client.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright (c) 2012, 2013, 2014, 2015, 2016
#
# Author(s):
#
#   Martin Raspaud <martin.raspaud@smhi.se>
#   Panu Lahtinen <panu.lahtinen@fmi.fi>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""Trollmoves client."""
import argparse
import logging
import os
import socket
import time
from collections import deque
from configparser import ConfigParser
from threading import Lock, Thread, Event
import hashlib
from urllib.parse import urlparse, urlunparse
import subprocess
from contextlib import suppress

import tarfile
from zmq import LINGER, POLLIN, REQ, Poller
import bz2
from posttroll import get_context
from posttroll.message import Message, MessageError
from posttroll.publisher import create_publisher_from_dict_config
from posttroll.subscriber import Subscriber
from trollsift.parser import compose

from trollmoves import heartbeat_monitor
from trollmoves.logging import add_logging_options_to_parser
from trollmoves.move_it_base import MoveItBase
from trollmoves.utils import get_local_ips
from trollmoves.utils import gen_dict_extract, translate_dict
from trollmoves.movers import CTimer

LOGGER = logging.getLogger(__name__)

file_cache = deque(maxlen=11000)
cache_lock = Lock()
ongoing_transfers = dict()
ongoing_transfers_lock = Lock()
hot_spare_timer_lock = Lock()
ongoing_hot_spare_timers = dict()

DEFAULT_REQ_TIMEOUT = 1
SERVER_HEARTBEAT_TOPIC = "/heartbeat/move_it_server"
CLIENT_HEARTBEAT_TOPIC_BASE = "/heartbeat/move_it"

COMPRESSED_ENDINGS = {'xrit': ['C_'],
                      'tar': ['.tar', '.tar.gz', '.tgz', '.tar.bz2'],
                      'bzip': ['.bz2'],
                      }
BUNZIP_BLOCK_SIZE = 1024
LISTENER_CHECK_INTERVAL = 1


def is_localhost(host):
    """Check if host is localhost."""
    return socket.gethostbyname(host) in get_local_ips()


def read_config(filename):
    """Read the config file called *filename*."""
    cp_ = ConfigParser(interpolation=None)
    with open(filename) as config_file:
        cp_.read_file(config_file)

    res = {}

    for section in cp_.sections():
        res[section] = dict(cp_.items(section))
        _set_config_defaults(res[section])
        _parse_boolean_config_items(res[section], cp_[section])
        _parse_nameservers(res[section], cp_[section])
        _parse_backup_targets(res[section], cp_[section])
        if not _check_provider_config(res, section):
            continue
        if not _check_destination(res, section):
            continue
        if not _check_subscribing(res, section):
            continue

    return res


def _set_config_defaults(conf):
    conf.setdefault("delete", False)
    conf.setdefault("working_directory", None)
    conf.setdefault("compression", False)
    conf.setdefault("xritdecompressor", None)
    conf.setdefault("heartbeat", True)
    conf.setdefault("req_timeout", DEFAULT_REQ_TIMEOUT)
    conf.setdefault("transfer_req_timeout", 10 * DEFAULT_REQ_TIMEOUT)
    conf.setdefault("nameservers", None)
    conf.setdefault("create_target_directory", True)
    conf.setdefault("backup_targets", None)


def _parse_boolean_config_items(conf, raw_conf):
    for key in ["delete", "heartbeat", "create_target_directory"]:
        try:
            val = raw_conf.getboolean(key)
        except ValueError:
            continue
        if val is not None:
            conf[key] = val


def _parse_nameservers(conf, raw_conf):
    try:
        val = raw_conf.getboolean("nameservers")
    except ValueError:
        val = conf["nameservers"]
    if isinstance(val, str):
        val = val.split()
    conf["nameservers"] = val


def _parse_backup_targets(conf, raw_conf):
    val = raw_conf.get("backup_targets")
    if isinstance(val, str):
        val = val.split()
    conf["backup_targets"] = val


def _check_provider_config(conf, section):
    if "providers" not in conf[section]:
        LOGGER.warning("Incomplete section %s: add an 'providers' item.",
                       section)
        LOGGER.info("Ignoring section %s: incomplete.",
                    section)
        del conf[section]
        return False

