# Integrate with the kubernetes events API. 
# This module sends events to Kubernetes, and also captures/tracks all events
# in the rook-ceph namespace so kubernetes activity like pod restarts,
# imagepulls etc can be seen from within the ceph cluster itself.
#
# To interact with the events API, the mgr service to access needs to be 
# granted additional permissions
# e.g. kubectl -n rook-ceph edit clusterrole rook-ceph-mgr-cluster-rules
#
# These are the changes needed;
# - apiGroups:
#   - ""
#   resources:
#   - events
#   verbs:
#   - create
#   - patch
#   - list
#   - get
#   - watch


import os
import re
import sys
import time
import json
import yaml
import errno
import socket
import base64
import logging
import tempfile
import threading

from urllib.parse import urlparse
from datetime import tzinfo, datetime, timedelta
   
from urllib3.exceptions import MaxRetryError,ProtocolError
from collections import OrderedDict

import rados
from mgr_module import MgrModule, NotifyType
from mgr_util import verify_cacrt, ServerConfigException

try:
    import queue
except ImportError:
    # python 2.7.5
    import Queue as queue
finally:
    # python 2.7.15 or python3
    event_queue = queue.Queue()

try:
    from kubernetes import client, config, watch
    from kubernetes.client.rest import ApiException
except ImportError:
    kubernetes_imported = False
    client = None
    config = None
    watch = None
else:
    kubernetes_imported = True

    # The watch.Watch.stream method can provide event objects that have involved_object = None
    # which causes an exception in the generator. A workaround is discussed for a similar issue
    # in https://github.com/kubernetes-client/python/issues/376 which has been used here
    # pylint: disable=no-member
    from kubernetes.client.models.v1_event import V1Event
    def local_involved_object(self, involved_object):
        if involved_object is None:
            involved_object = client.V1ObjectReference(api_version="1")
        self._involved_object = involved_object
    V1Event.involved_object = V1Event.involved_object.setter(local_involved_object)

log = logging.getLogger(__name__)

# use a simple local class to represent UTC
# datetime pkg modules vary between python2 and 3 and pytz is not available on older
# ceph container images, so taking a pragmatic approach!
class UTC(tzinfo):
    def utcoffset(self, dt):
        return timedelta(0)

    def tzname(self, dt):
        return "UTC"

    def dst(self, dt):
        return timedelta(0)


def text_suffix(num):
    """Define a text suffix based on a value i.e. turn host into hosts"""
    return '' if num == 1 else 's'


def create_temp_file(fname, content, suffix=".tmp"):
    """Create a temp file 

    Attempt to create an temporary file containing the given content

    Returns:
    str .. full path to the temporary file

    Raises:
    OSError: problems creating the file

    """

    if content is not None:
        file_name = os.path.join(tempfile.gettempdir(), fname + suffix)

        try:
            with open(file_name, "w") as f:
                f.write(content)
        except OSError as e:
            raise OSError("Unable to create temporary file : {}".format(str(e)))

    return file_name


class HealthCheck(object):
    """Transform a healthcheck msg into it's component parts"""

    def __init__(self, msg, msg_level):

        # msg looks like
        #
        # Health check failed: Reduced data availability: 100 pgs inactive (PG_AVAILABILITY)
        # Health check cleared: OSDMAP_FLAGS (was: nodown flag(s) set)
        # Health check failed: nodown flag(s) set (OSDMAP_FLAGS)
        #
        self.msg = None
        self.name = None
        self.text = None
        self.valid = False
        
        if msg.lower().startswith('health check'):

            self.valid = True
            self.msg = msg
            msg_tokens = self.msg.split()
            
            if msg_level == 'INF':
                self.text = ' '.join(msg_tokens[3:])
                self.name = msg_tokens[3]   # health check name e.g. OSDMAP_FLAGS
            else:   # WRN or ERR
                self.text = ' '.join(msg_tokens[3:-1])
                self.name = msg_tokens[-1][1:-1]


class LogEntry(object):
    """Generic 'log' object"""

    reason_map = {
        "audit": "Audit",
        "cluster": "HealthCheck",
        "config": "ClusterChange",
        "heartbeat":"Heartbeat",
        "startup": "Started"
    }

    def __init__(self, source, msg, msg_type, level, tstamp=None):

        self.source = source
        self.msg = msg
        self.msg_type = msg_type
        self.level = level
        self.tstamp = tstamp
        self.healthcheck = None
        
        if 'health check ' in self.msg.lower():
            self.healthcheck = HealthCheck(self.msg, self.level)

    
    def __str__(self):
        return "source={}, msg_type={}, msg={}, level={}, tstamp={}".format(self.source,
                                                                            self.msg_type,
                                                                            self.msg,
                                                                            self.level,
                                                                            self.tstamp)

    @property
    def cmd(self):
        """Look at the msg string and extract the command content"""

        # msg looks like 'from=\'client.205306 \' entity=\'client.admin\' cmd=\'[{"prefix": "osd set", "key": "nodown"}]\': finished'
        if self.msg_type != 'audit':
            return None
        else:
            _m=self.msg[:-10].replace("\'","").split("cmd=")
            _s='"cmd":{}'.format(_m[1])
            cmds_list = json.loads('{' + _s + '}')['cmd']

            # TODO. Assuming only one command was issued for now
            _c = cmds_list[0]
            return "{} {}".format(_c['prefix'], _c.get('key', ''))
    
    @property
    def event_type(self):
        return 'Normal' if self.level == 'INF' else 'Warning'
    
    @property
    def event_reason(self):
        return self.reason_map[self.msg_type]

