cronwrap.lockf

#!/bin/sh

# usage: cronwrap name interval command...
# jon@zomo.co.uk. See README for blurbs.

# cronwrap runs the specified command under lockf's protection
# output is placed in a timestamped file under ${LOG_DIR}/${NAME}
# this directory contains some extra goodies too:
#
# interval isn't used other than to write it into the log
# monitoring systems may use it to detect overdue jobs
#
#   last_run       symlink to last log
#   last_job_ok    symlink to log of last successful execution of the job
#   last_job_fail  symlink to log of last failed execution
#   last_lock_fail symlink to log of last locked execution
#
# it also contains a subdirectory 'status', which contains:
#
#   OK / FAIL / LOCK marker indicating status of last exiting run (*)
#   job_ok           list of timestamps when the job ran ok
#   job_fail         list of timestamps when the job failed
#   lock_fail        list of timestamps when the job was locked
#
# (*) note that this may not be the last run that is invoked by cron, which may
#     have been declined by lockf. this locked attempt will create the LOCK marker,
#     but if the first job eventually succeeds it will replace it the OK marker.
#
# override CRONWRAP_LOG_DIR, CRONWRAP_LOCK_DIR, CRONWRAP_LOCK_NAME as appropriate
#
# caution: don't place CRONWRAP_LOCK_DIR on a shared filesystem, they tend to have
#          different locking behaviours

# -d logdir
# -l lockdir
# -n lockname
usage() {
   echo 'usage: cronwrap [ options ] name interval command' >&2
   echo >&2
   # shellcheck disable=2016
   echo '  -d cronwrap_log_dir   (or set CRONWRAP_LOG_DIR)    default: /var/log/cronwrap/${name}' >&2
   # shellcheck disable=2016
   echo '  -l cronwrap_lock_dir  (or set CRONWRAP_LOCK_DIR)   default: /var/log/cronwrap/${name}' >&2
   # shellcheck disable=2016
   echo '  -n cronwrap_lock_name (or set CRONWRAP_LOCK_NAME)  default: ${name}'                   >&2
   echo '  -q                    (or set CRONWRAP_QUIET_LOCK) record locked jobs with status OK'  >&2
   echo >&2
   # shellcheck disable=2016
   echo 'lockfile is ${cronwrap_lock_dir}/${cronwrap_lock_name}.lock'                             >&2
   exit 1
 }

while getopts ":d:l:n:q" opt ; do
  case ${opt} in
    d)  CRONWRAP_LOG_DIR=${OPTARG}   ;;
    l)  CRONWRAP_LOCK_DIR=${OPTARG}  ;;
    n)  CRONWRAP_LOCK_NAME=${OPTARG} ;;
    q)  CRONWRAP_QUIET_LOCK=1        ;;
    \?) usage ;;
  esac
done
shift $((OPTIND -1))

NAME=$1 ; shift
INT=$1  ; shift
CMD="$*"

fail() {
  echo "cronwrap: FATAL $*"
  exit 32
}

if [ -z "${NAME}" ] || \
   [ -z "${INT}"  ] || \
   [ -z "${CMD}"  ] ; then
   usage
fi

LOG_DIR=${CRONWRAP_LOG_DIR:-/var/log/cronwrap}
CRON_DIR=${LOG_DIR}/${NAME}
LOCK_DIR=${CRONWRAP_LOCK_DIR:-${CRON_DIR}}
STATUS_DIR=${CRON_DIR}/status
LOCK_NAME=${CRONWRAP_LOCK_NAME:-${NAME}}
LOCK=${LOCK_DIR}/${LOCK_NAME}.lock
HOST=$( uname -n )
PATH=${CRONWRAP_PATH:-${PATH}}