    conf[section]["providers"] = [
        "tcp://" + item.split('/', 1)[0] for item in conf[section]["providers"].split()
    ]
    return True


def _check_subscribing(res, section):
    if "topic" in res[section]:
        try:
            res[section]["publish_port"] = int(res[section][
                "publish_port"])
        except (KeyError, ValueError):
            res[section]["publish_port"] = 0
    elif not res[section]["heartbeat"]:
        # We have no topics and therefor no subscriber (if you want to
        # subscribe everything, then explicit specify an empty topic).
        LOGGER.warning("Incomplete section %s: add an 'topic' "
                       "item or enable heartbeat.", section)
        LOGGER.info("Ignoring section %s: incomplete.", section)
        del res[section]
        return False
    return True


def _check_destination(res, section):
    if "destination" not in res[section]:
        LOGGER.warning("Incomplete section %s: add an 'destination' item.",
                       section)
        LOGGER.info("Ignoring section %s: incomplete.", section)
        del res[section]
        return False
    return True


class Listener(Thread):
    """PyTroll listener class for reading messages for Trollduction."""

    def __init__(self, address, topics, *args, die_event=None, **kwargs):
        """Init Listener object."""
        super().__init__()

        self.topics = topics
        self.subscriber = None
        self.address = address
        self.running = False
        self.die_event = die_event
        self.cargs = args
        self.ckwargs = kwargs
        self.restart_event = Event()
        self.cause_of_death = None
        self.death_count = 0

    def restart(self):
        """Restart the listener, returns a new running instance."""
        self.stop()
        new_listener = self.__class__(self.address, self.topics, *self.cargs,
                                      die_event=self.die_event, **self.ckwargs)
        new_listener.death_count = self.death_count + 1
        new_listener.start()
        return new_listener

    def create_subscriber(self):
        """Create a subscriber using specified addresses and message types."""
        if self.subscriber is None:
            if self.topics:
                LOGGER.info("Subscribing to %s with topics %s",
                            str(self.address), str(self.topics))
                self.subscriber = Subscriber(self.address, self.topics)
                LOGGER.debug("Subscriber %s", str(self.subscriber))

    def run(self):
        """Run listener."""
        try:
            with heartbeat_monitor.Monitor(self.restart_event, **self.ckwargs) as beat_monitor:
                self.running = True
                while self.running:
                    LOGGER.debug("Starting listener %s", str(self.address))
                    self.create_subscriber()
                    self._get_messages(beat_monitor)
        except Exception as err:
            LOGGER.exception("Listener died.")
            self.cause_of_death = err
            with suppress(AttributeError):
                self.die_event.set()

    def _get_messages(self, beat_monitor):
        for msg in self.subscriber(timeout=1):
            if not self.running:
                break
            if not self._check_heartbeat():
                break
            if msg is None:
                continue

            LOGGER.debug("Receiving (SUB) %s", str(msg))

            beat_monitor(msg)

            if self._is_message_already_handled(msg):
                continue

            self._process_message(msg)

        LOGGER.debug("Exiting listener %s", str(self.address))

    def _check_heartbeat(self):
        if self.restart_event.is_set():
            LOGGER.warning("Missing a heartbeat, restarting the subscriber to %s.",
                           str(self.subscriber.addresses))
            self.restart_event.clear()
            self.stop()
            self.running = True
            return False
        return True

    def _is_message_already_handled(self, msg):
        return (self._handle_beat_message(msg) or _handle_push_message(msg) or
                _handle_ack_message(msg) or _handle_message_from_another_client(msg))

    def _handle_beat_message(self, msg):
        if msg.type == "beat":
            self.death_count = 0
            return True
        return False

    def _process_message(self, msg):
        delay = self.ckwargs.get("processing_delay", False)
        backup_targets = self.ckwargs.get('backup_targets', None)
        if backup_targets:
            LOGGER.debug("Adding backup_targets %s to the message.", str(backup_targets))
            msg.data['backup_targets'] = backup_targets
        if delay:
            # If this is a hot spare client, wait for a while
            # for a public "push" message which will update
            # the ongoing transfers before starting processing here
            add_request_push_timer(float(delay), msg, *self.cargs, **self.ckwargs)
        else:
            request_push(msg, *self.cargs, **self.ckwargs)