    @property
    def event_name(self):
        if self.msg_type == 'heartbeat':
            return 'mgr.Heartbeat'
        elif self.healthcheck:
            return 'mgr.health.{}'.format(self.healthcheck.name)
        elif self.msg_type == 'audit':
            return 'mgr.audit.{}'.format(self.cmd).replace(' ', '_')
        elif self.msg_type == 'config':
            return 'mgr.ConfigurationChange'
        elif self.msg_type == 'startup':
            return "mgr.k8sevents-module"
        else:
            return None
   
    @property
    def event_entity(self):
        if self.msg_type == 'audit':
            return self.msg.replace("\'","").split('entity=')[1].split(' ')[0]
        else:
            return None
    
    @property
    def event_msg(self):
        if self.msg_type == 'audit':
            return "Client '{}' issued: ceph {}".format(self.event_entity, self.cmd)

        elif self.healthcheck:
            return self.healthcheck.text
        else:
            return self.msg


class BaseThread(threading.Thread):
    health = 'OK'
    reported = False
    daemon = True


def clean_event(event):
    """ clean an event record """
    if not event.first_timestamp:
        log.error("first_timestamp is empty")
        if event.metadata.creation_timestamp:
            log.error("setting first_timestamp to the creation timestamp")
            event.first_timestamp = event.metadata.creation_timestamp
        else:
            log.error("defaulting event first timestamp to current datetime")
            event.first_timestamp = datetime.datetime.now()

    if not event.last_timestamp:
        log.error("setting event last timestamp to {}".format(event.first_timestamp))
        event.last_timestamp = event.first_timestamp

    if not event.count:
        event.count = 1

    return event


class NamespaceWatcher(BaseThread):
    """Watch events in a given namespace 
    
    Using the watch package we can listen to event traffic in the namespace to 
    get an idea of what kubernetes related events surround the ceph cluster. The
    thing to bear in mind is that events have a TTL enforced by the kube-apiserver
    so this stream will only really show activity inside this retention window.
    """

    def __init__(self, api_client_config, namespace=None):
        super(NamespaceWatcher, self).__init__()

        if api_client_config:
            self.api = client.CoreV1Api(api_client_config)
        else:
            self.api = client.CoreV1Api()

        self.namespace = namespace

        self.events = OrderedDict()
        self.lock = threading.Lock()
        self.active = None
        self.resource_version = None

    def fetch(self):
        # clear the cache on every call to fetch
        self.events.clear()
        try:
            resp = self.api.list_namespaced_event(self.namespace)
        # TODO - Perhaps test for auth problem to be more specific in the except clause?
        except:
            self.active = False
            self.health = "Unable to access events API (list_namespaced_event call failed)"
            log.warning(self.health)
        else:
            self.active = True
            self.resource_version = resp.metadata.resource_version
            
            for item in resp.items:
                self.events[item.metadata.name] = clean_event(item)
            log.info('Added {} events'.format(len(resp.items)))

    def run(self):
        self.fetch()
        func = getattr(self.api, "list_namespaced_event")

        if self.active:
            log.info("Namespace event watcher started")

            
            while True:

                try:
                    w = watch.Watch()
                    # execute generator to continually watch resource for changes
                    for item in w.stream(func, namespace=self.namespace, resource_version=self.resource_version, watch=True):
                        obj = item['object']

                        with self.lock:

                            if item['type'] in ['ADDED', 'MODIFIED']:
                                self.events[obj.metadata.name] = clean_event(obj)

                            elif item['type'] == 'DELETED':
                                del self.events[obj.metadata.name]
                            
                # TODO test the exception for auth problem (403?)
    
                # Attribute error is generated when urllib3 on the system is old and doesn't have a
                # read_chunked method
                except AttributeError as e:
                    self.health = ("Error: Unable to 'watch' events API in namespace '{}' - "
                                "urllib3 too old? ({})".format(self.namespace, e))
                    self.active = False
                    log.warning(self.health)
                    break

                except ApiException as e:
                    # refresh the resource_version & watcher
                    log.warning("API exception caught in watcher ({})".format(e))
                    log.warning("Restarting namespace watcher")
                    self.fetch()

                except ProtocolError as e:
                    log.warning("Namespace watcher hit protocolerror ({}) - restarting".format(e))
                    self.fetch()

                except Exception:
                    self.health = "{} Exception at {}".format(
                        sys.exc_info()[0].__name__,
                        datetime.strftime(datetime.now(),"%Y/%m/%d %H:%M:%S")
                    )
                    log.exception(self.health)
                    self.active = False
                    break

            log.warning("Namespace event watcher stopped")


class KubernetesEvent(object):

    def __init__(self, log_entry, unique_name=True, api_client_config=None, namespace=None):

        if api_client_config:
            self.api = client.CoreV1Api(api_client_config)
        else:
            self.api = client.CoreV1Api()

        self.namespace = namespace

        self.event_name = log_entry.event_name
        self.message = log_entry.event_msg
        self.event_type = log_entry.event_type
        self.event_reason = log_entry.event_reason
        self.unique_name = unique_name

        self.host = os.environ.get('NODE_NAME', os.environ.get('HOSTNAME', 'UNKNOWN'))

        self.api_status = 200
        self.count = 1
        self.first_timestamp = None
        self.last_timestamp = None

    @property
    def type(self):
        """provide a type property matching a V1Event object"""
        return self.event_type

    @property
    def event_body(self):
        if self.unique_name:
            obj_meta = client.V1ObjectMeta(name="{}".format(self.event_name)) 
        else:
            obj_meta = client.V1ObjectMeta(generate_name="{}".format(self.event_name))

