Gunicorn init script for Gentoo that checks liveliness properly

gistfile1.eclass

#!/sbin/runscript

[[ -z "${PIDFILE}" ]] && PIDFILE="/var/run/gunicorn/${SVCNAME}.pid"
[[ -z "${BINARY}" ]] && BINARY="/usr/bin/gunicorn"

depend() {
    need net
    use dns logger netmount
}

check_params() {
    if [[ "${SVCNAME}" == "gunicorn" && -z "${I_KNOW}" ]]; then
        ewarn "It is highly recommended to use a symbolic link for this"
        ewarn "script and start via that instead. This allows you to run"
        ewarn "multiple spawn services simultaneously. To do this, simply:"
        ewarn
        ewarn "  ln -s /etc/init.d/gunicorn /etc/init.d/gunicorn.mysvc"
        ewarn "  cp /etc/conf.d/gunicorn /etc/conf.d/gunicorn.mysvc"
        ewarn
        ewarn "If you don't want to be bothered by this message, set I_KNOW=yes"
        ewarn "in your configuration file."
        ewarn
    fi

    if [[ -z "${WSGI_APP}" ]] && [[ -z "${WSGI_TYPE}" ]]; then
        eerror "${WSGI_APP} not set. Exiting"
        return 1
    fi

    if [[ -z "${PIDFILE}" ]]; then
        eerror "PIDFILE must be set in /etc/conf.d/${SVCNAME}"
        return 1
    fi
}

test_pidfile() {
    if [[ ! -f "${PIDFILE}" ]]; then
        eerror "${PIDFILE} does not exist"
        return 1
    fi

    read -r PID <"${PIDFILE}"

    if [[ -z "${PID}" ]]; then
        eerror "${PIDFILE} contains no PID"
        return 1
    fi

    if [[ ! -d "/proc/${PID}" ]]; then
        eerror "${PID} does not appear to be an existing process"
        return 1
    fi

    if awk -F: 'BEGIN { found = 0; } END { exit(found); }; $1 == "State" && $2 !~ /^[[:space:]]*Z / { found = 1; };' "/proc/${PID}/status"; then
        eerror "${PID} does not appear to be an active process"
        return 1
    fi

    return 0
}

kill_pidfile() {
    check_params && test_pidfile || return 1

    ebegin "$1"
    shift
    read -r PID <"${PIDFILE}"
    kill "$@" "${PID}"
    local RC=$?
    eend $RC

    return $RC
}

# actions

start() {
    check_params || return 1

    local -a OPTS
    OPTS=( "-c" "${CONFIG}"
           "--daemon"
           "--pid=${PIDFILE}"
           "${WSGI_APP}" )

    ebegin "Starting ${SVCNAME} using ${CONFIG}"
    env PYTHONPATH="${PYTHONPATH}" "${BINARY}" "${OPTS[@]}"
    local RC=$?
    eend "${RC}"

    if [[ "${RC}" == 0 ]]; then
        ebegin "No early errors, checking liveliness"
        sleep 1
        if ! test_pidfile; then
            eend 1
            return 1
        fi
        eend 0
    fi

    return "${RC}"
}

status() {
    check_params && test_pidfile
}

stop() {
    kill_pidfile "Stopping (gracefully) ${SVCNAME}" \
                 -s SIGQUIT
}

force_stop() {
    kill_pidfile "Stopping (disregarding jobs) ${SVCNAME}" \
                 -s SIGINT
}

reload() {
    kill_pidfile "Telling ${SVCNAME} to reload itself" \
                 -s SIGHUP
}

opts="${opts} status reload force_stop"

How to use

1. Save as /etc/init.d/gunicorn

2. Create a basic configuration at /etc/conf.d/gunicorn that says:

   WSGI_APP=myapp:foo
   CONFIG=/etc/gunicorn/some-service-config.py
   #PYTHONPATH=extra_path
   #PIDFILE=pidfile_override
   

3. Do as advised and create a symlink at /etc/init.d/gunicorn.mysvc -> gunicorn and copy the configuration template.

4. Edit configuration, done.

Why would you use

Most init scripts suffer from the ailment that they don't actually know if the
daemon they control is living or not. This is a fundamental flaw, and the way
things are handled there is really no way to ascertain liveliness of Python
daemons because they run as the process "python", and start-stop-daemon
relies on pidof and other dumb trickery. (Feel free to tell me off if you
know of a good way to do this with start-stop-daemon.)

This script takes the stance that checking /proc/$pid/status isn't actually
hard and can be done on a per-script basis. This yields the following desirable
behavior:

mysvc $ sudo /etc/init.d/gunicorn.mysvc start
 * Starting gunicorn.mysvc using /etc/gunicorn/mysvc.conf.py ...         [ ok ]
 * No early errors, checking liveliness ...                              [ ok ]
mysvc $ sudo /etc/init.d/gunicorn.mysvc status
 * status:  started
mysvc $ sudo kill $(cat /var/run/gunicorn/gunicorn.mysvc.pid)
mysvc $ sudo /etc/init.d/gunicorn.mysvc status
 * status:  started
 * /var/run/gunicorn/gunicorn.mysvc.pid does not exist

The init system is still a little dumb--it thinks the service is started even
though the status function returns non-zero--the script tells you something is
amiss. In this case the correct solution is to zap and start the service
again, since stop will fail due to there being no pidfile.