    def stop(self):
        """Stop subscriber and delete the instance."""
        self.running = False
        time.sleep(1)
        if self.subscriber is not None:
            self.subscriber.close()
            self.subscriber = None


def _handle_push_message(msg):
    if msg.type == "push":
        # TODO: these need to be checked and acted if
        # the transfers are not finished on primary
        # client and are not cleared
        LOGGER.debug("Primary client published 'push'")
        add_to_ongoing_transfers(msg)
        return True
    return False


def _handle_ack_message(msg):
    if msg.type == "ack":
        LOGGER.debug("Primary client finished transfer")
        _ = add_to_file_cache(msg)
        _ = clean_ongoing_transfer(get_msg_uid(msg))
        return True
    return False


def _handle_message_from_another_client(msg):
    if msg.type == "file" and "request_address" not in msg.data:
        LOGGER.debug("Ignoring 'file' message from primary client.")
        add_to_ongoing_transfers(msg)
        _ = add_to_file_cache(msg)
        _ = clean_ongoing_transfer(get_msg_uid(msg))
        return True
    return False


def clean_ongoing_transfer(uid):
    """Clear transfer for the given UID from the cache."""
    with ongoing_transfers_lock:
        msgs = ongoing_transfers.pop(uid, [])
        LOGGER.debug("Remove uid %s: %s", uid, str(msgs))
    return msgs


def unpack_tar(filename, **kwargs):
    """Unpack tar files."""
    destdir = os.path.dirname(filename)
    try:
        with tarfile.open(filename) as tar:
            tar.extractall(destdir)
            members = tar.getmembers()
    except tarfile.ReadError as err:
        raise IOError(str(err))
    fnames = tuple(os.path.join(destdir, member.name) for member in members)
    if len(fnames) == 1:
        return fnames[0]
    return fnames


def unpack_xrit(filename, **kwargs):
    """Unpack XRIT files."""
    if filename.endswith('__'):
        return filename
    cmd = kwargs.get('xritdecompressor')
    if cmd is None:
        raise OSError("Path to 'xRITDecompress' utility not defined. "
                      "Set it with 'xritdecompressor' config option.")
    destdir = os.path.dirname(filename)
    out_fname = os.path.join(destdir, os.path.basename(filename)[:-2] + "__")
    check_output([cmd, filename], cwd=(destdir))
    return out_fname


def unpack_bzip(filename, **kwargs):
    """Unzip .bz2 files."""
    block_size = int(kwargs.get('block_size', BUNZIP_BLOCK_SIZE))
    out_fname = filename[:-4]
    if os.path.exists(out_fname):
        return out_fname
    with open(out_fname, "wb") as dest:
        try:
            orig = bz2.BZ2File(filename, "r")
            while True:
                block = orig.read(block_size)

                if not block:
                    break
                dest.write(block)
            LOGGER.debug("Bunzipped %s to %s", filename, out_fname)
        finally:
            orig.close()
    return out_fname


def check_output(*popenargs, **kwargs):
    """Copy from python 2.7, `subprocess.check_output`."""
    if 'stdout' in kwargs:
        raise ValueError('stdout argument not allowed, it will be overridden.')
    LOGGER.debug("Calling %s", str(popenargs))
    process = subprocess.Popen(stdout=subprocess.PIPE, *popenargs, **kwargs)
    output, unused_err = process.communicate()
    del unused_err
    retcode = process.poll()
    if retcode:
        cmd = kwargs.get("args")
        if cmd is None:
            cmd = popenargs[0]
        raise RuntimeError(output)
    return output


unpackers = {'tar': unpack_tar,
             'xrit': unpack_xrit,
             'bzip': unpack_bzip}


def already_received(msg):
    """Check if the files from msg already are in the local cache."""
    with cache_lock:
        for filename in gen_dict_extract(msg.data, 'uid'):
            if filename not in file_cache:
                return False
        else:
            return True


def resend_if_local(msg, publisher):
    """Resend the message provided all uris point to local files."""
    for uri in gen_dict_extract(msg.data, 'uri'):
        urlobj = urlparse(uri)
        if not publisher or not is_localhost(urlobj.netloc):
            return