        # field_path is needed to prevent problems in the namespacewatcher when
        # deleted event are received
        obj_ref = client.V1ObjectReference(kind="CephCluster",
                                           field_path='spec.containers{mgr}', 
                                           name=self.event_name, 
                                           namespace=self.namespace)

        event_source = client.V1EventSource(component="ceph-mgr", 
                                            host=self.host)
        return  client.V1Event(
                    involved_object=obj_ref, 
                    metadata=obj_meta, 
                    message=self.message, 
                    count=self.count, 
                    type=self.event_type,
                    reason=self.event_reason,
                    source=event_source, 
                    first_timestamp=self.first_timestamp,
                    last_timestamp=self.last_timestamp
                )

    def write(self):

        now=datetime.now(UTC())

        self.first_timestamp = now
        self.last_timestamp = now

        try:
            self.api.create_namespaced_event(self.namespace, self.event_body)
        except (OSError, ProtocolError):
            # unable to reach to the API server
            log.error("Unable to reach API server")
            self.api_status = 400
        except MaxRetryError:
            # k8s config has not be defined properly
            log.error("multiple attempts to connect to the API have failed") 
            self.api_status = 403       # Forbidden
        except ApiException as e:
            log.debug("event.write status:{}".format(e.status))
            self.api_status = e.status
            if e.status == 409:
                log.debug("attempting event update for an existing event")
                # 409 means the event is there already, so read it back (v1Event object returned)
                # this could happen if the event has been created, and then the k8sevent module
                # disabled and reenabled - i.e. the internal event tracking no longer matches k8s
                response = self.api.read_namespaced_event(self.event_name, self.namespace)
                #
                # response looks like
                #
                # {'action': None,
                # 'api_version': 'v1',
                # 'count': 1,
                # 'event_time': None,
                # 'first_timestamp': datetime.datetime(2019, 7, 18, 5, 24, 59, tzinfo=tzlocal()),
                # 'involved_object': {'api_version': None,
                #                     'field_path': None,
                #                     'kind': 'CephCluster',
                #                     'name': 'ceph-mgr.k8sevent-module',
                #                     'namespace': 'rook-ceph',
                #                     'resource_version': None,
                #                     'uid': None},
                # 'kind': 'Event',
                # 'last_timestamp': datetime.datetime(2019, 7, 18, 5, 24, 59, tzinfo=tzlocal()),
                # 'message': 'Ceph log -> event tracking started',
                # 'metadata': {'annotations': None,
                #             'cluster_name': None,
                #             'creation_timestamp': datetime.datetime(2019, 7, 18, 5, 24, 59, tzinfo=tzlocal()),
                #             'deletion_grace_period_seconds': None,
                #             'deletion_timestamp': None,
                #             'finalizers': None,
                #             'generate_name': 'ceph-mgr.k8sevent-module',
                #             'generation': None,
                #             'initializers': None,
                #             'labels': None,
                #             'name': 'ceph-mgr.k8sevent-module5z7kq',
                #             'namespace': 'rook-ceph',
                #             'owner_references': None,
                #             'resource_version': '1195832',
                #             'self_link': '/api/v1/namespaces/rook-ceph/events/ceph-mgr.k8sevent-module5z7kq',
                #             'uid': '62fde5f1-a91c-11e9-9c80-6cde63a9debf'},
                # 'reason': 'Started',
                # 'related': None,
                # 'reporting_component': '',
                # 'reporting_instance': '',
                # 'series': None,
                # 'source': {'component': 'ceph-mgr', 'host': 'minikube'},
                # 'type': 'Normal'}

                # conflict event already exists
                # read it
                # update : count and last_timestamp and msg

                self.count = response.count + 1
                self.first_timestamp = response.first_timestamp
                try:
                    self.api.patch_namespaced_event(self.event_name, self.namespace, self.event_body)
                except ApiException as e:
                    log.error("event.patch failed for {} with status code:{}".format(self.event_name, e.status))
                    self.api_status = e.status
                else:
                    log.debug("event {} patched".format(self.event_name))
                    self.api_status = 200

        else:
            log.debug("event {} created successfully".format(self.event_name))
            self.api_status = 200

    @property
    def api_success(self):
        return self.api_status == 200

    def update(self, log_entry):
        self.message = log_entry.event_msg
        self.event_type = log_entry.event_type
        self.last_timestamp = datetime.now(UTC())
        self.count += 1
        log.debug("performing event update for {}".format(self.event_name))

        try:
            self.api.patch_namespaced_event(self.event_name, self.namespace, self.event_body)
        except ApiException as e:
            log.error("event patch call failed: {}".format(e.status))
            if e.status == 404:
                # tried to patch, but hit a 404. The event's TTL must have been reached, and 
                # pruned by the kube-apiserver
                log.debug("event not found, so attempting to create it")
                try:
                    self.api.create_namespaced_event(self.namespace, self.event_body)
                except ApiException as e:
                    log.error("unable to create the event: {}".format(e.status))
                    self.api_status = e.status
                else:
                    log.debug("event {} created successfully".format(self.event_name))
                    self.api_status = 200
        else:
            log.debug("event {} updated".format(self.event_name))
            self.api_status = 200 


class EventProcessor(BaseThread):
    """Handle a global queue used to track events we want to send/update to kubernetes"""

    can_run = True

    def __init__(self, config_watcher, event_retention_days, api_client_config, namespace):
        super(EventProcessor, self).__init__()

        self.events = dict()
        self.config_watcher = config_watcher
        self.event_retention_days = event_retention_days
        self.api_client_config = api_client_config
        self.namespace = namespace

    def startup(self):
        """Log an event to show we're active"""
        
        event = KubernetesEvent(
            LogEntry(
                source='self',
                msg='Ceph log -> event tracking started',
                msg_type='startup',
                level='INF',
                tstamp=None
            ),
            unique_name=False,
            api_client_config=self.api_client_config,
            namespace=self.namespace
        )
        
        event.write()
        return event.api_success
    
    @property
    def ok(self):
        return self.startup()

    def prune_events(self):
        log.debug("prune_events - looking for old events to remove from cache")
        oldest = datetime.now(UTC()) - timedelta(days=self.event_retention_days)
        local_events = dict(self.events)

