# Microsoft Azure Linux Agent
#
# Copyright 2018 Microsoft Corporation
#
# 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.
#
# Requires Python 2.6+ and Openssl 1.0+

import json
import os
import random
import time
import uuid
import xml.sax.saxutils as saxutils
from collections import defaultdict
from datetime import datetime, timedelta

import azurelinuxagent.common.conf as conf
import azurelinuxagent.common.logger as logger
import azurelinuxagent.common.utils.textutil as textutil
from azurelinuxagent.common.agent_supported_feature import get_agent_supported_features_list_for_crp
from azurelinuxagent.common.datacontract import validate_param
from azurelinuxagent.common.event import add_event, WALAEventOperation, report_event, \
    CollectOrReportEventDebugInfo, add_periodic
from azurelinuxagent.common.exception import ProtocolNotFoundError, \
    ResourceGoneError, ExtensionDownloadError, InvalidContainerError, ProtocolError, HttpError
from azurelinuxagent.common.future import httpclient, bytebuffer, ustr
from azurelinuxagent.common.protocol.extensions_goal_state import ExtensionsGoalState
from azurelinuxagent.common.protocol.goal_state import GoalState, TRANSPORT_CERT_FILE_NAME, TRANSPORT_PRV_FILE_NAME
from azurelinuxagent.common.protocol.hostplugin import HostPluginProtocol
from azurelinuxagent.common.protocol.restapi import DataContract, ExtHandlerPackage, \
    ExtHandlerPackageList, ExtHandlerVersionUri, ProvisionStatus, VMInfo, VMStatus
from azurelinuxagent.common.telemetryevent import GuestAgentExtensionEventsSchema
from azurelinuxagent.common.utils import fileutil, restutil
from azurelinuxagent.common.utils.archive import StateFlusher
from azurelinuxagent.common.utils.cryptutil import CryptUtil
from azurelinuxagent.common.utils.textutil import parse_doc, findall, find, \
    findtext, gettext, remove_bom, get_bytes_from_pem, parse_json
from azurelinuxagent.common.version import AGENT_NAME, CURRENT_VERSION

VERSION_INFO_URI = "http://{0}/?comp=versions"
HEALTH_REPORT_URI = "http://{0}/machine?comp=health"
ROLE_PROP_URI = "http://{0}/machine?comp=roleProperties"
TELEMETRY_URI = "http://{0}/machine?comp=telemetrydata"

WIRE_SERVER_ADDR_FILE_NAME = "WireServer"
INCARNATION_FILE_NAME = "Incarnation"
GOAL_STATE_FILE_NAME = "GoalState.{0}.xml"
VM_SETTINGS_FILE_NAME = "VmSettings.{0}.json"
HOSTING_ENV_FILE_NAME = "HostingEnvironmentConfig.xml"
SHARED_CONF_FILE_NAME = "SharedConfig.xml"
REMOTE_ACCESS_FILE_NAME = "RemoteAccess.{0}.xml"
EXT_CONF_FILE_NAME = "ExtensionsConfig.{0}.xml"
MANIFEST_FILE_NAME = "{0}.{1}.manifest.xml"

PROTOCOL_VERSION = "2012-11-30"
ENDPOINT_FINE_NAME = "WireServer"

SHORT_WAITING_INTERVAL = 1  # 1 second

MAX_EVENT_BUFFER_SIZE = 2 ** 16 - 2 ** 10


class UploadError(HttpError):
    pass


class WireProtocol(DataContract):
    def __init__(self, endpoint):
        if endpoint is None:
            raise ProtocolError("WireProtocol endpoint is None")
        self.client = WireClient(endpoint)

    def detect(self):
        self.client.check_wire_protocol_version()

        trans_prv_file = os.path.join(conf.get_lib_dir(),
                                      TRANSPORT_PRV_FILE_NAME)
        trans_cert_file = os.path.join(conf.get_lib_dir(),
                                       TRANSPORT_CERT_FILE_NAME)
        cryptutil = CryptUtil(conf.get_openssl_cmd())
        cryptutil.gen_transport_cert(trans_prv_file, trans_cert_file)

        # Initialize the goal state, including all the inner properties
        logger.info('Initializing goal state during protocol detection')
        self.client.update_goal_state(force_update=True)

    def update_goal_state(self):
        self.client.update_goal_state()

    def update_host_plugin_from_goal_state(self):
        self.client.update_host_plugin_from_goal_state()

    def get_endpoint(self):
        return self.client.get_endpoint()

    def get_vminfo(self):
        goal_state = self.client.get_goal_state()
        hosting_env = self.client.get_hosting_env()

        vminfo = VMInfo()
        vminfo.subscriptionId = None
        vminfo.vmName = hosting_env.vm_name
        vminfo.tenantName = hosting_env.deployment_name
        vminfo.roleName = hosting_env.role_name
        vminfo.roleInstanceName = goal_state.role_instance_id
        return vminfo

    def get_certs(self):
        certificates = self.client.get_certs()
        return certificates.cert_list

    def get_incarnation(self):
        return self.client.get_goal_state().incarnation

    def get_in_vm_gs_metadata(self):
        return self.client.get_extensions_goal_state().in_vm_gs_metadata

    def get_required_features(self):
        return self.client.get_extensions_goal_state().get_required_features()

    def get_vmagent_manifests(self):
        goal_state = self.client.get_goal_state()
        ext_conf = self.client.get_extensions_goal_state()
        return ext_conf.vmagent_manifests, goal_state.incarnation

    def get_vmagent_pkgs(self, vmagent_manifest):
        goal_state = self.client.get_goal_state()
        ga_manifest = self.client.fetch_gafamily_manifest(vmagent_manifest, goal_state)
        valid_pkg_list = ga_manifest.pkg_list
        return valid_pkg_list

    def get_ext_handlers(self):
        logger.verbose("Get extension handler config")
        goal_state = self.client.get_goal_state()
        extensions_goal_state = self.client.get_extensions_goal_state()
        # In wire protocol, incarnation is equivalent to ETag
        return extensions_goal_state.ext_handlers, goal_state.incarnation

    def get_ext_handler_pkgs(self, ext_handler):
        logger.verbose("Get extension handler package")
        man = self.client.get_ext_manifest(ext_handler)
        return man.pkg_list

    def get_artifacts_profile(self):
        logger.verbose("Get In-VM Artifacts Profile")
        return self.client.get_artifacts_profile()

    def _download_ext_handler_pkg_through_host(self, uri, destination):
        host = self.client.get_host_plugin()
        uri, headers = host.get_artifact_request(uri, host.manifest_uri)
        success = self.client.stream(uri, destination, headers=headers, use_proxy=False, max_retry=1)
        return success

    def download_ext_handler_pkg(self, uri, destination, headers=None, use_proxy=True):  # pylint: disable=W0613
        direct_func = lambda: self.client.stream(uri, destination, headers=None, use_proxy=True, max_retry=1)
        # NOTE: the host_func may be called after refreshing the goal state, be careful about any goal state data
        # in the lambda.
        host_func = lambda: self._download_ext_handler_pkg_through_host(uri, destination)

        try:
            success = self.client.send_request_using_appropriate_channel(direct_func, host_func) is not None
        except Exception:
            success = False

        return success

    def report_provision_status(self, provision_status):
        validate_param("provision_status", provision_status, ProvisionStatus)