QUIET_LOCK=${CRONWRAP_QUIET_LOCK:-}

STAMP=$( date '+%Y%m%d-%H%M%S' )

command -v lockf > /dev/null 2>&1 || fail "can't find lockf(0)"

mkdir -p "${LOG_DIR}"    || fail "couldn't create ${LOG_DIR}"
mkdir -p "${LOCK_DIR}"   || fail "couldn't create ${LOCK_DIR}"
mkdir -p "${STATUS_DIR}" || fail "couldn't create ${STATUS_DIR}"
LOG=${CRON_DIR}/${STAMP}.log
TMP=${CRON_DIR}/$$.log # feeble, but gives us route back to the running job

touch "${STATUS_DIR}/job_ok"
touch "${STATUS_DIR}/job_fail"
touch "${STATUS_DIR}/lock_fail"

echo "${STAMP}" > "${STATUS_DIR}/last_attempt"
echo "${INT}"   > "${STATUS_DIR}/interval"

# shellcheck disable=2129
date > "${TMP}"
# shellcheck disable=2129
echo "host: ${HOST}"    >> "${TMP}"
echo "name: ${NAME}"    >> "${TMP}"
echo "interval: ${INT}" >> "${TMP}"
echo "command: ${CMD}"  >> "${TMP}"
echo "wrapped: lockf -s -t 0 ${LOCK} ${CMD}" >> "${TMP}"

echo >> "${TMP}"

lockf -s -t 0 "${LOCK}" "$@" >> "${TMP}" 2>&1
EXIT=$?

echo >> "${TMP}"

if [ ${EXIT} -eq 75 ] ; then # EX_TEMPFAIL
  # run was locked

  if [ -z "${QUIET_LOCK}" ] ; then
    echo "failed: lockf indicated earlier process running" >> "${TMP}"
    mv "${TMP}" "${LOG}"

    ln -nsf "${LOG}" "${CRON_DIR}/last_run"
    ln -nsf "${LOG}" "${CRON_DIR}/last_lock_fail"
    rm -f "${STATUS_DIR}/OK"
    rm -f "${STATUS_DIR}/FAIL"
    echo "${STAMP}" >  "${STATUS_DIR}/LOCK"
    echo "${STAMP}" >> "${STATUS_DIR}/lock_fail"
  else
    echo "failed: lockf indicated earlier process running (quiet lock mode)" >> "${TMP}"
    mv "${TMP}" "${LOG}"

    # in quiet mode we link the log as lock_fail and touch the lock_fail marker
    # but set the overall status as OK
    ln -nsf "${LOG}" "${CRON_DIR}/last_run"
    ln -nsf "${LOG}" "${CRON_DIR}/last_lock_fail"
    rm -f "${STATUS_DIR}/LOCK"
    rm -f "${STATUS_DIR}/FAIL"
    echo "${STAMP}" >  "${STATUS_DIR}/OK"
    echo "${STAMP}" >> "${STATUS_DIR}/lock_fail"
  fi

  if [ -n "${DEBUG}" ] ; then
    echo lock_fail
    echo
    cat "${LOG}"
  fi
  exit 1
fi

if [ "${EXIT}" -gt 0 ] ; then
  # command ran, but errored
  echo "failed: command exited non-zero" >> "${TMP}"
  mv "${TMP}" "${LOG}"
  ln -nsf "${LOG}" "${CRON_DIR}/last_run"
  ln -nsf "${LOG}" "${CRON_DIR}/last_job_fail"
  rm -f "${STATUS_DIR}/OK"
  rm -f "${STATUS_DIR}/LOCK"
  echo "${STAMP}" >  "${STATUS_DIR}/FAIL"
  echo "${STAMP}" >> "${STATUS_DIR}/job_fail"

  if [ -n "${DEBUG}" ] ; then
    echo job_fail
    echo
    cat "${LOG}"
  fi
  exit 2
fi

echo "success: job exited ok" >> "${TMP}"
mv "${TMP}" "${LOG}"
ln -nsf "${LOG}" "${CRON_DIR}/last_run"
ln -nsf "${LOG}" "${CRON_DIR}/last_job_ok"
rm -f "${STATUS_DIR}/FAIL"
rm -f "${STATUS_DIR}/LOCK"
echo "${STAMP}" >  "${STATUS_DIR}/OK"
echo "${STAMP}" >> "${STATUS_DIR}/job_ok"

if [ -n "${DEBUG}" ] ; then
  echo job_ok
  echo
  cat "${LOG}"
fi

exit 0