        for event_name in sorted(local_events,
                                 key = lambda name: local_events[name].last_timestamp):
            event = local_events[event_name]
            if event.last_timestamp >= oldest:
                break
            else:
                # drop this event
                log.debug("prune_events - removing old event : {}".format(event_name))
                del self.events[event_name]

    def process(self, log_object):
        
        log.debug("log entry being processed : {}".format(str(log_object)))

        event_out = False
        unique_name = True

        if log_object.msg_type == 'audit':
            # audit traffic : operator commands
            if log_object.msg.endswith('finished'):
                log.debug("K8sevents received command finished msg")
                event_out = True
            else:
                # NO OP - ignoring 'dispatch' log records
                return
        
        elif log_object.msg_type == 'cluster':
            # cluster messages : health checks
            if log_object.event_name:
                event_out = True

        elif log_object.msg_type == 'config':
            # configuration checker messages 
            event_out = True
            unique_name = False
            
        elif log_object.msg_type == 'heartbeat':
            # hourly health message summary from Ceph
            event_out = True
            unique_name = False
            log_object.msg = str(self.config_watcher)

        else:
            log.warning("K8sevents received unknown msg_type - {}".format(log_object.msg_type))

        if event_out:
            log.debug("k8sevents sending event to kubernetes")
            # we don't cache non-unique events like heartbeats or config changes
            if not unique_name or log_object.event_name not in self.events.keys():
                event = KubernetesEvent(log_entry=log_object,
                                        unique_name=unique_name,
                                        api_client_config=self.api_client_config,
                                        namespace=self.namespace)
                event.write()
                log.debug("event(unique={}) creation ended : {}".format(unique_name, event.api_status))
                if event.api_success and unique_name:
                    self.events[log_object.event_name] = event
            else:
                event = self.events[log_object.event_name]
                event.update(log_object)
                log.debug("event update ended : {}".format(event.api_status))

            self.prune_events()

        else:
            log.debug("K8sevents ignored message : {}".format(log_object.msg))

    def run(self):
        log.info("Ceph event processing thread started, "
                 "event retention set to {} days".format(self.event_retention_days))

        while True:

            try:
                log_object = event_queue.get(block=False)
            except queue.Empty:
                pass
            else:
                try:
                    self.process(log_object)
                except Exception:
                    self.health = "{} Exception at {}".format(
                        sys.exc_info()[0].__name__,
                        datetime.strftime(datetime.now(),"%Y/%m/%d %H:%M:%S")
                    )
                    log.exception(self.health)
                    break
            
            if not self.can_run:
                break

            time.sleep(0.5)

        log.warning("Ceph event processing thread stopped")


class ListDiff(object):
    def __init__(self, before, after):
        self.before = set(before)
        self.after = set(after)

    @property
    def removed(self):
        return list(self.before - self.after)

    @property
    def added(self):
        return list(self.after - self.before)

    @property
    def is_equal(self):
        return self.before == self.after


class CephConfigWatcher(BaseThread):
    """Detect configuration changes within the cluster and generate human readable events"""

    def __init__(self, mgr):
        super(CephConfigWatcher, self).__init__()
        self.mgr = mgr
        self.server_map = dict()
        self.osd_map = dict()
        self.pool_map = dict()
        self.service_map = dict()
        
        self.config_check_secs = mgr.config_check_secs
    
    @property
    def raw_capacity(self):
        # Note. if the osd's are not online the capacity field will be 0
        return sum([self.osd_map[osd]['capacity'] for osd in self.osd_map])
    
    @property
    def num_servers(self):
        return len(self.server_map.keys())

    @property
    def num_osds(self):
        return len(self.osd_map.keys())
    
    @property
    def num_pools(self):
        return len(self.pool_map.keys())

    def __str__(self):
        s = ''

        s += "{} : {:>3} host{}, {} pool{}, {} OSDs. Raw Capacity {}B".format(
            json.loads(self.mgr.get('health')['json'])['status'],
            self.num_servers, 
            text_suffix(self.num_servers),
            self.num_pools, 
            text_suffix(self.num_pools),
            self.num_osds, 
            MgrModule.to_pretty_iec(self.raw_capacity))
        return s

    def fetch_servers(self):
        """Return a server summary, and service summary"""
        servers = self.mgr.list_servers()
        server_map = dict()         # host -> services
        service_map = dict()        # service -> host
        for server_info in servers:
            services = dict()
            for svc in server_info['services']:
                if svc.get('type') in services.keys():
                    services[svc.get('type')].append(svc.get('id'))
                else:
                    services[svc.get('type')] = list([svc.get('id')])
                # maintain the service xref map service -> host and version
                service_map[(svc.get('type'), str(svc.get('id')))] = server_info.get('hostname', '')
            server_map[server_info.get('hostname')] = services