        if provision_status.status is not None:
            self.client.report_health(provision_status.status,
                                      provision_status.subStatus,
                                      provision_status.description)
        if provision_status.properties.certificateThumbprint is not None:
            thumbprint = provision_status.properties.certificateThumbprint
            self.client.report_role_prop(thumbprint)

    def report_vm_status(self, vm_status):
        validate_param("vm_status", vm_status, VMStatus)
        self.client.status_blob.set_vm_status(vm_status)
        self.client.upload_status_blob()

    def report_event(self, events_iterator):
        self.client.report_event(events_iterator)

    def upload_logs(self, logs):
        self.client.upload_logs(logs)

    def get_status_blob_data(self):
        return self.client.status_blob.data


def _build_role_properties(container_id, role_instance_id, thumbprint):
    xml = (u"<?xml version=\"1.0\" encoding=\"utf-8\"?>"
           u"<RoleProperties>"
           u"<Container>"
           u"<ContainerId>{0}</ContainerId>"
           u"<RoleInstances>"
           u"<RoleInstance>"
           u"<Id>{1}</Id>"
           u"<Properties>"
           u"<Property name=\"CertificateThumbprint\" value=\"{2}\" />"
           u"</Properties>"
           u"</RoleInstance>"
           u"</RoleInstances>"
           u"</Container>"
           u"</RoleProperties>"
           u"").format(container_id, role_instance_id, thumbprint)
    return xml


def _build_health_report(incarnation, container_id, role_instance_id,
                         status, substatus, description):
    # The max description that can be sent to WireServer is 4096 bytes.
    # Exceeding this max can result in a failure to report health.
    # To keep this simple, we will keep a 10% buffer and trim before
    # encoding the description.
    if description:
        max_chars_before_encoding = 3686
        len_before_trim = len(description)
        description = description[:max_chars_before_encoding]
        trimmed_char_count = len_before_trim - len(description)
        if trimmed_char_count > 0:
            logger.info(
                'Trimmed health report description by {0} characters'.format(
                    trimmed_char_count
                )
            )

        # Escape '&', '<' and '>'
        description = saxutils.escape(ustr(description))

    detail = u''
    if substatus is not None:
        substatus = saxutils.escape(ustr(substatus))
        detail = (u"<Details>"
                  u"<SubStatus>{0}</SubStatus>"
                  u"<Description>{1}</Description>"
                  u"</Details>").format(substatus, description)
    xml = (u"<?xml version=\"1.0\" encoding=\"utf-8\"?>"
           u"<Health "
           u"xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\""
           u" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\">"
           u"<GoalStateIncarnation>{0}</GoalStateIncarnation>"
           u"<Container>"
           u"<ContainerId>{1}</ContainerId>"
           u"<RoleInstanceList>"
           u"<Role>"
           u"<InstanceId>{2}</InstanceId>"
           u"<Health>"
           u"<State>{3}</State>"
           u"{4}"
           u"</Health>"
           u"</Role>"
           u"</RoleInstanceList>"
           u"</Container>"
           u"</Health>"
           u"").format(incarnation,
                       container_id,
                       role_instance_id,
                       status,
                       detail)
    return xml


def ga_status_to_guest_info(ga_status):
    """
    Convert VMStatus object to status blob format
    """
    v1_ga_guest_info = {
        "computerName": ga_status.hostname,
        "osName": ga_status.osname,
        "osVersion": ga_status.osversion,
        "version": ga_status.version,
    }
    return v1_ga_guest_info


def __get_formatted_msg_for_status_reporting(msg, lang="en-US"):
    return {
        'lang': lang,
        'message': msg
    }


def _get_utc_timestamp_for_status_reporting(time_format="%Y-%m-%dT%H:%M:%SZ", timestamp=None):
    timestamp = time.gmtime() if timestamp is None else timestamp
    return time.strftime(time_format, timestamp)


def ga_status_to_v1(ga_status):
    v1_ga_status = {
        "version": ga_status.version,
        "status": ga_status.status,
        "formattedMessage": __get_formatted_msg_for_status_reporting(ga_status.message)
    }
    return v1_ga_status


def ext_substatus_to_v1(sub_status_list):
    status_list = []
    for substatus in sub_status_list:
        status = {
            "name": substatus.name,
            "status": substatus.status,
            "code": substatus.code,
            "formattedMessage": __get_formatted_msg_for_status_reporting(substatus.message)
        }
        status_list.append(status)
    return status_list


def ext_status_to_v1(ext_status):
    if ext_status is None:
        return None
    timestamp = _get_utc_timestamp_for_status_reporting()
    v1_sub_status = ext_substatus_to_v1(ext_status.substatusList)
    v1_ext_status = {
        "status": {
            "name": ext_status.name,
            "configurationAppliedTime": ext_status.configurationAppliedTime,
            "operation": ext_status.operation,
            "status": ext_status.status,
            "code": ext_status.code,
            "formattedMessage": __get_formatted_msg_for_status_reporting(ext_status.message)
        },
        "version": 1.0,
        "timestampUTC": timestamp
    }
    if len(v1_sub_status) != 0:
        v1_ext_status['status']['substatus'] = v1_sub_status
    return v1_ext_status


def ext_handler_status_to_v1(ext_handler_status):
    v1_handler_status = {
        'handlerVersion': ext_handler_status.version,
        'handlerName': ext_handler_status.name,
        'status': ext_handler_status.status,
        'code': ext_handler_status.code,
        'useExactVersion': True
    }
    if ext_handler_status.message is not None:
        v1_handler_status["formattedMessage"] = __get_formatted_msg_for_status_reporting(ext_handler_status.message)

    v1_ext_status = ext_status_to_v1(ext_handler_status.extension_status)
    if ext_handler_status.extension_status is not None and v1_ext_status is not None:
        v1_handler_status["runtimeSettingsStatus"] = {
            'settingsStatus': v1_ext_status,
            'sequenceNumber': ext_handler_status.extension_status.sequenceNumber
        }

        # Add extension name if Handler supports MultiConfig
        if ext_handler_status.supports_multi_config:
            v1_handler_status["runtimeSettingsStatus"]["extensionName"] = ext_handler_status.extension_status.name

    return v1_handler_status


def vm_artifacts_aggregate_status_to_v1(vm_artifacts_aggregate_status):
    gs_aggregate_status = vm_artifacts_aggregate_status.goal_state_aggregate_status
    if gs_aggregate_status is None:
        return None

    v1_goal_state_aggregate_status = {
        "formattedMessage": __get_formatted_msg_for_status_reporting(gs_aggregate_status.message),
        "timestampUTC": _get_utc_timestamp_for_status_reporting(timestamp=gs_aggregate_status.processed_time),
        "inSvdSeqNo": gs_aggregate_status.in_svd_seq_no,
        "status": gs_aggregate_status.status,
        "code": gs_aggregate_status.code
    }

    v1_artifact_aggregate_status = {
        "goalStateAggregateStatus": v1_goal_state_aggregate_status
    }
    return v1_artifact_aggregate_status


def vm_status_to_v1(vm_status):
    timestamp = _get_utc_timestamp_for_status_reporting()

    v1_ga_guest_info = ga_status_to_guest_info(vm_status.vmAgent)
    v1_ga_status = ga_status_to_v1(vm_status.vmAgent)
    v1_vm_artifact_aggregate_status = vm_artifacts_aggregate_status_to_v1(
        vm_status.vmAgent.vm_artifacts_aggregate_status)
    v1_handler_status_list = []
    for handler_status in vm_status.vmAgent.extensionHandlers:
        v1_handler_status_list.append(ext_handler_status_to_v1(handler_status))

