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path: root/policyhandler/policy_receiver.py
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# ================================================================================
# Copyright (c) 2018 AT&T Intellectual Property. All rights reserved.
# ================================================================================
# 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.
# ============LICENSE_END=========================================================
#
# ECOMP is a trademark and service mark of AT&T Intellectual Property.

"""
policy-receiver communicates with policy-engine
thru web-socket to receive push notifications
on updates and removal of policies.

on receiving the policy-notifications, the policy-receiver
passes the notifications to policy-updater
"""

import copy
import json
import logging
import os
import ssl
import time
from threading import Lock, Thread

import websocket

from .config import Config, Settings
from .policy_consts import MATCHING_CONDITIONS, POLICY_NAME, POLICY_VERSION
from .policy_updater import PolicyUpdater
from .policy_utils import Utils

LOADED_POLICIES = 'loadedPolicies'
REMOVED_POLICIES = 'removedPolicies'
POLICY_VER = 'versionNo'
POLICY_MATCHES = 'matches'

class _PolicyReceiver(Thread):
    """web-socket to PolicyEngine"""
    _logger = logging.getLogger("policy_handler.policy_receiver")

    def __init__(self):
        """web-socket inside the thread to receive policy notifications from PolicyEngine"""
        Thread.__init__(self, name="policy_receiver", daemon=True)

        self._lock = Lock()
        self._keep_running = True
        self._settings = Settings(Config.FIELD_POLICY_ENGINE)

        self._web_socket_url = None
        self._web_socket_sslopt = None
        self._tls_wss_ca_mode = None
        self._web_socket = None
        self.reconfigure()

        self._policy_updater = PolicyUpdater(self.reconfigure)
        self._policy_updater.start()

    def reconfigure(self):
        """configure and reconfigure the web-socket"""
        with self._lock:
            self._settings.set_config(Config.discovered_config)
            changed, config = self._settings.get_by_key(Config.FIELD_POLICY_ENGINE)

            if not changed:
                self._settings.commit_change()
                return False

            prev_web_socket_url = self._web_socket_url
            prev_web_socket_sslopt = self._web_socket_sslopt
            self._web_socket_sslopt = None

            resturl = (config.get("url", "").lower()
                       + config.get("path_notifications", "/pdp/notifications"))

            self._tls_wss_ca_mode = config.get(Config.TLS_WSS_CA_MODE)

            if resturl.startswith("https:"):
                self._web_socket_url = resturl.replace("https:", "wss:")

                verify = Config.get_tls_verify(self._tls_wss_ca_mode)
                if verify is False:
                    self._web_socket_sslopt = {'cert_reqs': ssl.CERT_NONE}
                elif verify is True:
                    pass
                else:
                    self._web_socket_sslopt = {'ca_certs': verify}

            else:
                self._web_socket_url = resturl.replace("http:", "ws:")

            if (self._web_socket_url == prev_web_socket_url
                    and Utils.are_the_same(prev_web_socket_sslopt, self._web_socket_sslopt)):
                _PolicyReceiver._logger.info(
                    "not changed web_socket_url(%s) or tls_wss_ca_mode(%s): %s",
                    self._web_socket_url, self._tls_wss_ca_mode, self._settings)
                self._settings.commit_change()
                return False

            _PolicyReceiver._logger.info("changed web_socket_url(%s) or tls_wss_ca_mode(%s): %s",
                                         self._web_socket_url, self._tls_wss_ca_mode,
                                         self._settings)
            self._settings.commit_change()

        self._stop_notifications()
        return True

    def run(self):
        """listen on web-socket and pass the policy notifications to policy-updater"""
        websocket.enableTrace(True)
        restarting = False
        while True:
            if not self._get_keep_running():
                break

            self._stop_notifications()

            if restarting:
                time.sleep(5)
                if not self._get_keep_running():
                    break

            with self._lock:
                web_socket_url = self._web_socket_url
                sslopt = copy.deepcopy(self._web_socket_sslopt)
                tls_wss_ca_mode = self._tls_wss_ca_mode