    LOGGER.debug('Sending: %s', str(msg))
    publisher.send(str(msg))


def create_push_req_message(msg, destination, login):
    """Create a message for push request."""
    fake_req = Message(msg.subject, 'push', data=msg.data.copy())
    duri = urlparse(destination)
    scheme = duri.scheme or 'file'
    dest_hostname = duri.hostname or socket.gethostname()
    if duri.port:
        dest_hostname += ":{}".format(duri.port)
    fake_req.data["destination"] = urlunparse((scheme, dest_hostname, duri.path, "", "", ""))
    if login:
        # if necessary add the credentials for the real request
        req = Message(msg.subject, 'push', data=msg.data.copy())
        req.data["destination"] = urlunparse((scheme, login + "@" + dest_hostname, duri.path, "", "", ""))
    else:
        req = fake_req
    return req, fake_req


def create_local_dir(destination, local_root, mode=0o777):
    """Create the local directory if it doesn't exist and return that path."""
    duri = urlparse(destination)
    if duri.scheme in ('s3'):
        return None
    local_dir = os.path.join(*([local_root] + duri.path.split(os.path.sep)))

    if not os.path.exists(local_dir):
        os.makedirs(local_dir)
        os.chmod(local_dir, mode)
    return local_dir


def unpack_and_create_local_message(msg, local_dir, **kwargs):
    """Unpack the file(s) given in the message, and return an updated message."""
    def unpack_callback(var, **kwargs):
        unpack = kwargs.get('compression')
        endings = COMPRESSED_ENDINGS[unpack]
        is_compressed = any([var['uid'].endswith(ending) for ending in endings])
        if not is_compressed:
            return var
        packname = var.pop('uid')
        del var['uri']
        new_names = unpackers[unpack](os.path.join(local_dir, packname),
                                      **kwargs)
        if kwargs.get("delete"):
            LOGGER.debug("Deleting %s", os.path.join(local_dir, packname))
            os.remove(os.path.join(local_dir, packname))
        if isinstance(new_names, tuple):
            var['dataset'] = [dict(uid=os.path.basename(nn),
                                   uri=os.path.join(local_dir, nn))
                              for nn in new_names]
        else:
            var['uid'] = os.path.basename(new_names)
            var['uri'] = os.path.join(local_dir, new_names)
        return var

    if kwargs.get('compression') in COMPRESSED_ENDINGS:
        lmsg_data = translate_dict(msg.data, ('uri', 'uid'), unpack_callback,
                                   **kwargs)
        if 'dataset' in lmsg_data:
            lmsg_type = 'dataset'
        elif 'collection' in lmsg_data:
            lmsg_type = 'collection'
        else:
            lmsg_type = 'file'
    else:
        lmsg_data = msg.data.copy()
        lmsg_type = msg.type

    return Message(msg.subject, lmsg_type, data=lmsg_data)


def make_uris(msg, destination, login=None):
    """Create local URIs for the received files."""
    duri = urlparse(destination)
    scheme = duri.scheme
    netloc = duri.netloc
    if scheme != "s3" and empty_or_localhost(duri.hostname):
        scheme = ""
        netloc = ""
    elif netloc:
        if login:
            # Add (only) user to uri.
            netloc = login.split(":")[0] + "@" + netloc

    def uri_callback(var):
        uid = var['uid']
        path = os.path.join(duri.path, uid)
        var['uri'] = urlunparse((scheme, netloc, path, "", "", ""))
        return var
    msg.data = translate_dict(msg.data, ('uri', 'uid'), uri_callback)
    return msg


def empty_or_localhost(hostname):
    """Check that hostname is either empty or referring to localhost."""
    return ((not hostname) or (hostname and is_localhost(hostname)))


def replace_mda(msg, kwargs):
    """Replace message metadata with items in kwargs dict."""
    for key in msg.data:
        if key in kwargs:
            try:
                replacement = dict(item.split(':') for item in kwargs[key].split('|'))
                replacement = replacement[msg.data[key]]
            except (ValueError, AttributeError):
                replacement = kwargs[key]
            msg.data[key] = replacement
    return msg


