user-tools/pvalve

   1 #!/bin/bash
   2
   3 true <<EOF
   4
   5 =pod
   6
   7 =head1 NAME
   8
   9 pvalve - Control how much a given command should run by an other command's exit code
  10
  11 =head1 SYNOPSIS
  12
  13 pvalve [<B<CONTROL COMMAND>>] -- [<B<LONG RUNNING COMMAND>>]
  14
  15 Controls when B<LONG RUNNING COMMAND> should run, by pause and unpause it
  16 according to the B<CONTROL COMMAND>'s exit status.
  17
  18 =head1 DESCRIPTION
  19
  20 Pause B<LONG RUNNING COMMAND> process group with STOP signal(7) if B<CONTROL COMMAND> exits non-zero.
  21 Unpause B<LONG RUNNING COMMAND> process group with CONT signal(7) if B<CONTROL COMMAND> exits zero.
  22
  23 Pvalve takes the last line from B<CONTROL COMMAND>'s stdout, and if looks like a time interval
  24 (ie. positive number with optional fraction followed by optional "s", "m", or "h" suffix)
  25 then the next checking of B<CONTROL COMMAND> will start after that much time.
  26 Otherwise it takes B<PVALVE_INTERVAL> environment variable,
  27 or start next check immediately if it's not set.
  28
  29 Pvalve won't bombard B<LONG RUNNING COMMAND> with more consecutive STOP or CONT signals.
  30
  31 =head1 USEFULNESS
  32
  33 It's useful eg. for basic load control. Start a CPU-intensive program in B<LONG RUNNING COMMAND>
  34 and check hardware temperature in B<CONTROL COMMAND>. Make it exit 0 when temperature is below
  35 a certain value, and exit 1 if above an other, higher value.
  36
  37 =head1 ENVIRONMENT
  38
  39 =over 4
  40
  41 =item B<PVALVE_INTERVAL>
  42
  43 Default interval between two B<CONTROL COMMAND> runs.
  44
  45 =item B<PVALVE_STATUS>
  46
  47 B<PVALVE_STATUS> describes whether B<LONG RUNNING COMMAND> should be in running or in paused state.
  48 Possible values: RUN, STOP.
  49 This environment is available by B<CONTROL COMMAND>.
  50
  51 =item B<PVALVE_PID>
  52
  53 PID of B<LONG RUNNING COMMAND>.
  54
  55 =back
  56
  57 =head1 CAVEATS
  58
  59 Further process groups which are created by B<LONG RUNNING COMMAND> will not be affected.
  60
  61 =cut
  62
  63 EOF
  64
  65
  66
  67 toolname=pvalve
  68 declare -a controller_cmd
  69 declare -a controlled_cmd
  70
  71 while [ $# -gt 0 ]
  72 do
  73         case "$1" in
  74         --help|-h)
  75                 pod2text "$0"
  76                 exit
  77                 ;;
  78         esac
  79
  80         if [ "$1" = -- ]
  81         then
  82                 shift
  83                 break
  84         fi
  85         controller_cmd+=("$1")
  86         shift
  87 done
  88
  89 while [ $# -gt 0 ]
  90 do
  91         controlled_cmd+=("$1")
  92         shift
  93 done
  94
  95 quit()
  96 {
  97         kill -TERM -$PVALVE_PID
  98         if [ "$PVALVE_STATUS" = STOP ]
  99         then
 100                 kill -CONT -$PVALVE_PID
 101         fi
 102         exit 130
 103 }
 104
 105 exists()
 106 {
 107         local pid=$1
 108         declare -g ancestor_valid
 109         if [ "$ancestor_valid" != no ]
 110         then
 111                 kill -0 $pid 2>/dev/null && return 0 || ancestor_valid=no
 112         fi
 113         kill -0 -$pid 2>/dev/null
 114 }
 115
 116
 117 trap quit TERM INT
 118
 119 setpgrp "${controlled_cmd[@]}" &
 120 PVALVE_PID=$!
 121 export PVALVE_PID
 122 PVALVE_STATUS=RUN
 123 export PVALVE_STATUS
 124
 125 echo "$toolname: RUN $PVALVE_PID" >&2
 126
 127 stdout_file=`readlink /proc/self/fd/1`
 128 exec {stdout_copy_fd}> "$stdout_file"
 129
 130 while exists $PVALVE_PID
 131 do
 132         delay=`command "${controller_cmd[@]}" | tee /dev/fd/$stdout_copy_fd | tail -n1; exit ${PIPESTATUS[0]}`
 133         code=$?
 134
 135         if [ $code = 0 -a $PVALVE_STATUS != RUN ]
 136         then
 137                 echo "$toolname: CONT -$PVALVE_PID" >&2
 138                 kill -CONT -$PVALVE_PID
 139                 PVALVE_STATUS=RUN
 140         elif [ $code != 0 -a $PVALVE_STATUS = RUN ]
 141         then
 142                 echo "$toolname: STOP -$PVALVE_PID" >&2
 143                 kill -STOP -$PVALVE_PID
 144                 PVALVE_STATUS=STOP
 145         fi
 146
 147         if [[ $delay =~ ^[0-9]+([.,][0-9]+)?[smh]?$ ]]
 148         then
 149                 true
 150         else
 151                 delay=${PVALVE_INTERVAL:-0}
 152         fi
 153
 154         echo "$toolname: next check in $delay sec" >&2
 155         sleep $delay
 156 done
 157
 158 wait