    v1_agg_status = {
        'guestAgentStatus': v1_ga_status,
        'handlerAggregateStatus': v1_handler_status_list
    }

    if v1_vm_artifact_aggregate_status is not None:
        v1_agg_status['vmArtifactsAggregateStatus'] = v1_vm_artifact_aggregate_status

    v1_vm_status = {
        'version': '1.1',
        'timestampUTC': timestamp,
        'aggregateStatus': v1_agg_status,
        'guestOSInfo': v1_ga_guest_info
    }

    supported_features = []
    for _, feature in get_agent_supported_features_list_for_crp().items():
        supported_features.append(
            {
                "Key": feature.name,
                "Value": feature.version
            }
        )
    if supported_features:
        v1_vm_status["supportedFeatures"] = supported_features

    return v1_vm_status


class StatusBlob(object):
    def __init__(self, client):
        self.vm_status = None
        self.client = client
        self.type = None
        self.data = None

    def set_vm_status(self, vm_status):
        validate_param("vmAgent", vm_status, VMStatus)
        self.vm_status = vm_status

    def to_json(self):
        report = vm_status_to_v1(self.vm_status)
        return json.dumps(report)

    __storage_version__ = "2014-02-14"

    def prepare(self, blob_type):
        logger.verbose("Prepare status blob")
        self.data = self.to_json()
        self.type = blob_type

    def upload(self, url):
        try:
            if not self.type in ["BlockBlob", "PageBlob"]:
                raise ProtocolError("Illegal blob type: {0}".format(self.type))

            if self.type == "BlockBlob":
                self.put_block_blob(url, self.data)
            else:
                self.put_page_blob(url, self.data)
            return True

        except Exception as e:
            logger.verbose("Initial status upload failed: {0}", e)

        return False

    def get_block_blob_headers(self, blob_size):
        return {
            "Content-Length": ustr(blob_size),
            "x-ms-blob-type": "BlockBlob",
            "x-ms-date": _get_utc_timestamp_for_status_reporting(),
            "x-ms-version": self.__class__.__storage_version__
        }

    def put_block_blob(self, url, data):
        logger.verbose("Put block blob")
        headers = self.get_block_blob_headers(len(data))
        resp = self.client.call_storage_service(restutil.http_put, url, data, headers)
        if resp.status != httpclient.CREATED:
            raise UploadError(
                "Failed to upload block blob: {0}".format(resp.status))

    def get_page_blob_create_headers(self, blob_size):
        return {
            "Content-Length": "0",
            "x-ms-blob-content-length": ustr(blob_size),
            "x-ms-blob-type": "PageBlob",
            "x-ms-date": _get_utc_timestamp_for_status_reporting(),
            "x-ms-version": self.__class__.__storage_version__
        }

    def get_page_blob_page_headers(self, start, end):
        return {
            "Content-Length": ustr(end - start),
            "x-ms-date": _get_utc_timestamp_for_status_reporting(),
            "x-ms-range": "bytes={0}-{1}".format(start, end - 1),
            "x-ms-page-write": "update",
            "x-ms-version": self.__class__.__storage_version__
        }

    def put_page_blob(self, url, data):
        logger.verbose("Put page blob")

        # Convert string into bytes and align to 512 bytes
        data = bytearray(data, encoding='utf-8')
        page_blob_size = int((len(data) + 511) / 512) * 512

        headers = self.get_page_blob_create_headers(page_blob_size)
        resp = self.client.call_storage_service(restutil.http_put, url, "", headers)
        if resp.status != httpclient.CREATED:
            raise UploadError(
                "Failed to clean up page blob: {0}".format(resp.status))

        if url.count("?") <= 0:
            url = "{0}?comp=page".format(url)
        else:
            url = "{0}&comp=page".format(url)

        logger.verbose("Upload page blob")
        page_max = 4 * 1024 * 1024  # Max page size: 4MB
        start = 0
        end = 0
        while end < len(data):
            end = min(len(data), start + page_max)
            content_size = end - start
            # Align to 512 bytes
            page_end = int((end + 511) / 512) * 512
            buf_size = page_end - start
            buf = bytearray(buf_size)
            buf[0: content_size] = data[start: end]
            headers = self.get_page_blob_page_headers(start, page_end)
            resp = self.client.call_storage_service(
                restutil.http_put,
                url,
                bytebuffer(buf),
                headers)
            if resp is None or resp.status != httpclient.CREATED:
                raise UploadError(
                    "Failed to upload page blob: {0}".format(resp.status))
            start = end


def event_param_to_v1(param):
    param_format = ustr('<Param Name="{0}" Value={1} T="{2}" />')
    param_type = type(param.value)
    attr_type = ""
    if param_type is int:
        attr_type = 'mt:uint64'
    elif param_type is str:
        attr_type = 'mt:wstr'
    elif ustr(param_type).count("'unicode'") > 0:
        attr_type = 'mt:wstr'
    elif param_type is bool:
        attr_type = 'mt:bool'
    elif param_type is float:
        attr_type = 'mt:float64'
    return param_format.format(param.name,
                               saxutils.quoteattr(ustr(param.value)),
                               attr_type)


def event_to_v1_encoded(event, encoding='utf-8'):
    params = ""
    for param in event.parameters:
        params += event_param_to_v1(param)
    event_str = ustr('<Event id="{0}"><![CDATA[{1}]]></Event>').format(event.eventId, params)
    return event_str.encode(encoding)


class WireClient(object):

    def __init__(self, endpoint):
        logger.info("Wire server endpoint:{0}", endpoint)
        self._endpoint = endpoint
        self._goal_state = None
        self._extensions_goal_state = None  # goal state from ExtensionsConfig
        self._extensions_goal_state_from_vm_settings = None  # goal state from vmSettings
        self._host_plugin = None
        self.status_blob = StatusBlob(self)
        self.goal_state_flusher = StateFlusher(conf.get_lib_dir())
        self._vm_settings_error_reporter = _ErrorReporter(WALAEventOperation.VmSettings)

    def get_endpoint(self):
        return self._endpoint

    def call_wireserver(self, http_req, *args, **kwargs):
        try:
            # Never use the HTTP proxy for wireserver
            kwargs['use_proxy'] = False
            resp = http_req(*args, **kwargs)

            if restutil.request_failed(resp):
                msg = "[Wireserver Failed] URI {0} ".format(args[0])
                if resp is not None:
                    msg += " [HTTP Failed] Status Code {0}".format(resp.status)
                raise ProtocolError(msg)

        # If the GoalState is stale, pass along the exception to the caller
        except ResourceGoneError:
            raise

        except Exception as e:
            raise ProtocolError("[Wireserver Exception] {0}".format(
                ustr(e)))

        return resp

    def decode_config(self, data):
        if data is None:
            return None
        data = remove_bom(data)
        xml_text = ustr(data, encoding='utf-8')
        return xml_text

    def fetch_config(self, uri, headers):
        resp = self.call_wireserver(restutil.http_get,
                                    uri,
                                    headers=headers)
        return self.decode_config(resp.read())

    def fetch_cache(self, local_file):
        if not os.path.isfile(local_file):
            raise ProtocolError("{0} is missing.".format(local_file))
        try:
            return fileutil.read_file(local_file)
        except IOError as e:
            raise ProtocolError("Failed to read cache: {0}".format(e))

