parallel.sh

#!/bin/bash
# Call a script in a tight loop from multiple processes.
# Run as `$0 master <#seconds> <#children> script-and-args...`.
# seconds and children control run length and concurrency

# Modes:
# master <seconds> <children>: Fork and run n child processes for m seconds
# child: Call on tight loop, indefinitely
# test: Call just once

myself="$0"
mode="$1"
shift

if [[ "$mode" = 'master' ]]; then
  # Volume properties
  seconds="$1"
  shift
  children="$1"
  shift
fi

scriptAndArgs=( "$@" )

function do_call {
  "${scriptAndArgs[@]}"
}

function emit_call {
  echo `date -u +"%Y%m%d.%H%M%SZ"`$'\t'"`do_call`"
}

function run_indefinitely {
  while true; do
    emit_call
  done
}

if [[ "$mode" = 'master' ]]; then
  for (( child_id=0; child_id < $children; child_id++ )); do
    timeout "${seconds}s" "$myself" child "${scriptAndArgs[@]}" &
  done
  wait
elif [[ "$mode" = 'child' ]]; then
  run_indefinitely
elif [[ "$mode" = 'test' ]]; then
  emit_call # just run once
else
  echo "Bad mode"
  exit 2
fi