            _PolicyReceiver._logger.info(
                "connecting to policy-notifications at %s with sslopt(%s) tls_wss_ca_mode(%s)",
                web_socket_url, json.dumps(sslopt), tls_wss_ca_mode)

            self._web_socket = websocket.WebSocketApp(
                web_socket_url,
                on_message=self._on_pdp_message,
                on_close=self._on_ws_close,
                on_error=self._on_ws_error
            )

            _PolicyReceiver._logger.info("waiting for policy-notifications...")
            self._web_socket.run_forever(sslopt=sslopt)
            restarting = True

        _PolicyReceiver._logger.info("exit policy-receiver")

    def _get_keep_running(self):
        """thread-safe check whether to continue running"""
        with self._lock:
            keep_running = self._keep_running
        return keep_running

    def _stop_notifications(self):
        """close the web-socket == stops the notification service if running."""
        with self._lock:
            if self._web_socket and self._web_socket.sock and self._web_socket.sock.connected:
                self._web_socket.close()
                _PolicyReceiver._logger.info("Stopped receiving notifications from PDP")

    def _on_pdp_message(self, *args):
        """received the notification from PDP"""
        try:
            message = args and args[-1]
            _PolicyReceiver._logger.info("Received notification message: %s", message)
            if not message:
                return
            message = json.loads(message)

            if not message or not isinstance(message, dict):
                _PolicyReceiver._logger.warning("unexpected message from PDP: %s",
                                                json.dumps(message))
                return

            policies_updated = [
                {POLICY_NAME: policy.get(POLICY_NAME),
                 POLICY_VERSION: policy.get(POLICY_VER),
                 MATCHING_CONDITIONS: policy.get(POLICY_MATCHES, {})}
                for policy in message.get(LOADED_POLICIES, [])
            ]

            policies_removed = [
                {POLICY_NAME: removed_policy.get(POLICY_NAME),
                 POLICY_VERSION: removed_policy.get(POLICY_VER)}
                for removed_policy in message.get(REMOVED_POLICIES, [])
            ]

            if not policies_updated and not policies_removed:
                _PolicyReceiver._logger.info("no policy updated or removed")
                return

            self._policy_updater.policy_update(policies_updated, policies_removed)
        except Exception as ex:
            error_msg = "crash {} {} at {}: {}".format(type(ex).__name__, str(ex),
                                                       "on_pdp_message", json.dumps(message))

            _PolicyReceiver._logger.exception(error_msg)

    def _on_ws_error(self, error):
        """report an error"""
        _PolicyReceiver._logger.exception("policy-notification error: %s", str(error))

    def _on_ws_close(self, code, reason):
        """restart web-socket on close"""
        _PolicyReceiver._logger.info("lost connection(%s, %s) to PDP - restarting...", code, reason)

    def shutdown(self, audit):
        """Shutdown the policy-receiver"""
        _PolicyReceiver._logger.info("shutdown policy-receiver")
        with self._lock:
            self._keep_running = False

        self._stop_notifications()

        if self.is_alive():
            self.join()

        self._policy_updater.shutdown(audit)

    def catch_up(self, audit):
        """need to bring the latest policies to DCAE-Controller"""
        self._policy_updater.catch_up(audit)

class PolicyReceiver(object):
    """policy-receiver - static singleton wrapper"""
    _policy_receiver = None

    @staticmethod
    def shutdown(audit):
        """Shutdown the notification-handler"""
        PolicyReceiver._policy_receiver.shutdown(audit)

    @staticmethod
    def catch_up(audit):
        """bring the latest policies from policy-engine"""
        PolicyReceiver._policy_receiver.catch_up(audit)

    @staticmethod
    def run(audit):
        """Using policy-engine client to talk to policy engine"""
        PolicyReceiver._policy_receiver = _PolicyReceiver()
        PolicyReceiver._policy_receiver.start()

        PolicyReceiver.catch_up(audit)