    @staticmethod
    def _save_cache(data, file_name):
        try:
            file_path = os.path.join(conf.get_lib_dir(), file_name)
            fileutil.write_file(file_path, data)
        except IOError as e:
            fileutil.clean_ioerror(e, paths=[file_name])
            raise ProtocolError("Failed to write cache: {0}".format(e))

    @staticmethod
    def call_storage_service(http_req, *args, **kwargs):
        # Default to use the configured HTTP proxy
        if not 'use_proxy' in kwargs or kwargs['use_proxy'] is None:
            kwargs['use_proxy'] = True

        return http_req(*args, **kwargs)

    def fetch_manifest_through_host(self, uri):
        host = self.get_host_plugin()
        uri, headers = host.get_artifact_request(uri)
        response, _ = self.fetch(uri, headers, use_proxy=False, max_retry=1)
        return response

    def fetch_manifest(self, version_uris, timeout_in_minutes=5, timeout_in_ms=0):
        logger.verbose("Fetch manifest")
        version_uris_shuffled = version_uris
        random.shuffle(version_uris_shuffled)

        uris_tried = 0
        start_time = datetime.now()
        for version in version_uris_shuffled:

            if datetime.now() - start_time > timedelta(minutes=timeout_in_minutes, milliseconds=timeout_in_ms):
                logger.warn("Agent timed-out after {0} minutes while fetching extension manifests. {1}/{2} uris tried.",
                    timeout_in_minutes, uris_tried, len(version_uris))
                break

            # GA expects a location and failoverLocation in ExtensionsConfig, but
            # this is not always the case. See #1147.
            if version.uri is None:
                logger.verbose('The specified manifest URL is empty, ignored.')
                continue

            direct_func = lambda: self.fetch(version.uri, max_retry=1)[0]  # pylint: disable=W0640
            # NOTE: the host_func may be called after refreshing the goal state, be careful about any goal state data
            # in the lambda.
            host_func = lambda: self.fetch_manifest_through_host(version.uri)  # pylint: disable=W0640

            try:
                manifest = self.send_request_using_appropriate_channel(direct_func, host_func)
                if manifest is not None:
                    host = self.get_host_plugin()
                    host.update_manifest_uri(version.uri)
                    return manifest
            except Exception as error:
                logger.warn("Failed to fetch manifest from {0}. Error: {1}", version.uri, ustr(error))

            uris_tried += 1

        raise ExtensionDownloadError("Failed to fetch manifest from all sources")

    def stream(self, uri, destination, headers=None, use_proxy=None, max_retry=None):
        """
        max_retry indicates the maximum number of retries for the HTTP request; None indicates that the default value should be used
        """
        success = False
        logger.verbose("Fetch [{0}] with headers [{1}] to file [{2}]", uri, headers, destination)

        response = self._fetch_response(uri, headers, use_proxy,  max_retry=max_retry)
        if response is not None and not restutil.request_failed(response):
            chunk_size = 1024 * 1024  # 1MB buffer
            try:
                with open(destination, 'wb', chunk_size) as destination_fh:
                    complete = False
                    while not complete:
                        chunk = response.read(chunk_size)
                        destination_fh.write(chunk)
                        complete = len(chunk) < chunk_size
                success = True
            except Exception as error:
                logger.error('Error streaming {0} to {1}: {2}'.format(uri, destination, ustr(error)))

        return success

    def fetch(self, uri, headers=None, use_proxy=None, decode=True, max_retry=None, ok_codes=None):
        """
        max_retry indicates the maximum number of retries for the HTTP request; None indicates that the default value should be used

        Returns a tuple with the content and headers of the response. The headers are a list of (name, value) tuples.
        """
        logger.verbose("Fetch [{0}] with headers [{1}]", uri, headers)
        content = None
        response = self._fetch_response(uri, headers, use_proxy, max_retry=max_retry, ok_codes=ok_codes)
        if response is not None and not restutil.request_failed(response, ok_codes=ok_codes):
            response_content = response.read()
            content = self.decode_config(response_content) if decode else response_content
        return content, response.getheaders()

    def _fetch_response(self, uri, headers=None, use_proxy=None, max_retry=None, ok_codes=None):
        """
        max_retry indicates the maximum number of retries for the HTTP request; None indicates that the default value should be used
        """
        resp = None
        try:
            resp = self.call_storage_service(
                restutil.http_get,
                uri,
                headers=headers,
                use_proxy=use_proxy,
                max_retry=max_retry)

            host_plugin = self.get_host_plugin()

            if restutil.request_failed(resp, ok_codes=ok_codes):
                error_response = restutil.read_response_error(resp)
                msg = "Fetch failed from [{0}]: {1}".format(uri, error_response)
                logger.warn(msg)

                if host_plugin is not None:
                    host_plugin.report_fetch_health(uri,
                                                    is_healthy=not restutil.request_failed_at_hostplugin(resp),
                                                    source='WireClient',
                                                    response=error_response)
                raise ProtocolError(msg)
            else:
                if host_plugin is not None:
                    host_plugin.report_fetch_health(uri, source='WireClient')

        except (HttpError, ProtocolError, IOError) as error:
            msg = "Fetch failed: {0}".format(error)
            logger.warn(msg)
            report_event(op=WALAEventOperation.HttpGet, is_success=False, message=msg, log_event=False)

            if isinstance(error, (InvalidContainerError, ResourceGoneError)):
                # These are retryable errors that should force a goal state refresh in the host plugin
                raise

        return resp

    def update_host_plugin_from_goal_state(self):
        """
        Fetches a new goal state and updates the Container ID and Role Config Name of the host plugin client
        """
        goal_state = GoalState(self)
        self._update_host_plugin(goal_state.container_id, goal_state.role_config_name)

    def update_goal_state(self, force_update=False):
        """
        Updates the goal state if the incarnation or etag changed or if 'force_update' is True
        """
        try:
            updated = False

            goal_state = GoalState(self)

            # Always update the hostgaplugin, since the agent may issue requests to it even if there are no other changes
            # in the goal state (e.g. report status)
            self._update_host_plugin(goal_state.container_id, goal_state.role_config_name)

            if force_update:
                logger.info("Forcing an update of the goal state..")

            fetch_full_goal_state = force_update or \
                self._goal_state is None or self._extensions_goal_state is None or \
                self._goal_state.incarnation != goal_state.incarnation

            #
            # TODO: Today we always update self._extensions_goal_state using the ExtensionsConfig. After that, (unless
            #       FastTrack is disabled in waagent.conf) we query the vmSettings only to compare them against the
            #       ExtensionsConfig.
            #       When FastTrack is fully implemented, we will need instead to update self._extensions_goal_state
            #       from the vmSettings and fallback to the ExtensionsConfig only if FastTrack is disabled or if it is
            #       not supported by the HostGAPlugin.
            #       Extensions processing is always based on self._extensions_goal_state, while self._extensions_goal_state_from_vm_settings
            #       is currently held only for debugging purposes.
            #
            if fetch_full_goal_state:
                goal_state.fetch_full_goal_state(self)
                self._goal_state = goal_state
                if self._goal_state.extensions_config_uri is None:
                    self._extensions_goal_state = ExtensionsGoalState.create_empty()
                else:
                    xml_text = self.fetch_config(self._goal_state.extensions_config_uri, self.get_header())
                    self._extensions_goal_state = ExtensionsGoalState.create_from_extensions_config(goal_state.incarnation, xml_text)
                updated = True