        return server_map, service_map
    
    def fetch_pools(self):
        interesting = ["type", "size", "min_size"]
        # pools = [{'pool': 1, 'pool_name': 'replicapool', 'flags': 1, 'flags_names': 'hashpspool', 
        #           'type': 1, 'size': 3, 'min_size': 1, 'crush_rule': 1, 'object_hash': 2, 'pg_autoscale_mode': 'warn', 
        #           'pg_num': 100, 'pg_placement_num': 100, 'pg_placement_num_target': 100, 'pg_num_target': 100, 'pg_num_pending': 100, 
        #           'last_pg_merge_meta': {'ready_epoch': 0, 'last_epoch_started': 0, 'last_epoch_clean': 0, 'source_pgid': '0.0', 
        #           'source_version': "0'0", 'target_version': "0'0"}, 'auid': 0, 'snap_mode': 'selfmanaged', 'snap_seq': 0, 'snap_epoch': 0,
        #           'pool_snaps': [], 'quota_max_bytes': 0, 'quota_max_objects': 0, 'tiers': [], 'tier_of': -1, 'read_tier': -1, 
        #           'write_tier': -1, 'cache_mode': 'none', 'target_max_bytes': 0, 'target_max_objects': 0, 
        #           'cache_target_dirty_ratio_micro': 400000, 'cache_target_dirty_high_ratio_micro': 600000, 
        #           'cache_target_full_ratio_micro': 800000, 'cache_min_flush_age': 0, 'cache_min_evict_age': 0, 
        #           'erasure_code_profile': '', 'hit_set_params': {'type': 'none'}, 'hit_set_period': 0, 'hit_set_count': 0, 
        #           'use_gmt_hitset': True, 'min_read_recency_for_promote': 0, 'min_write_recency_for_promote': 0, 
        #           'hit_set_grade_decay_rate': 0, 'hit_set_search_last_n': 0, 'grade_table': [], 'stripe_width': 0, 
        #           'expected_num_objects': 0, 'fast_read': False, 'options': {}, 'application_metadata': {'rbd': {}}, 
        #           'create_time': '2019-08-02 02:23:01.618519', 'last_change': '19', 'last_force_op_resend': '0', 
        #           'last_force_op_resend_prenautilus': '0', 'last_force_op_resend_preluminous': '0', 'removed_snaps': '[]'}]
        pools = self.mgr.get('osd_map')['pools']
        pool_map = dict()
        for pool in pools:
            pool_map[pool.get('pool_name')] = {k:pool.get(k) for k in interesting}
        return pool_map


    def fetch_osd_map(self, service_map):
        """Create an osd map"""
        stats = self.mgr.get('osd_stats')

        osd_map = dict()

        devices = self.mgr.get('osd_map_crush')['devices']
        for dev in devices:
            osd_id = str(dev['id']) 
            osd_map[osd_id] = dict(
                deviceclass=dev.get('class'),
                capacity=0,
                hostname=service_map['osd', osd_id]
                )
        
        for osd_stat in stats['osd_stats']:
            osd_id = str(osd_stat.get('osd'))
            osd_map[osd_id]['capacity'] = osd_stat['statfs']['total']

        return osd_map

    def push_events(self, changes):
        """Add config change to the global queue to generate an event in kubernetes"""
        log.debug("{} events will be generated")
        for change in changes:
            event_queue.put(change)

    def _generate_config_logentry(self, msg):
        return LogEntry(
                source="config",
                msg_type="config",
                msg=msg,
                level='INF',
                tstamp=None
        )
    
    def _check_hosts(self, server_map):
        log.debug("K8sevents checking host membership")
        changes = list()
        servers = ListDiff(self.server_map.keys(), server_map.keys())
        if servers.is_equal:
            # no hosts have been added or removed
            pass
        else:
            # host changes detected, find out what
            host_msg = "Host '{}' has been {} the cluster"
            for new_server in servers.added:
                changes.append(self._generate_config_logentry(
                                    msg=host_msg.format(new_server, 'added to'))
                )

            for removed_server in servers.removed:
                changes.append(self._generate_config_logentry(
                                    msg=host_msg.format(removed_server, 'removed from'))
                )

        return changes

    def _check_osds(self,server_map, osd_map):
        log.debug("K8sevents checking OSD configuration")
        changes = list()
        before_osds = list()
        for svr in self.server_map:
            before_osds.extend(self.server_map[svr].get('osd',[]))

        after_osds = list()
        for svr in server_map:
            after_osds.extend(server_map[svr].get('osd',[]))
        
        if set(before_osds) == set(after_osds):
            # no change in osd id's
            pass
        else:
            # osd changes detected
            osd_msg = "Ceph OSD '{}' ({} @ {}B) has been {} host {}"

            osds = ListDiff(before_osds, after_osds)
            for new_osd in osds.added:
                changes.append(self._generate_config_logentry(
                                    msg=osd_msg.format(
                                            new_osd, 
                                            osd_map[new_osd]['deviceclass'],
                                            MgrModule.to_pretty_iec(osd_map[new_osd]['capacity']),
                                            'added to',
                                            osd_map[new_osd]['hostname']))
                )

            for removed_osd in osds.removed:
                changes.append(self._generate_config_logentry(
                                    msg=osd_msg.format(
                                        removed_osd,
                                        osd_map[removed_osd]['deviceclass'],
                                        MgrModule.to_pretty_iec(osd_map[removed_osd]['capacity']),
                                        'removed from',
                                        osd_map[removed_osd]['hostname']))
                )

        return changes

    def _check_pools(self, pool_map):
        changes = list()
        log.debug("K8sevents checking pool configurations")
        if self.pool_map.keys() == pool_map.keys():
            # no pools added/removed
            pass
        else:
            # Pool changes
            pools = ListDiff(self.pool_map.keys(), pool_map.keys())
            pool_msg = "Pool '{}' has been {} the cluster"
            for new_pool in pools.added:
                changes.append(self._generate_config_logentry(
                                    msg=pool_msg.format(new_pool, 'added to'))
                )

            for removed_pool in pools.removed:
                changes.append(self._generate_config_logentry(
                                    msg=pool_msg.format(removed_pool, 'removed from'))
                )