def send_request(msg, req, timeout):
    """Send a request for push."""
    LOGGER.debug("Send and recv timeout is %.2f seconds", timeout)

    hostname, port = msg.data["request_address"].split(":")
    requester = PushRequester(hostname, int(port))
    return requester.send_and_recv(req, timeout=timeout), hostname


def send_ack(msg, timeout):
    """Send an ACK (no push required)."""
    req = Message(msg.subject, 'ack', data=msg.data)
    LOGGER.debug("Sending: %s", str(req))

    response, hostname = send_request(msg, req, timeout)

    if response and response.type == "ack":
        pass
    else:
        LOGGER.error("Failed to get valid response from server %s: %s",
                     str(hostname), str(response))


def terminate_transfers(uid, timeout):
    """Send ACK to remaining sources for uid and remove from the ongoing tranfers list."""
    msgs = clean_ongoing_transfer(uid)
    for msg in msgs:
        send_ack(msg, timeout)


def get_msg_uid(msg):
    """Compute the uid of the message."""
    filenames = sorted(gen_dict_extract(msg.data, 'uid'))
    m = hashlib.md5()
    for filename in filenames:
        m.update(filename.encode('utf-8'))
    return m.hexdigest()


def iterate_messages(uid):
    """Iterate over all messages for a uid."""
    while True:
        try:
            msg = get_next_msg(uid)
        except IndexError:
            return
        yield msg


def get_next_msg(uid):
    """Get the next message with this *uid* from the available sources."""
    with ongoing_transfers_lock:
        return ongoing_transfers[uid].pop(0)


def add_request_push_timer(timeout, msg, *args, **kwargs):
    """Add a timer for hot spare."""
    huid = get_msg_uid(msg)
    cargs = [msg] + list(args)
    with hot_spare_timer_lock:
        timer = CTimer(timeout, request_push, args=cargs, kwargs=kwargs)
        ongoing_hot_spare_timers[huid] = timer
        ongoing_hot_spare_timers[huid].start()
    LOGGER.debug("Added timer for UID %s.", huid)


def add_to_ongoing_transfers(msg):
    """Add message to ongoing transfers.

    Return None if similar message was already received, otherwise the hashed uid of the message.
    """
    hashed_uid = get_msg_uid(msg)
    with hot_spare_timer_lock:
        timer = ongoing_hot_spare_timers.pop(hashed_uid, None)
        if timer is not None:
            timer.cancel()
            LOGGER.debug("Cleared timer for UID %s.", hashed_uid)
    with ongoing_transfers_lock:
        if hashed_uid in ongoing_transfers:
            ongoing_transfers[hashed_uid].append(msg)
            return None
        ongoing_transfers[hashed_uid] = [msg]
        return hashed_uid


def add_to_file_cache(msg):
    """Add files in the message to received file cache."""
    with cache_lock:
        for uid in gen_dict_extract(msg.data, 'uid'):
            if uid not in file_cache:
                LOGGER.debug("Add %s to file cache", str(uid))
                file_cache.append(uid)


def request_push(msg_in, destination, login=None, publisher=None, **kwargs):
    """Request a push for data."""
    hashed_uid = add_to_ongoing_transfers(msg_in)
    if hashed_uid is None:
        return

    if already_received(msg_in):
        timeout = float(kwargs["req_timeout"])
        send_ack(msg_in, timeout)
        _ = clean_ongoing_transfer(hashed_uid)
        return

    _request_files(hashed_uid, destination, login, publisher, **kwargs)


def _request_files(hashed_uid, destination, login, publisher, **kwargs):
    for msg in iterate_messages(hashed_uid):
        _destination = _compose_destination(destination, msg)

        req, no_credentials_req = create_push_req_message(msg, _destination, login)
        LOGGER.info("Requesting: %s", str(no_credentials_req))
        if kwargs.get('create_target_directory', True):
            local_dir = create_local_dir(_destination, kwargs.get('ftp_root', '/'))
        else:
            local_dir = None

        publisher.send(str(no_credentials_req))

        response, hostname = send_request(msg, req, float(kwargs["transfer_req_timeout"]))

        if response and response.type in ['file', 'collection', 'dataset']:
            LOGGER.debug("Server done sending file")
            add_to_file_cache(msg)
            _send_ack_message(msg, publisher)

            try:
                lmsg = unpack_and_create_local_message(response, local_dir, **kwargs)
                lmsg = _update_local_message(lmsg, _destination, login, response, **kwargs)
            except IOError:
                LOGGER.exception("Couldn't unpack %s", str(response))
                continue