            if conf.get_enable_fast_track():
                # Since currently we query vmSettings only to exercise the HostGAPlugin, errors in this section of the code should not
                # prevent the agent from processing the goal state; we simply report a summary of those errors.
                try:
                    request_etag = None if force_update or self._extensions_goal_state_from_vm_settings is None else self._extensions_goal_state_from_vm_settings.get_id()
                    response_etag, vm_settings = self._fetch_vm_settings(request_etag)
                    if vm_settings is not None:  # vmSettings is None when there has not been a new goal state, or the HostGAPlugin does not support FastTrack
                        self._extensions_goal_state_from_vm_settings = ExtensionsGoalState.create_from_vm_settings(response_etag, vm_settings)
                        updated = True
                    # If either goal state was updated, compare them
                    if updated and self._extensions_goal_state_from_vm_settings is not None:
                        ExtensionsGoalState.compare(self._extensions_goal_state, self._extensions_goal_state_from_vm_settings)
                except Exception as error:
                    # TODO: Once FastTrack is stable, these exceptions should be rare. Add a traceback to the error message at that point.
                    self._vm_settings_error_reporter.report_error(ustr(error))
                self._vm_settings_error_reporter.report_summary()

            # If either goal state was updated, save them
            if updated:
                self._save_goal_state()

        except Exception as exception:
            raise ProtocolError("Error fetching goal state: {0}".format(ustr(exception)))

    def _fetch_vm_settings(self, etag):
        """
        Queries the vmSettings from the HostGAPlugin using the given etag, returns a tuple of the response's etag and content.
        If the vmSettings have not been updated for the given etag, or if the HostGAPlugin does not support FastTrack,
        returns (None, None).
        """
        correlation_id = str(uuid.uuid4())

        try:
            def get_vm_settings():
                url, headers = self.get_host_plugin().get_vm_settings_request(correlation_id)
                if etag is not None:
                    headers['if-none-match'] = etag
                return restutil.http_get(url, headers=headers, use_proxy=False, max_retry=1)

            try:
                response = get_vm_settings()
            except ResourceGoneError:  # retry after refreshing the HostGAPlugin
                self.update_host_plugin_from_goal_state()
                response = get_vm_settings()

            if response.status == httpclient.NOT_MODIFIED:
                return None, None

            # TODO: Currently we use the vmSettings just to compare against ExtensionsConfig and we handle
            #       Not Supported just as if there was no update in the vmSettings. Once FastTrack is
            #       fully enabled, if the HostGAPlugin does not support FastTrack we actually need to
            #       fallback to using the ExtensionsConfig
            if response.status == httpclient.NOT_FOUND:  # the HostGAPlugin does not support FastTrack
                return None, None
            # END TODO

            if response.status != httpclient.OK:
                error_description = restutil.read_response_error(response)
                # For historical reasons the HostGAPlugin returns 502 (BAD_GATEWAY) for internal errors instead of using
                # 500 (INTERNAL_SERVER_ERROR). We add a short prefix to the error message in the hope that it will help
                # clear any confusion produced by the poor choice of status code.
                if response.status == httpclient.BAD_GATEWAY:
                    error_description = "[Internal error in HostGAPlugin] {0}".format(error_description)
                raise ProtocolError("GET vmSettings [correlation ID: {0}]: {1} ({2})".format(correlation_id, response.status, error_description))

            for h in response.getheaders():
                if h[0].lower() == 'etag':
                    response_etag = h[1]
                    break
            else:  # since the vmSettings were updated, the response must include an etag
                raise ProtocolError("The vmSettings do no include an Etag [correlation ID: {0}]".format(correlation_id))

            logger.info("Fetched new vmSettings [correlation ID: {0} New eTag: {1}]", correlation_id, response_etag)
            response_content = self.decode_config(response.read())
            return response_etag, response_content

        except ProtocolError:
            raise
        except HttpError as http_error:
            raise Exception("{0} [correlation ID: {1} eTag: {2}]".format(ustr(http_error), correlation_id, etag))
        except Exception as exception:
            error = textutil.format_exception(exception)  # since this is a generic error, we format the exception to include the traceback
            raise Exception("Error fetching vmSettings [correlation ID: {0} eTag: {1}]: {2}".format(correlation_id, etag, error))

    def _update_host_plugin(self, container_id, role_config_name):
        if self._host_plugin is not None:
            self._host_plugin.update_container_id(container_id)
            self._host_plugin.update_role_config_name(role_config_name)

    def _save_goal_state(self):
        try:
            self.goal_state_flusher.flush()
        except Exception as e:
            logger.warn("Failed to save the previous goal state to the history folder: {0}", ustr(e))

        try:
            def save_if_not_none(goal_state_property, file_name):
                if goal_state_property is not None and goal_state_property.xml_text is not None:
                    self._save_cache(goal_state_property.xml_text, file_name)

            # NOTE: Certificates are saved in Certificate.__init__
            self._save_cache(self._goal_state.incarnation, INCARNATION_FILE_NAME)
            save_if_not_none(self._goal_state, GOAL_STATE_FILE_NAME.format(self._goal_state.incarnation))
            save_if_not_none(self._goal_state.hosting_env, HOSTING_ENV_FILE_NAME)
            save_if_not_none(self._goal_state.shared_conf, SHARED_CONF_FILE_NAME)
            save_if_not_none(self._goal_state.remote_access, REMOTE_ACCESS_FILE_NAME.format(self._goal_state.incarnation))
            if self._extensions_goal_state is not None:
                # disable=assignment-from-none: E1128: Assigning result of a function call, where the function returns None
                text = self._extensions_goal_state.get_redacted_text()  # pylint: disable=assignment-from-none
                if text != '':
                    self._save_cache(text, EXT_CONF_FILE_NAME.format(self._extensions_goal_state.get_id()))
            # TODO: When Fast Track is fully enabled self._extensions_goal_state_from_vm_settings will go away and this can be deleted
            if self._extensions_goal_state_from_vm_settings is not None:
                # disable=assignment-from-none: E1128: Assigning result of a function call, where the function returns None
                text = self._extensions_goal_state_from_vm_settings.get_redacted_text()  # pylint: disable=assignment-from-none
                if text != '':
                    self._save_cache(text, VM_SETTINGS_FILE_NAME.format(self._extensions_goal_state_from_vm_settings.get_id()))
            # END TODO

        except Exception as e:
            logger.warn("Failed to save the goal state to disk: {0}", ustr(e))

    def _set_host_plugin(self, new_host_plugin):
        if new_host_plugin is None:
            logger.warn("Setting empty Host Plugin object!")
        self._host_plugin = new_host_plugin

    def get_goal_state(self):
        if self._goal_state is None:
            raise ProtocolError("Trying to fetch goal state before initialization!")
        return self._goal_state

    def get_hosting_env(self):
        if self._goal_state is None:
            raise ProtocolError("Trying to fetch Hosting Environment before initialization!")
        return self._goal_state.hosting_env

    def get_shared_conf(self):
        if self._goal_state is None:
            raise ProtocolError("Trying to fetch Shared Conf before initialization!")
        return self._goal_state.shared_conf

    def get_certs(self):
        if self._goal_state is None:
            raise ProtocolError("Trying to fetch Certificates before initialization!")
        return self._goal_state.certs

    def get_extensions_goal_state(self):
        if self._extensions_goal_state is None:
            raise ProtocolError("Trying to fetch ExtensioalState before initialization!")
        return self._extensions_goal_state

    def get_ext_manifest(self, ext_handler):
        if self._goal_state is None:
            raise ProtocolError("Trying to fetch Extension Manifest before initialization!")

