# (C) Copyright 2014-2017 Hewlett Packard Enterprise Development LP
# Copyright 2017 FUJITSU LIMITED
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Persister Module

   The Persister reads metrics and alarms from Kafka and then stores them
   in into either Influxdb or Cassandra

   Start the perister as stand-alone process by running 'persister.py
   --config-file <config file>'
"""
import multiprocessing
import os
import signal
import sys
import time

from monasca_common.simport import simport
from oslo_config import cfg
from oslo_log import log

from monasca_persister import config
from monasca_persister.repositories import persister


LOG = log.getLogger(__name__)

processors = []  # global list to facilitate clean signal handling
exiting = False


def clean_exit(signum, frame=None):
    """Exit all processes attempting to finish uncommitted active work before exit.
         Can be called on an os signal or no zookeeper losing connection.
    """
    global exiting
    if exiting:
        # Since this is set up as a handler for SIGCHLD when this kills one
        # child it gets another signal, the global exiting avoids this running
        # multiple times.
        LOG.debug('Exit in progress clean_exit received additional signal %s' % signum)
        return

    LOG.info('Received signal %s, beginning graceful shutdown.' % signum)
    exiting = True
    wait_for_exit = False

    for process in processors:
        try:
            if process.is_alive():
                process.terminate()  # Sends sigterm which any processes after a notification is sent attempt to handle
                wait_for_exit = True
        except Exception:  # nosec
            # There is really nothing to do if the kill fails, so just go on.
            # The # nosec keeps bandit from reporting this as a security issue
            pass

    # wait for a couple seconds to give the subprocesses a chance to shut down correctly.
    if wait_for_exit:
        time.sleep(2)

    # Kill everything, that didn't already die
    for child in multiprocessing.active_children():
        LOG.debug('Killing pid %s' % child.pid)
        try:
            os.kill(child.pid, signal.SIGKILL)
        except Exception:  # nosec
            # There is really nothing to do if the kill fails, so just go on.
            # The # nosec keeps bandit from reporting this as a security issue
            pass

    if signum == signal.SIGTERM:
        sys.exit(0)

    sys.exit(signum)


def start_process(respository, kafka_config):
    LOG.info("start process: {}".format(respository))
    m_persister = persister.Persister(kafka_config, cfg.CONF.zookeeper,
                                      respository)
    m_persister.run()


def prepare_processes(conf, repo_driver):
    if conf.num_processors > 0:
        repository = simport.load(repo_driver)
        for proc in range(0, conf.num_processors):
            processors.append(multiprocessing.Process(
                target=start_process, args=(repository, conf)))

def main():
    """Start persister."""

    config.parse_args()

    # Add processors for metrics topic
    if cfg.CONF.kafka_metrics.enabled:
        prepare_processes(cfg.CONF.kafka_metrics,
                          cfg.CONF.repositories.metrics_driver)
    # Add processors for alarm history topic
    if cfg.CONF.kafka_alarm_history.enabled:
        prepare_processes(cfg.CONF.kafka_alarm_history,
                          cfg.CONF.repositories.alarm_state_history_driver)
    # Add processors for events topic
    if cfg.CONF.kafka_events.enabled:
        prepare_processes(cfg.CONF.kafka_events,
                          cfg.CONF.repositories.events_driver)

    # Start
    try:
        LOG.info('''

               _____
              /     \   ____   ____ _____    ______ ____ _____
             /  \ /  \ /  _ \ /    \\\__  \  /  ___// ___\\\__  \\
            /    Y    (  <_> )   |  \/ __ \_\___ \\  \___ / __  \\_
            \____|__  /\____/|___|  (____  /____  >\___  >____  /
                    \/            \/     \/     \/     \/     \/
            __________                    .__          __
            \______   \ ___________  _____|__| _______/  |_  ___________
             |     ___// __ \_  __ \/  ___/  |/  ___/\   __\/ __ \_  __ \\
             |    |   \  ___/|  | \/\___ \|  |\___ \  |  | \  ___/|  | \/
             |____|    \___  >__|  /____  >__/____  > |__|  \___  >__|
                           \/           \/        \/            \/

        ''')
        for process in processors:
            process.start()

        # The signal handlers must be added after the processes start otherwise
        # they run on all processes
        signal.signal(signal.SIGCHLD, clean_exit)
        signal.signal(signal.SIGINT, clean_exit)
        signal.signal(signal.SIGTERM, clean_exit)

        while True:
            time.sleep(10)

    except Exception:
        LOG.exception('Error! Exiting.')
        clean_exit(signal.SIGKILL)

if __name__ == "__main__":
    sys.exit(main())