            LOGGER.debug("publishing %s", str(lmsg))
            publisher.send(str(lmsg))
            terminate_transfers(hashed_uid, float(kwargs["req_timeout"]))
            break
        else:
            LOGGER.error("Failed to get valid response from server %s: %s",
                         str(hostname), str(response))
    else:
        LOGGER.warning('Could not get a working source for requesting %s',
                       str(msg))
        terminate_transfers(hashed_uid, float(kwargs["req_timeout"]))


def _compose_destination(destination, msg):
    try:
        _destination = compose(destination, msg.data)
    except KeyError as ke:
        LOGGER.error("Format identifier is missing from the msg.data: %s", str(ke))
        raise
    except ValueError as ve:
        LOGGER.error("Type of format identifier doesn't match the type in m msg.data: %s", str(ve))
        raise
    except AttributeError as ae:
        LOGGER.error("msg or msg.data is None: %s", str(ae))
        raise
    return _destination


def _send_ack_message(msg, publisher):
    """Send an 'ack' message.

    This is for the possible hot spare clients so they know the primary has completed the request.
    """
    msg = Message(msg.subject, 'ack', msg.data)
    LOGGER.debug("Sending a public 'ack' of completed transfer: %s", str(msg))
    publisher.send(str(msg))


def _update_local_message(lmsg, _destination, login, response, **kwargs):
    lmsg = make_uris(lmsg, _destination, login)
    lmsg.data['origin'] = response.data['request_address']
    lmsg.data.pop('request_address', None)
    lmsg = replace_mda(lmsg, kwargs)
    lmsg.data.pop('destination', None)

    return lmsg


class Chain(Thread):
    """The Chain class."""

    def __init__(self, name, config):
        """Init a chain object."""
        super().__init__()
        self._config = config
        self._name = name
        self.publisher = None
        self._pub_starter = None
        self.listeners = {}
        self.listener_died_event = Event()
        self.running = True
        self.setup_publisher()

    def setup_publisher(self):
        """Initialize publisher."""
        if self.publisher is None:
            with suppress(KeyError, NameError):
                nameservers = self._config["nameservers"]
                pub_settings = {
                    "name": "move_it_" + self._name,
                    "port": self._config["publish_port"],
                    "nameservers": nameservers,
                }
                self._pub_starter = create_publisher_from_dict_config(pub_settings)
                self.publisher = self._pub_starter.start()

    def setup_listeners(self, keep_providers=None):
        """Set up the listeners."""
        keep_providers = keep_providers or []
        try:
            topics = []
            if "topic" in self._config:
                topics.append(self._config["topic"])
            if self._config.get("heartbeat", False):
                topics.append(SERVER_HEARTBEAT_TOPIC)
                # Subscribe also to heartbeat messages of other clients
                topics.append(CLIENT_HEARTBEAT_TOPIC_BASE + '_' + self._name)
            for provider in self._config["providers"]:
                if provider in keep_providers and provider in self.listeners:
                    LOGGER.debug("Not restarting Listener to %s, config not changed.", provider)
                    continue
                if '/' in provider.split(':')[-1]:
                    parts = urlparse(provider)
                    if parts.scheme != '':
                        provider = urlunparse((parts.scheme, parts.netloc,
                                               '', '', '', ''))
                    else:
                        # If there's no scheme, urlparse thinks the
                        # URI is a local file
                        provider = urlunparse(('tcp', parts.path,
                                               '', '', '', ''))
                    topics.append(parts.path)
                LOGGER.debug("Add listener for %s with topic %s",
                             provider, str(topics))
                listener = Listener(
                    provider,
                    topics,
                    publisher=self.publisher,
                    die_event=self.listener_died_event,
                    **self._config)
                listener.start()
                self.listeners[provider] = listener
        except Exception as err:
            LOGGER.exception(str(err))
            raise