        try:
            xml_text = self.fetch_manifest(ext_handler.versionUris)
            self._save_cache(xml_text, MANIFEST_FILE_NAME.format(ext_handler.name, self.get_goal_state().incarnation))
            return ExtensionManifest(xml_text)
        except Exception as e:
            raise ExtensionDownloadError("Failed to retrieve extension manifest. Error: {0}".format(ustr(e)))

    def get_remote_access(self):
        if self._goal_state is None:
            raise ProtocolError("Trying to fetch Remote Access before initialization!")
        return self._goal_state.remote_access

    def fetch_gafamily_manifest(self, vmagent_manifest, goal_state):
        local_file = MANIFEST_FILE_NAME.format(vmagent_manifest.family, goal_state.incarnation)
        local_file = os.path.join(conf.get_lib_dir(), local_file)

        try:
            xml_text = self.fetch_manifest(vmagent_manifest.versionsManifestUris)
            fileutil.write_file(local_file, xml_text)
            return ExtensionManifest(xml_text)
        except Exception as e:
            raise ProtocolError("Failed to retrieve GAFamily manifest. Error: {0}".format(ustr(e)))

    def check_wire_protocol_version(self):
        uri = VERSION_INFO_URI.format(self.get_endpoint())
        version_info_xml = self.fetch_config(uri, None)
        version_info = VersionInfo(version_info_xml)

        preferred = version_info.get_preferred()
        if PROTOCOL_VERSION == preferred:
            logger.info("Wire protocol version:{0}", PROTOCOL_VERSION)
        elif PROTOCOL_VERSION in version_info.get_supported():
            logger.info("Wire protocol version:{0}", PROTOCOL_VERSION)
            logger.info("Server preferred version:{0}", preferred)
        else:
            error = ("Agent supported wire protocol version: {0} was not "
                     "advised by Fabric.").format(PROTOCOL_VERSION)
            raise ProtocolNotFoundError(error)

    def _call_hostplugin_with_container_check(self, host_func):
        """
        Calls host_func on host channel and accounts for stale resource (ResourceGoneError or InvalidContainerError).
        If stale, it refreshes the goal state and retries host_func.
        This method can throw, so the callers need to handle that.
        """
        try:
            ret = host_func()
            if ret in (None, False):
                raise Exception("Request failed using the host channel.")

            return ret
        except (ResourceGoneError, InvalidContainerError) as error:
            host_plugin = self.get_host_plugin()

            old_container_id, old_role_config_name = host_plugin.container_id, host_plugin.role_config_name
            msg = "[PERIODIC] Request failed with the current host plugin configuration. " \
                  "ContainerId: {0}, role config file: {1}. Fetching new goal state and retrying the call." \
                  "Error: {2}".format(old_container_id, old_role_config_name, ustr(error))
            logger.periodic_info(logger.EVERY_SIX_HOURS, msg)

            self.update_host_plugin_from_goal_state()

            new_container_id, new_role_config_name = host_plugin.container_id, host_plugin.role_config_name
            msg = "[PERIODIC] Host plugin reconfigured with new parameters. " \
                  "ContainerId: {0}, role config file: {1}.".format(new_container_id, new_role_config_name)
            logger.periodic_info(logger.EVERY_SIX_HOURS, msg)

            try:
                ret = host_func()

                if ret in (None, False):
                    raise Exception("Request failed using the host channel after goal state refresh.")

                msg = "[PERIODIC] Request succeeded using the host plugin channel after goal state refresh. " \
                      "ContainerId changed from {0} to {1}, " \
                      "role config file changed from {2} to {3}.".format(old_container_id, new_container_id,
                                                                         old_role_config_name, new_role_config_name)
                add_periodic(delta=logger.EVERY_SIX_HOURS,
                             name=AGENT_NAME,
                             version=CURRENT_VERSION,
                             op=WALAEventOperation.HostPlugin,
                             is_success=True,
                             message=msg,
                             log_event=True)
                return ret
            except (ResourceGoneError, InvalidContainerError) as error:
                msg = "[PERIODIC] Request failed using the host plugin channel after goal state refresh. " \
                      "ContainerId changed from {0} to {1}, role config file changed from {2} to {3}. " \
                      "Exception type: {4}.".format(old_container_id, new_container_id, old_role_config_name,
                                                    new_role_config_name, type(error).__name__)
                add_periodic(delta=logger.EVERY_SIX_HOURS,
                             name=AGENT_NAME,
                             version=CURRENT_VERSION,
                             op=WALAEventOperation.HostPlugin,
                             is_success=False,
                             message=msg,
                             log_event=True)
                raise

    def __send_request_using_host_channel(self, host_func):
        """
        Calls the host_func on host channel with retries for stale goal state and handles any exceptions, consistent with the caller for direct channel.
        At the time of writing, host_func internally calls either:
        1) WireClient.stream which returns a boolean, or
        2) WireClient.fetch which returns None or a HTTP response.
        This method returns either None (failure case where host_func returned None or False), True or an HTTP response.
        """
        ret = None
        try:
            ret = self._call_hostplugin_with_container_check(host_func)
        except Exception as error:
            logger.periodic_info(logger.EVERY_HOUR, "[PERIODIC] Request failed using the host channel. Error: {0}".format(ustr(error)))

        return ret

    @staticmethod
    def __send_request_using_direct_channel(direct_func):
        """
        Calls the direct_func on direct channel and handles any exceptions, consistent with the caller for host channel.
        At the time of writing, direct_func internally calls either:
        1) WireClient.stream which returns a boolean, or
        2) WireClient.fetch which returns None or a HTTP response.
        This method returns either None (failure case where direct_func returned None or False), True or an HTTP response.
        """
        ret = None
        try:
            ret = direct_func()

            if ret in (None, False):
                logger.periodic_info(logger.EVERY_HOUR, "[PERIODIC] Request failed using the direct channel.")
                return None
        except Exception as error:
            logger.periodic_info(logger.EVERY_HOUR, "[PERIODIC] Request failed using the direct channel. Error: {0}".format(ustr(error)))

        return ret

    def send_request_using_appropriate_channel(self, direct_func, host_func):
        """
        Determines which communication channel to use. By default, the primary channel is direct, host channel is secondary.
        We call the primary channel first and return on success. If primary fails, we try secondary. If secondary fails,
        we return and *don't* switch the default channel. If secondary succeeds, we change the default channel.
        This method doesn't raise since the calls to direct_func and host_func are already wrapped and handle any exceptions.
        Possible return values are manifest, artifacts profile, True or None.
        """
        direct_channel = lambda: self.__send_request_using_direct_channel(direct_func)
        host_channel = lambda: self.__send_request_using_host_channel(host_func)

        if HostPluginProtocol.is_default_channel:
            primary_channel, secondary_channel = host_channel, direct_channel
        else:
            primary_channel, secondary_channel = direct_channel, host_channel

        ret = primary_channel()
        if ret is not None:
            return ret

        ret = secondary_channel()
        if ret is not None:
            HostPluginProtocol.is_default_channel = not HostPluginProtocol.is_default_channel
            message = "Default channel changed to {0} channel.".format("HostGA" if HostPluginProtocol.is_default_channel else "direct")
            logger.info(message)
            add_event(AGENT_NAME, op=WALAEventOperation.DefaultChannelChange, version=CURRENT_VERSION, is_success=True, message=message, log_event=False)
        return ret

    def upload_status_blob(self):
        extensions_goal_state = self.get_extensions_goal_state()

        if extensions_goal_state.get_status_upload_blob() is None:
            # the status upload blob is in ExtensionsConfig so force a full goal state refresh
            self.update_goal_state(force_update=True)
            extensions_goal_state = self.get_extensions_goal_state()

        if extensions_goal_state.get_status_upload_blob() is None:
            raise ProtocolNotFoundError("Status upload uri is missing")

        blob_type = extensions_goal_state.get_status_upload_blob_type()

        try:
            self.status_blob.prepare(blob_type)
        except Exception as e:
            raise ProtocolError("Exception creating status blob: {0}".format(ustr(e)))