        # check pool configuration changes
        for pool_name in pool_map:
            if not self.pool_map.get(pool_name, dict()):
                # pool didn't exist before so just skip the checks
                continue

            if pool_map[pool_name] == self.pool_map[pool_name]:
                # no changes - dicts match in key and value
                continue
            else:
                # determine the change and add it to the change list
                size_diff = pool_map[pool_name]['size'] - self.pool_map[pool_name]['size']
                if size_diff != 0:
                    if size_diff < 0:
                        msg = "Data protection level of pool '{}' reduced to {} copies".format(pool_name,
                                                                                               pool_map[pool_name]['size'])
                        level = 'WRN'
                    else:
                        msg = "Data protection level of pool '{}' increased to {} copies".format(pool_name,
                                                                                                 pool_map[pool_name]['size'])
                        level = 'INF'

                    changes.append(LogEntry(source="config",
                                msg_type="config",
                                msg=msg,
                                level=level,
                                tstamp=None)
                                )

                if pool_map[pool_name]['min_size'] != self.pool_map[pool_name]['min_size']:
                    changes.append(LogEntry(source="config",
                                msg_type="config",
                                msg="Minimum acceptable number of replicas in pool '{}' has changed".format(pool_name),
                                level='WRN',
                                tstamp=None)
                                )

        return changes

    def get_changes(self, server_map, osd_map, pool_map):
        """Detect changes in maps between current observation and the last"""

        changes = list()

        changes.extend(self._check_hosts(server_map))
        changes.extend(self._check_osds(server_map, osd_map))
        changes.extend(self._check_pools(pool_map))

        # FUTURE
        # Could generate an event if a ceph daemon has moved hosts
        # (assumes the ceph metadata host information is valid though!)

        return changes

    def run(self):
        log.info("Ceph configuration watcher started, interval set to {}s".format(self.config_check_secs))

        self.server_map, self.service_map = self.fetch_servers()
        self.pool_map = self.fetch_pools()

        self.osd_map = self.fetch_osd_map(self.service_map)
        
        while True:

            try:
                start_time = time.time()
                server_map, service_map = self.fetch_servers()
                pool_map = self.fetch_pools()
                osd_map = self.fetch_osd_map(service_map)

                changes = self.get_changes(server_map, osd_map, pool_map)
                if changes:
                    self.push_events(changes)

                self.osd_map = osd_map
                self.pool_map = pool_map
                self.server_map = server_map
                self.service_map = service_map

                checks_duration = int(time.time() - start_time)
                
                # check that the time it took to run the checks fits within the 
                # interval, and if not extend the interval and emit a log message
                # to show that the runtime for the checks exceeded the desired 
                # interval
                if checks_duration > self.config_check_secs:
                    new_interval = self.config_check_secs * 2
                    log.warning("K8sevents check interval warning. "
                                "Current checks took {}s, interval was {}s. "
                                "Increasing interval to {}s".format(int(checks_duration),
                                                                   self.config_check_secs,
                                                                   new_interval))
                    self.config_check_secs = new_interval

                time.sleep(self.config_check_secs)    
            
            except Exception:
                self.health = "{} Exception at {}".format(
                    sys.exc_info()[0].__name__,
                    datetime.strftime(datetime.now(),"%Y/%m/%d %H:%M:%S")
                )
                log.exception(self.health)
                break

        log.warning("Ceph configuration watcher stopped")


class Module(MgrModule):
    COMMANDS = [
        {
            "cmd": "k8sevents status",
            "desc": "Show the status of the data gathering threads",
            "perm": "r"
        },
        {
            "cmd": "k8sevents ls",
            "desc": "List all current Kuberenetes events from the Ceph namespace",
            "perm": "r"
        },
        {
            "cmd": "k8sevents ceph",
            "desc": "List Ceph events tracked & sent to the kubernetes cluster",
            "perm": "r"
        },
        {
            "cmd": "k8sevents set-access name=key,type=CephString",
            "desc": "Set kubernetes access credentials. <key> must be cacrt or token and use -i <filename> syntax (e.g., ceph k8sevents set-access cacrt -i /root/ca.crt).",
            "perm": "rw"
        },
        {
            "cmd": "k8sevents set-config name=key,type=CephString name=value,type=CephString",
            "desc": "Set kubernetes config paramters. <key> must be server or namespace (e.g., ceph k8sevents set-config server https://localhost:30433).",
            "perm": "rw"
        },
        {
            "cmd": "k8sevents clear-config",
            "desc": "Clear external kubernetes configuration settings",
            "perm": "rw"
        },
    ]
    MODULE_OPTIONS = [
        {'name': 'config_check_secs',
         'type': 'int',
         'default': 10,
         'min': 10,
         'desc': "interval (secs) to check for cluster configuration changes"},
        {'name': 'ceph_event_retention_days',
         'type': 'int',
         'default': 7,
         'desc': "Days to hold ceph event information within local cache"}
    ]
    NOTIFY_TYPES = [NotifyType.clog]

    def __init__(self, *args, **kwargs):
        self.run = True
        self.kubernetes_control = 'POD_NAME' in os.environ
        self.event_processor = None
        self.config_watcher = None
        self.ns_watcher = None
        self.trackers = list()
        self.error_msg = None
        self._api_client_config = None
        self._namespace = None
        
        # Declare the module options we accept
        self.config_check_secs = None
        self.ceph_event_retention_days = None

        self.k8s_config = dict(
            cacrt = None,
            token = None,
            server = None,
            namespace = None
        )

        super(Module, self).__init__(*args, **kwargs)

    def k8s_ready(self):
        """Validate the k8s_config dict 

        Returns:
         - bool .... indicating whether the config is ready to use
         - string .. variables that need to be defined before the module will function

        """
        missing = list()
        ready = True
        for k in self.k8s_config:
            if not self.k8s_config[k]:
                missing.append(k)
                ready = False
        return ready, missing

    def config_notify(self):
        """Apply runtime module options, and defaults from the modules KV store"""
        self.log.debug("applying runtime module option settings")
        for opt in self.MODULE_OPTIONS:
            setattr(self,
                    opt['name'],
                    self.get_module_option(opt['name']))

        if not self.kubernetes_control:
            # Populate the config
            self.log.debug("loading config from KV store")
            for k in self.k8s_config:
                self.k8s_config[k] = self.get_store(k, default=None)

    def fetch_events(self, limit=None):
        """Interface to expose current events to another mgr module"""
        # FUTURE: Implement this to provide k8s events to the dashboard?
        raise NotImplementedError

    def process_clog(self, log_message):
        """Add log message to the event queue
        