    def restart_dead_listeners(self):
        """Restart dead listeners."""
        plural = ['', 's']
        for provider in list(self.listeners.keys()):
            if not self.listeners[provider].is_alive():
                cause_of_death = self.listeners[provider].cause_of_death
                death_count = self.listeners[provider].death_count
                while death_count < 3:
                    LOGGER.error("Listener for %s died %d time%s: %s", provider, death_count + 1,
                                 plural[min(death_count, 1)], str(cause_of_death))
                    self.listeners[provider] = self.listeners[provider].restart()
                    time.sleep(.5)
                    if not self.listeners[provider].is_alive():
                        death_count = self.listeners[provider].death_count
                        cause_of_death = self.listeners[provider].cause_of_death
                    else:
                        break
                if death_count >= 3:
                    with suppress(Exception):
                        self.listeners[provider].stop()
                    del self.listeners[provider]
                    LOGGER.critical("Listener for %s switched off: %s", provider, str(cause_of_death))

    def run(self):
        """Monitor the listeners."""
        try:
            while self.running:
                if self.listener_died_event.wait(LISTENER_CHECK_INTERVAL):
                    self.restart_dead_listeners()
                    self.listener_died_event.clear()
        except Exception:
            LOGGER.exception("Chain %s died!", self._name)

    def config_equals(self, other_config):
        """Check that current config is the same as `other_config`."""
        for key, val in other_config.items():
            if ((key not in ["listeners", "publisher"]) and
                ((key not in self._config) or
                    (self._config[key] != val))):
                return False
        return True

    def get_unchanged_providers(self, other_config):
        """Get a list of providers that have not changed between this and other config."""
        if self._config["topic"] != other_config["topic"]:
            return []
        return list(set(self._config["providers"]).intersection(set(other_config["providers"])))

    def publisher_needs_restarting(self, other_config):
        """Check that current config is the same as `other_config`."""
        for key in ["nameservers", "publish_port"]:
            if self._config[key] != other_config[key]:
                return True
        return False

    def refresh(self, new_config):
        """Refresh the chain with new config."""
        publisher_needs_restarting = self.publisher_needs_restarting(new_config)
        unchanged_providers = self.get_unchanged_providers(new_config)
        self._config = new_config
        if publisher_needs_restarting:
            self._refresh_publisher()
        self._refresh_listeners(unchanged_providers)
        if not self.running:
            self.start()

    def _refresh_publisher(self):
        self._stop_publisher()
        self.setup_publisher()

    def _refresh_listeners(self, unchanged_providers):
        self.reset_listeners(keep_providers=unchanged_providers)
        self.setup_listeners(keep_providers=unchanged_providers)

    def reset_listeners(self, keep_providers=None):
        """Reset the listeners."""
        keep_providers = keep_providers or []
        kept_listeners = {}
        for key, listener in self.listeners.items():
            if key in keep_providers:
                kept_listeners[key] = listener
                continue
            listener.stop()
        self.listeners = kept_listeners

    def stop(self):
        """Stop the chain."""
        self._stop_publisher()
        self.running = False
        self.reset_listeners()

    def _stop_publisher(self):
        if self.publisher:
            self._pub_starter.stop()
            self._pub_starter = None
            self.publisher = None

    def restart(self):
        """Restart the chain, return a new running instance."""
        self.stop()
        new_chain = self.__class__(self._name, self._config)
        new_chain.setup_listeners()
        new_chain.start()
        return new_chain


def reload_config(filename, chains):
    """Rebuild chains if needed (if the configuration changed) from *filename*."""
    LOGGER.debug("New config file detected: %s", filename)

    new_configs = read_config(filename)

    # setup new chains
    for key, new_config in new_configs.items():
        if key in chains:
            if chains[key].config_equals(new_config):
                continue
            verb = "Updated"
            LOGGER.debug("Updating %s", key)
        else:
            verb = "Added"
            LOGGER.debug("Adding %s", key)
            chains[key] = Chain(key, new_config)
            chains[key].start()

        chains[key].refresh(new_config)