        # Swap the order of use for the HostPlugin vs. the "direct" route.
        # Prefer the use of HostPlugin. If HostPlugin fails fall back to the
        # direct route.
        #
        # The code previously preferred the "direct" route always, and only fell back
        # to the HostPlugin *if* there was an error. We would like to move to
        # the HostPlugin for all traffic, but this is a big change.  We would like
        # to see how this behaves at scale, and have a fallback should things go
        # wrong. This is why we try HostPlugin then direct.
        try:
            host = self.get_host_plugin()
            host.put_vm_status(self.status_blob, extensions_goal_state.get_status_upload_blob(), extensions_goal_state.get_status_upload_blob_type())
            return
        except ResourceGoneError:
            # refresh the host plugin client and try again on the next iteration of the main loop
            self.update_host_plugin_from_goal_state()
            return
        except Exception as e:
            # for all other errors, fall back to direct
            msg = "Falling back to direct upload: {0}".format(ustr(e))
            self.report_status_event(msg, is_success=True)

        try:
            if self.status_blob.upload(extensions_goal_state.get_status_upload_blob()):
                return
        except Exception as e:
            msg = "Exception uploading status blob: {0}".format(ustr(e))
            self.report_status_event(msg, is_success=False)

        raise ProtocolError("Failed to upload status blob via either channel")

    def report_role_prop(self, thumbprint):
        goal_state = self.get_goal_state()
        role_prop = _build_role_properties(goal_state.container_id,
                                           goal_state.role_instance_id,
                                           thumbprint)
        role_prop = role_prop.encode("utf-8")
        role_prop_uri = ROLE_PROP_URI.format(self.get_endpoint())
        headers = self.get_header_for_xml_content()
        try:
            resp = self.call_wireserver(restutil.http_post,
                                        role_prop_uri,
                                        role_prop,
                                        headers=headers)
        except HttpError as e:
            raise ProtocolError((u"Failed to send role properties: "
                                 u"{0}").format(e))
        if resp.status != httpclient.ACCEPTED:
            raise ProtocolError((u"Failed to send role properties: "
                                 u",{0}: {1}").format(resp.status,
                                                      resp.read()))

    def report_health(self, status, substatus, description):
        goal_state = self.get_goal_state()
        health_report = _build_health_report(goal_state.incarnation,
                                             goal_state.container_id,
                                             goal_state.role_instance_id,
                                             status,
                                             substatus,
                                             description)
        health_report = health_report.encode("utf-8")
        health_report_uri = HEALTH_REPORT_URI.format(self.get_endpoint())
        headers = self.get_header_for_xml_content()
        try:
            # 30 retries with 10s sleep gives ~5min for wireserver updates;
            # this is retried 3 times with 15s sleep before throwing a
            # ProtocolError, for a total of ~15min.
            resp = self.call_wireserver(restutil.http_post,
                                        health_report_uri,
                                        health_report,
                                        headers=headers,
                                        max_retry=30,
                                        retry_delay=15)
        except HttpError as e:
            raise ProtocolError((u"Failed to send provision status: "
                                 u"{0}").format(e))
        if restutil.request_failed(resp):
            raise ProtocolError((u"Failed to send provision status: "
                                 u",{0}: {1}").format(resp.status,
                                                      resp.read()))

    def send_encoded_event(self, provider_id, event_str, encoding='utf8'):
        uri = TELEMETRY_URI.format(self.get_endpoint())
        data_format_header = ustr('<?xml version="1.0"?><TelemetryData version="1.0"><Provider id="{0}">').format(
            provider_id).encode(encoding)
        data_format_footer = ustr('</Provider></TelemetryData>').encode(encoding)
        # Event string should already be encoded by the time it gets here, to avoid double encoding,
        # dividing it into parts.
        data = data_format_header + event_str + data_format_footer
        try:
            header = self.get_header_for_xml_content()
            # NOTE: The call to wireserver requests utf-8 encoding in the headers, but the body should not
            #       be encoded: some nodes in the telemetry pipeline do not support utf-8 encoding.
            resp = self.call_wireserver(restutil.http_post, uri, data, header)
        except HttpError as e:
            raise ProtocolError("Failed to send events:{0}".format(e))

        if restutil.request_failed(resp):
            logger.verbose(resp.read())
            raise ProtocolError(
                "Failed to send events:{0}".format(resp.status))

    def report_event(self, events_iterator):
        buf = {}
        debug_info = CollectOrReportEventDebugInfo(operation=CollectOrReportEventDebugInfo.OP_REPORT)
        events_per_provider = defaultdict(int)

        def _send_event(provider_id, debug_info):
            try:
                self.send_encoded_event(provider_id, buf[provider_id])
            except UnicodeError as uni_error:
                debug_info.update_unicode_error(uni_error)
            except Exception as error:
                debug_info.update_op_error(error)

        # Group events by providerId
        for event in events_iterator:
            try:
                if event.providerId not in buf:
                    buf[event.providerId] = b""
                event_str = event_to_v1_encoded(event)

                if len(event_str) >= MAX_EVENT_BUFFER_SIZE:
                    # Ignore single events that are too large to send out
                    details_of_event = [ustr(x.name) + ":" + ustr(x.value) for x in event.parameters if x.name in
                                        [GuestAgentExtensionEventsSchema.Name, GuestAgentExtensionEventsSchema.Version,
                                         GuestAgentExtensionEventsSchema.Operation,
                                         GuestAgentExtensionEventsSchema.OperationSuccess]]
                    logger.periodic_warn(logger.EVERY_HALF_HOUR,
                                         "Single event too large: {0}, with the length: {1} more than the limit({2})"
                                         .format(str(details_of_event), len(event_str), MAX_EVENT_BUFFER_SIZE))
                    continue

                # If buffer is full, send out the events in buffer and reset buffer
                if len(buf[event.providerId] + event_str) >= MAX_EVENT_BUFFER_SIZE:
                    logger.verbose("No of events this request = {0}".format(events_per_provider[event.providerId]))
                    _send_event(event.providerId, debug_info)
                    buf[event.providerId] = b""
                    events_per_provider[event.providerId] = 0

                # Add encoded events to the buffer
                buf[event.providerId] = buf[event.providerId] + event_str
                events_per_provider[event.providerId] += 1

            except Exception as error:
                logger.warn("Unexpected error when generating Events:{0}", textutil.format_exception(error))

