$((mstosleep / 1000))
 146     m=$((mstosleep - (s * 1000)))
 147
 148     test $tellwork -eq 1 && echo >&2 " >>> PERFORMANCE >>> WORK TOOK $LOOPSLEEPMS_LASTWORK ms ( $((LOOPSLEEPMS_LASTWORK * 100 / 1000)).$((LOOPSLEEPMS_LASTWORK % 10))% cpu ) >>> SLEEPING $mstosleep ms"
 149
 150     # echo "# sleeping $s.$m"
 151     # echo
 152     ${mysleep} $s.$m
 153
 154     # keep the values we need
 155     # for our next run
 156     LOOPSLEEPMS_LASTRUN=$now
 157     LOOPSLEEPMS_LASTSLEEP=$mstosleep
 158 }