        LOGGER.debug("%s %s", verb, key)

    # disable old chains

    for key in (set(chains.keys()) - set(new_configs.keys())):
        chains[key].stop()

        del chains[key]
        LOGGER.debug("Removed %s", key)

    LOGGER.debug("Reloaded config from %s", filename)


class PushRequester:
    """Base requester class."""

    request_retries = 3

    def __init__(self, host, port):
        """Initialize pish request."""
        self._socket = None
        self._reqaddress = "tcp://" + host + ":" + str(port)
        self._poller = Poller()
        self._lock = Lock()
        self.failures = 0
        self.jammed = False
        self.running = True

        self.connect()

    def connect(self):
        """Connect to the server."""
        self._socket = get_context().socket(REQ)
        self._socket.connect(self._reqaddress)
        self._poller.register(self._socket, POLLIN)

    def stop(self):
        """Close the connection to the server."""
        self.running = False
        self._socket.setsockopt(LINGER, 0)
        self._socket.close()
        self._poller.unregister(self._socket)

    def reset_connection(self):
        """Reset the socket."""
        self.stop()
        self.connect()

    def __del__(self, *args, **kwargs):
        """Stop the push requester when deleted."""
        self.stop()

    def send_and_recv(self, msg, timeout=DEFAULT_REQ_TIMEOUT):
        """Send a message and receive a response."""
        with self._lock:
            retries_left = self.request_retries
            request = str(msg)
            self._socket.send_string(request)
            rep = None
            small_timeout = 0.1
            while retries_left and self.running:
                now = time.time()
                while time.time() < now + timeout:
                    if not self.running:
                        return rep
                    socks = dict(self._poller.poll(small_timeout))
                    if socks.get(self._socket) == POLLIN:
                        reply = self._socket.recv()
                        if not reply:
                            LOGGER.error("Empty reply!")
                            break
                        try:
                            rep = Message(rawstr=reply)
                        except MessageError as err:
                            LOGGER.error('Message error: %s', str(err))
                            break
                        LOGGER.debug("Receiving (REQ) %s", str(rep))
                        self.failures = 0
                        self.jammed = False
                        return rep
                    # During big file transfers, give some time to a friend.
                    time.sleep(0.1)

                LOGGER.warning("Timeout from %s, retrying...",
                               str(self._reqaddress))
                # Socket is confused. Close and remove it.
                self.stop()
                retries_left -= 1
                if retries_left <= 0:
                    LOGGER.error("Server %s doesn't answer, abandoning.",
                                 str(self._reqaddress))
                    self.connect()
                    self.failures += 1
                    if self.failures == 5:
                        LOGGER.critical("Server jammed: %s", self._reqaddress)
                        self.jammed = True
                    break
                LOGGER.info("Reconnecting and resending %s", str(msg))
                # Create new connection
                self.connect()
                self._socket.send_string(request)

        return rep


def parse_args(args=None):
    """Parse commandline arguments."""
    parser = argparse.ArgumentParser()
    parser.add_argument("config_file",
                        help="The configuration file to run on.")
    add_logging_options_to_parser(parser, legacy=True)
    return parser.parse_args(args)


class MoveItClient(MoveItBase):
    """Trollmoves client class."""

    def __init__(self, cmd_args):
        """Initialize client."""
        self.name = "move_it_client"
        super().__init__(cmd_args)

    def reload_cfg_file(self, filename, *args, **kwargs):
        """Reload configuration file."""
        reload_config(filename, self.chains, *args, **kwargs)

    def signal_reload_cfg_file(self, *args):
        """Handle reload signal."""
        reload_config(self.cmd_args.config_file, self.chains,
                      publisher=self.publisher)

    def _run(self):
        for chain_name in self.chains:
            if not self.chains[chain_name].is_alive():
                self.chains[chain_name] = self.chains[chain_name].restart()
            self.chains[chain_name].publisher.heartbeat(30)

    def terminate(self):
        """Terminate client chains."""
        for chain in self.chains.values():
            chain.stop()
        LOGGER.info("Shutting down.")
        print("Thank you for using pytroll/move_it_client."
              " See you soon on pytroll.org!")