        # Send out all events left in buffer.
        for provider_id in list(buf.keys()):
            if buf[provider_id]:
                logger.verbose("No of events this request = {0}".format(events_per_provider[provider_id]))
                _send_event(provider_id, debug_info)

        debug_info.report_debug_info()

    def report_status_event(self, message, is_success):
        report_event(op=WALAEventOperation.ReportStatus,
                     is_success=is_success,
                     message=message,
                     log_event=not is_success)

    def get_header(self):
        return {
            "x-ms-agent-name": "WALinuxAgent",
            "x-ms-version": PROTOCOL_VERSION
        }

    def get_header_for_xml_content(self):
        return {
            "x-ms-agent-name": "WALinuxAgent",
            "x-ms-version": PROTOCOL_VERSION,
            "Content-Type": "text/xml;charset=utf-8"
        }

    def get_header_for_cert(self):
        trans_cert_file = os.path.join(conf.get_lib_dir(),
                                       TRANSPORT_CERT_FILE_NAME)
        content = self.fetch_cache(trans_cert_file)
        cert = get_bytes_from_pem(content)
        return {
            "x-ms-agent-name": "WALinuxAgent",
            "x-ms-version": PROTOCOL_VERSION,
            "x-ms-cipher-name": "DES_EDE3_CBC",
            "x-ms-guest-agent-public-x509-cert": cert
        }

    def get_host_plugin(self):
        if self._host_plugin is None:
            goal_state = GoalState(self)
            self._set_host_plugin(HostPluginProtocol(self.get_endpoint(),
                                                     goal_state.container_id,
                                                     goal_state.role_config_name))
        return self._host_plugin

    def has_artifacts_profile_blob(self):
        extensions_goal_state = self.get_extensions_goal_state()
        return extensions_goal_state and not \
            textutil.is_str_none_or_whitespace(extensions_goal_state.artifacts_profile_blob)

    def get_artifacts_profile_through_host(self, blob):
        host = self.get_host_plugin()
        uri, headers = host.get_artifact_request(blob)
        profile, _ = self.fetch(uri, headers, use_proxy=False)
        return profile

    def get_artifacts_profile(self):
        artifacts_profile = None

        if self.has_artifacts_profile_blob():
            blob = self.get_extensions_goal_state().artifacts_profile_blob
            direct_func = lambda: self.fetch(blob)[0]
            # NOTE: the host_func may be called after refreshing the goal state, be careful about any goal state data
            # in the lambda.
            host_func = lambda: self.get_artifacts_profile_through_host(blob)

            logger.verbose("Retrieving the artifacts profile")

            try:
                profile = self.send_request_using_appropriate_channel(direct_func, host_func)
                if profile is None:
                    logger.warn("Failed to fetch artifacts profile from blob {0}", blob)
                    return None
            except Exception as error:
                logger.warn("Exception retrieving artifacts profile from blob {0}. Error: {1}".format(blob, ustr(error)))
                return None

            if not textutil.is_str_empty(profile):
                logger.verbose("Artifacts profile downloaded")
                try:
                    artifacts_profile = InVMArtifactsProfile(profile)
                except Exception:
                    logger.warn("Could not parse artifacts profile blob")
                    msg = "Content: [{0}]".format(profile)
                    logger.verbose(msg)

                    report_event(op=WALAEventOperation.ArtifactsProfileBlob,
                                 is_success=False,
                                 message=msg,
                                 log_event=False)

        return artifacts_profile

    def upload_logs(self, content):
        host_func = lambda: self._upload_logs_through_host(content)
        return self._call_hostplugin_with_container_check(host_func)

    def _upload_logs_through_host(self, content):
        host = self.get_host_plugin()
        return host.put_vm_log(content)


class VersionInfo(object):
    def __init__(self, xml_text):
        """
        Query endpoint server for wire protocol version.
        Fail if our desired protocol version is not seen.
        """
        logger.verbose("Load Version.xml")
        self.parse(xml_text)

    def parse(self, xml_text):
        xml_doc = parse_doc(xml_text)
        preferred = find(xml_doc, "Preferred")
        self.preferred = findtext(preferred, "Version")
        logger.info("Fabric preferred wire protocol version:{0}",
                    self.preferred)

        self.supported = []
        supported = find(xml_doc, "Supported")
        supported_version = findall(supported, "Version")
        for node in supported_version:
            version = gettext(node)
            logger.verbose("Fabric supported wire protocol version:{0}",
                           version)
            self.supported.append(version)

    def get_preferred(self):
        return self.preferred

    def get_supported(self):
        return self.supported


class ExtensionManifest(object): 
    def __init__(self, xml_text):
        if xml_text is None:
            raise ValueError("ExtensionManifest is None")
        logger.verbose("Load ExtensionManifest.xml")
        self.pkg_list = ExtHandlerPackageList()
        self._parse(xml_text)

    def _parse(self, xml_text):
        xml_doc = parse_doc(xml_text)
        self._handle_packages(findall(find(xml_doc,
                                           "Plugins"),
                                      "Plugin"),
                              False)
        self._handle_packages(findall(find(xml_doc,
                                           "InternalPlugins"),
                                      "Plugin"),
                              True)

    def _handle_packages(self, packages, isinternal):
        for package in packages:
            version = findtext(package, "Version")

            disallow_major_upgrade = findtext(package,
                                              "DisallowMajorVersionUpgrade")
            if disallow_major_upgrade is None:
                disallow_major_upgrade = ''
            disallow_major_upgrade = disallow_major_upgrade.lower() == "true"

            uris = find(package, "Uris")
            uri_list = findall(uris, "Uri")
            uri_list = [gettext(x) for x in uri_list]
            pkg = ExtHandlerPackage()
            pkg.version = version
            pkg.disallow_major_upgrade = disallow_major_upgrade
            for uri in uri_list:
                pkg_uri = ExtHandlerVersionUri()
                pkg_uri.uri = uri
                pkg.uris.append(pkg_uri)

            pkg.isinternal = isinternal
            self.pkg_list.versions.append(pkg)


# Do not extend this class
class InVMArtifactsProfile(object):
    """
    deserialized json string of InVMArtifactsProfile.
    It is expected to contain the following fields:
    * inVMArtifactsProfileBlobSeqNo
    * profileId (optional)
    * onHold (optional)
    * certificateThumbprint (optional)
    * encryptedHealthChecks (optional)
    * encryptedApplicationProfile (optional)
    """

    def __init__(self, artifacts_profile):
        if not textutil.is_str_empty(artifacts_profile):
            self.__dict__.update(parse_json(artifacts_profile))

    def is_on_hold(self):
        # hasattr() is not available in Python 2.6
        if 'onHold' in self.__dict__:
            return str(self.onHold).lower() == 'true'  # pylint: disable=E1101
        return False


class _ErrorReporter(object):
    _MaxErrors = 5  # Max number of error reported by period
    _Period = timedelta(hours=1)  # How often to report _errors

    def __init__(self, operation):
        self._operation = operation
        self._error_count = 0
        self._next_period = datetime.now() + _ErrorReporter._Period
        self._log_message_prefix = "[{0}] [Informational only, the Agent will continue normal operation]".format(self._operation)

    def report_error(self, error):
        self._error_count += 1
        if self._error_count <= _ErrorReporter._MaxErrors:
            logger.info("{0} {1}", self._log_message_prefix, error)
            add_event(op=self._operation, message=error, is_success=False, log_event=False)

    def report_summary(self):
        if datetime.now() >= self._next_period:
            self._next_period = datetime.now() + _ErrorReporter._Period
            if self._error_count > 0:
                message = "{0} errors in the last period".format(self._error_count)
                logger.info("{0} {1}", self._log_message_prefix, message)
                add_event(op=self._operation, message=message, is_success=False, log_event=False)
                self._error_count = 0