        :param log_message:     dict from the cluster log (audit/cluster channels)
        """
        required_fields = ['channel', 'message', 'priority', 'stamp']
        _message_attrs = log_message.keys()
        if all(_field in _message_attrs for _field in required_fields):
            self.log.debug("clog entry received - adding to the queue")
            if log_message.get('message').startswith('overall HEALTH'):
                m_type = 'heartbeat'
            else:
                m_type = log_message.get('channel')

            event_queue.put(
                LogEntry(
                    source='log',
                    msg_type=m_type,
                    msg=log_message.get('message'),
                    level=log_message.get('priority')[1:-1],
                    tstamp=log_message.get('stamp')
                )
            )
            
        else:
            self.log.warning("Unexpected clog message format received - skipped: {}".format(log_message))

    def notify(self, notify_type: NotifyType, notify_id):
        """
        Called by the ceph-mgr service to notify the Python plugin
        that new state is available.

        :param notify_type: string indicating what kind of notification,
                            such as osd_map, mon_map, fs_map, mon_status,
                            health, pg_summary, command, service_map
        :param notify_id:  string (may be empty) that optionally specifies
                            which entity is being notified about.  With
                            "command" notifications this is set to the tag
                            ``from send_command``.
        """
        
        # only interested in cluster log (clog) messages for now
        if notify_type == NotifyType.clog:
            self.log.debug("received a clog entry from mgr.notify")
            if isinstance(notify_id, dict):
                # create a log object to process
                self.process_clog(notify_id)
            else:
                self.log.warning("Expected a 'dict' log record format, received {}".format(type(notify_type)))

    def _show_events(self, events):

        max_msg_length = max([len(events[k].message) for k in events])
        fmt = "{:<20}  {:<8}  {:>5}  {:<" + str(max_msg_length) + "}  {}\n"
        s = fmt.format("Last Seen (UTC)", "Type", "Count", "Message", "Event Object Name")

        for event_name in sorted(events, 
                                 key = lambda name: events[name].last_timestamp,
                                 reverse=True):

            event = events[event_name]

            s += fmt.format(
                    datetime.strftime(event.last_timestamp,"%Y/%m/%d %H:%M:%S"),
                    str(event.type),
                    str(event.count),
                    str(event.message),
                    str(event_name)
            )
        s += "Total : {:>3}\n".format(len(events))
        return s

    def show_events(self, events):
        """Show events we're holding from the ceph namespace - most recent 1st"""

        if len(events):
            return 0, "", self._show_events(events)
        else:
            return 0, "", "No events emitted yet, local cache is empty"

    def show_status(self):
        s = "Kubernetes\n"
        s += "- Hostname  : {}\n".format(self.k8s_config['server'])
        s += "- Namespace : {}\n".format(self._namespace)
        s += "Tracker Health\n"
        for t in self.trackers:
            s += "- {:<20} : {}\n".format(t.__class__.__name__, t.health)
        s += "Tracked Events\n"
        s += "- namespace   : {:>3}\n".format(len(self.ns_watcher.events))
        s += "- ceph events : {:>3}\n".format(len(self.event_processor.events))
        return 0, "", s

    def _valid_server(self, server):
        # must be a valid server url format
        server = server.strip()

        res = urlparse(server)
        port = res.netloc.split(":")[-1]

        if res.scheme != 'https':
            return False, "Server URL must use https"

        elif not res.hostname:
            return False, "Invalid server URL format"

        elif res.hostname:
            try:
                socket.gethostbyname(res.hostname)
            except socket.gaierror:
                return False, "Unresolvable server URL"

        if not port.isdigit():
            return False, "Server URL must end in a port number"

        return True, ""

    def _valid_cacrt(self, cacrt_data):
        """use mgr_util.verify_cacrt to validate the CA file"""

        cacrt_fname = create_temp_file("ca_file", cacrt_data)

        try:
            verify_cacrt(cacrt_fname)
        except ServerConfigException as e:
            return False, "Invalid CA certificate: {}".format(str(e))
        else:
            return True, ""

    def _valid_token(self, token_data):
        """basic checks on the token"""
        if not token_data:
            return False, "Token file is empty"

        pattern = re.compile(r"[a-zA-Z0-9\-\.\_]+$")
        if not pattern.match(token_data):
            return False, "Token contains invalid characters"

        return True, ""

    def _valid_namespace(self, namespace):
        # Simple check - name must be a string <= 253 in length, alphanumeric with '.' and '-' symbols

        if len(namespace) > 253:
            return False, "Name too long"
        if namespace.isdigit():
            return False, "Invalid name - must be alphanumeric"

        pattern = re.compile(r"^[a-z][a-z0-9\-\.]+$")
        if not pattern.match(namespace):
            return False, "Invalid characters in the name"
        
        return True, ""

    def _config_set(self, key, val):
        """Attempt to validate the content, then save to KV store"""

        val = val.rstrip()                      # remove any trailing whitespace/newline 

        try:
            checker = getattr(self, "_valid_" + key)
        except AttributeError:
            # no checker available, just let it pass
            self.log.warning("Unable to validate '{}' parameter - checker not implemented".format(key))
            valid = True
        else:
            valid, reason = checker(val)

        if valid:
            self.set_store(key, val)
            self.log.info("Updated config KV Store item: " + key)
            return 0, "", "Config updated for parameter '{}'".format(key)
        else:
            return -22, "", "Invalid value for '{}' :{}".format(key, reason)

