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     if [ $? -ne 0 ]
  36         then
  37         echo >&2 "$0: Cannot read /proc/uptime - falling back to current_time_ms_from_date()."
  38         current_time_ms="current_time_ms_from_date"
  39         current_time_ms_from_date
  40         current_time_ms_accuracy=1
  41         return
  42     fi
  43
  44     arr=(${up//./ })
  45
  46     if [ ${#arr[1]} -lt 1 ]
  47         then
  48         n="${arr[0]}000"
  49     elif [ ${#arr[1]} -lt 2 ]
  50         then
  51         n="${arr[0]}${arr[1]}00"
  52     elif [ ${#arr[1]} -lt 3 ]
  53         then
  54         n="${arr[0]}${arr[1]}0"
  55     else
  56         n="${arr[0]}${arr[1]}"
  57     fi
  58
  59     now_ms=$((current_time_ms_from_uptime_started - current_time_ms_from_uptime_first + n))
  60
  61     if [ "${now_ms}" -lt "${current_time_ms_from_uptime_started}" ]
  62         then
  63         echo >&2 "$0: Cannot use current_time_ms_from_uptime() - falling back to current_time_ms_from_date()."
  64         current_time_ms="current_time_ms_from_date"
  65         current_time_ms_from_date
  66         current_time_ms_accuracy=1
  67     fi
  68 }
  69 current_time_ms_from_uptime
  70 current_time_ms_from_uptime_first="$((now_ms - current_time_ms_from_uptime_started))"
  71 current_time_ms="current_time_ms_from_uptime"
  72 current_time_ms_accuracy=10
  73 if [ "${current_time_ms_from_uptime_first}" -eq 0 ]
  74     then
  75     echo >&2 "$0: Invalid setup for current_time_ms_from_uptime() - falling back to current_time_ms_from_date()."
  76     current_time_ms="current_time_ms_from_date"
  77     current_time_ms_accuracy=1
  78 fi
  79
  80 # -----------------------------------------------------------------------------
  81 # use read with timeout for sleep
  82
  83 mysleep="mysleep_read"
  84
  85 mysleep_fifo="${NETDATA_CACHE_DIR-/tmp}/.netdata_bash_sleep_timer_fifo"
  86 [ ! -e "${mysleep_fifo}" ] && mkfifo "${mysleep_fifo}"
  87 [ ! -e "${mysleep_fifo}" ] && mysleep="sleep"
  88
  89 mysleep_read() {
  90     read -t "${1}" <>"${mysleep_fifo}"
  91     ret=$?
  92     if [ $ret -le 128 ]
  93         then
  94         echo >&2 "$0: Cannot use read for sleeping (return code ${ret})."
  95         mysleep="sleep"
  96         ${mysleep} "${1}"
  97     fi
  98 }
  99
 100
 101 # -----------------------------------------------------------------------------
 102 # this function is used to sleep a fraction of a second
 103 # it calculates the difference between every time is called
 104 # and tries to align the sleep time to give you exactly the
 105 # loop you need.
 106
 107 LOOPSLEEPMS_LASTRUN=0
 108 LOOPSLEEPMS_NEXTRUN=0
 109 LOOPSLEEPMS_LASTSLEEP=0
 110 LOOPSLEEPMS_LASTWORK=0
 111
 112 loopsleepms() {
 113     local tellwork=0 t="${1}" div s m now mstosleep
 114
 115     if [ "${t}" = "tellwork" ]
 116     then
 117         tellwork=1
 118         shift
 119         t="${1}"
 120     fi
 121
 122     # $t = the time in seconds to wait
 123
 124     # if high resolution is not supported
 125     # just sleep the time requested, in seconds
 126     if [ ${LOOPSLEEPMS_HIGHRES} -eq 0 ]
 127     then
 128         sleep ${t}
 129         return
 130     fi
 131
 132     # get the current time, in ms
 133     ${current_time_ms}
 134
 135     # this is our first run
 136     # just wait the requested time
 137     if [ ${LOOPSLEEPMS_LASTRUN} -eq 0 ]
 138         then
 139         LOOPSLEEPMS_LASTWORK=0
 140     else
 141         # calculate ms since last run
 142         LOOPSLEEPMS_LASTWORK=$((now_ms - LOOPSLEEPMS_LASTRUN - LOOPSLEEPMS_LASTSLEEP))
 143     fi
 144     # echo "# last loop's work took $LOOPSLEEPMS_LASTWORK ms"
 145
 146     # remember this run
 147     LOOPSLEEPMS_LASTRUN=${now_ms}
 148
 149     # calculate the next run
 150     LOOPSLEEPMS_NEXTRUN=$(( ( now_ms - now_ms % ( t * 1000 ) ) + ( t * 1000 ) ))
 151
 152     # calculate ms to sleep
 153     mstosleep=$(( LOOPSLEEPMS_NEXTRUN - now_ms + current_time_ms_accuracy ))
 154     # echo "# mstosleep is $mstosleep ms"
 155
 156     # if we are too slow, sleep some time
 157     test ${mstosleep} -lt 200 && mstosleep=200
 158
 159     s=$((mstosleep / 1000))
 160     m=$((mstosleep - (s * 1000)))
 161
 162     test $tellwork -eq 1 && echo >&2 " >>> PERFORMANCE >>> WORK TOOK ${LOOPSLEEPMS_LASTWORK} ms ( $((LOOPSLEEPMS_LASTWORK * 100 / 1000)).$((LOOPSLEEPMS_LASTWORK % 10))% cpu ) >>> SLEEPING ${mstosleep} ms"
 163
 164     # echo "# sleeping ${s}.${m}"
 165     # echo
 166     ${mysleep} ${s}.${m}
 167
 168     # keep the values we need
 169     # for our next run
 170     LOOPSLEEPMS_LASTSLEEP=$mstosleep
 171 }
 172