    def clear_config_settings(self):
        for k in self.k8s_config:
            self.set_store(k, None)
        return 0,"","{} configuration keys removed".format(len(self.k8s_config.keys()))

    def handle_command(self, inbuf, cmd):

        access_options = ['cacrt', 'token']
        config_options = ['server', 'namespace']

        if cmd['prefix'] == 'k8sevents clear-config':
            return self.clear_config_settings()
        
        if cmd['prefix'] == 'k8sevents set-access':
            if cmd['key'] not in access_options:
                return -errno.EINVAL, "", "Unknown access option. Must be one of; {}".format(','.join(access_options))

            if inbuf:
                return self._config_set(cmd['key'], inbuf)
            else:
                return -errno.EINVAL, "", "Command must specify -i <filename>"

        if cmd['prefix'] == 'k8sevents set-config':

            if cmd['key'] not in config_options:
                return -errno.EINVAL, "", "Unknown config option. Must be one of; {}".format(','.join(config_options))

            return self._config_set(cmd['key'], cmd['value'])

        # At this point the command is trying to interact with k8sevents, so intercept if the configuration is 
        # not ready
        if self.error_msg:
            _msg = "k8sevents unavailable: " + self.error_msg
            ready, _ = self.k8s_ready()
            if not self.kubernetes_control and not ready:
                _msg += "\nOnce all variables have been defined, you must restart the k8sevents module for the changes to take effect"
            return -errno.ENODATA, "", _msg

        if cmd["prefix"] == "k8sevents status":
            return self.show_status()

        elif cmd["prefix"] == "k8sevents ls":
            return self.show_events(self.ns_watcher.events)

        elif cmd["prefix"] == "k8sevents ceph":
            return self.show_events(self.event_processor.events)

        else:
            raise NotImplementedError(cmd["prefix"])

    @staticmethod
    def can_run():
        """Determine whether the pre-reqs for the module are in place"""

        if not kubernetes_imported:
            return False, "kubernetes python client is not available"
        return True, ""

    def load_kubernetes_config(self):
        """Load configuration for remote kubernetes API using KV store values

        Attempt to create an API client configuration from settings stored in 
        KV store.

        Returns:
        client.ApiClient: kubernetes API client object

        Raises:
        OSError: unable to create the cacrt file
        """

        # the kubernetes setting Configuration.ssl_ca_cert is a path, so we have to create a 
        # temporary file containing the cert for the client to load from
        try:
            ca_crt_file = create_temp_file('cacrt', self.k8s_config['cacrt'])
        except OSError as e:
            self.log.error("Unable to create file to hold cacrt: {}".format(str(e)))
            raise OSError(str(e))
        else:
            self.log.debug("CA certificate from KV store, written to {}".format(ca_crt_file))

        configuration = client.Configuration()
        configuration.host = self.k8s_config['server']
        configuration.ssl_ca_cert = ca_crt_file
        configuration.api_key = { "authorization": "Bearer " + self.k8s_config['token'] }
        api_client = client.ApiClient(configuration)
        self.log.info("API client created for remote kubernetes access using cacrt and token from KV store")

        return api_client

    def serve(self):
        # apply options set by CLI to this module
        self.config_notify()

        if not kubernetes_imported:
            self.error_msg = "Unable to start : python kubernetes package is missing"
        else:
            if self.kubernetes_control:
                # running under rook-ceph
                config.load_incluster_config()
                self.k8s_config['server'] = "https://{}:{}".format(os.environ.get('KUBERNETES_SERVICE_HOST', 'UNKNOWN'),
                                                                   os.environ.get('KUBERNETES_SERVICE_PORT_HTTPS', 'UNKNOWN'))
                self._api_client_config = None
                self._namespace = os.environ.get("POD_NAMESPACE", "rook-ceph")
            else:
                # running outside of rook-ceph, so we need additional settings to tell us
                # how to connect to the kubernetes cluster
                ready, errors = self.k8s_ready()
                if not ready:
                    self.error_msg = "Required settings missing. Use ceph k8sevents set-access | set-config to define {}".format(",".join(errors))
                else:
                    try:
                        self._api_client_config = self.load_kubernetes_config()
                    except OSError as e:
                        self.error_msg = str(e)
                    else:
                        self._namespace = self.k8s_config['namespace']
                        self.log.info("k8sevents configuration loaded from KV store")

        if self.error_msg:
            self.log.error(self.error_msg)
            return

        # All checks have passed
        self.config_watcher = CephConfigWatcher(self)

        self.event_processor = EventProcessor(self.config_watcher, 
                                              self.ceph_event_retention_days,
                                              self._api_client_config,
                                              self._namespace)

        self.ns_watcher = NamespaceWatcher(api_client_config=self._api_client_config, 
                                           namespace=self._namespace)

        if self.event_processor.ok:
            log.info("Ceph Log processor thread starting")
            self.event_processor.start()        # start log consumer thread
            log.info("Ceph config watcher thread starting")
            self.config_watcher.start()
            log.info("Rook-ceph namespace events watcher starting")
            self.ns_watcher.start()

            self.trackers.extend([self.event_processor, self.config_watcher, self.ns_watcher])
            
            while True:
                # stay alive
                time.sleep(1)

                trackers = self.trackers
                for t in trackers:
                    if not t.is_alive() and not t.reported:
                        log.error("K8sevents tracker thread '{}' stopped: {}".format(t.__class__.__name__, t.health))
                        t.reported = True

        else:
            self.error_msg = "Unable to access kubernetes API. Is it accessible? Are RBAC rules for our token valid?"
            log.warning(self.error_msg)
            log.warning("k8sevents module exiting")
            self.run = False

    def shutdown(self):
        self.run = False
        log.info("Shutting down k8sevents module")
        self.event_processor.can_run = False

        if self._rados:
            self._rados.shutdown()
