"""Bridge client side plugins to the C{MessageExchange}.

The C{BrokerServer} provides C{BrokerClient}s with a mechanism to send messages
to the server and, likewise, triggers those plugins to take action when a
exchange is impending or resynchronisaton is required.

Each C{BrokerClient} has to be registered using the
L{BrokerServer.register_client} method, after which two way communications is
possible between the C{BrokerServer} and the C{BrokerClient}.

Resynchronisation Sequence
==========================

See L{landscape.broker.exchange} sequence diagram for origin of the
"resynchronize-clients" event.

Diagram::


1. [event 1] ---> BrokerServer : Event
: "resynchronize-clients"

2. [event 2] <--- BrokerServer : Broadcast event
: "resynchronize"

3. [optional: various L{BrowserClientPlugin}s respond
to the "resynchronize" event to reset
themselves and start report afresh.]
(See: L{landscape.monitor.packagemonitor.PackageMonitor}
L{landscape.monitor.plugin.MonitorPlugin}
L{landscape.manager.keystonetoken.KeystoneToken}
L{landscape.monitor.activeprocessinfo.ActiveProcessInfo} )


4. [event 1] ---> MessageExchange : Event
(NOTE, this is the same event as step 1 : "resynchronize-clients"
it is handled by both BrokerServer and
MessageExchange.
See MessageExchange._resynchronize )

5. MessageExchange ---> MessageExchange : Schedule urgent
: exchange

"""

import logging

from twisted.internet.defer import Deferred

from landscape.lib.twisted_util import gather_results
from landscape.amp import remote
from landscape.manager.manager import FAILED


def event(method):
"""Turns a L{BrokerServer} method into an event broadcaster.

When the decorated method is called, an event is fired on all connected
clients. The event will have the same name as the method being called,
except that any underscore in the method name will be replaced with a dash.
"""
event_type = method.__name__.replace("_", "-")

def broadcast_event(self, *args, **kwargs):
fired = []
for client in self.get_clients():
fired.append(client.fire_event(event_type, *args, **kwargs))
return gather_results(fired)

return broadcast_event


class BrokerServer(object):
"""
A broker server capable of handling messages from plugins connected using
the L{BrokerProtocol}.

@param config: The L{BrokerConfiguration} used by the broker.
@param reactor: The L{LandscapeReactor} driving the broker's events.
@param exchange: The L{MessageExchange} to send messages with.
@param registration: The {RegistrationHandler}.
@param message_store: The broker's L{MessageStore}.
"""
name = "broker"

def __init__(self, config, reactor, exchange, registration,
message_store, pinger):
from landscape.broker.amp import get_component_registry
self.connectors_registry = get_component_registry()
self._config = config
self._reactor = reactor
self._exchanger = exchange
self._registration = registration
self._message_store = message_store
self._registered_clients = {}
self._connectors = {}
self._pinger = pinger

reactor.call_on("message", self.broadcast_message)
reactor.call_on("impending-exchange", self.impending_exchange)
reactor.call_on("message-type-acceptance-changed",
self.message_type_acceptance_changed)
reactor.call_on("server-uuid-changed", self.server_uuid_changed)
reactor.call_on("package-data-changed", self.package_data_changed)
reactor.call_on("resynchronize-clients", self.resynchronize)

@remote
def ping(self):
"""Return C{True}."""
return True

@remote
def get_session_id(self, scope=None):
"""Get a unique session ID to be used when sending messages.

Anything that wants to send a message to the server via the broker is
required to first acquire a session ID with this method. Such session
IDs must be passed to L{send_message} whenever sending a message.

The broker keeps track of the session IDs that it hands out and will
drop them when a re-synchronisation event occurs. Further messages
sent using expired IDs will be silently discarded.

For example each L{BrokerClientPlugin} calls this method to get a
session ID and use it when sending messages, until the plugin gets
notified of a re-synchronisation event and then asks for a new one.

This eliminates issues with out-of-date messages being delivered to the
server after a re-synchronisation request. For example when the client
re-registers and gets a new computer ID we don't want to deliver
messages containing references to activity IDs of the old computer
(e.g. a message with the result of a "change-packages" activity
delivered before re-registering). See also #328005 and #1158822.

"""
return self._message_store.get_session_id(scope=scope)

@remote
def register_client(self, name):
"""Register a broker client called C{name}.

Various broker clients interact with the broker server, such as the
monitor for example, using the L{BrokerServerConnector} for performing
remote method calls on the L{BrokerServer}.

They establish connectivity with the broker by connecting and
registering themselves, the L{BrokerServer} will in turn connect
to them in order to be able to perform remote method calls like
broadcasting events and messages.

@param name: The name of the client, such a C{monitor} or C{manager}.
"""
connector_class = self.connectors_registry.get(name)
connector = connector_class(self._reactor, self._config)

def register(remote_client):
self._registered_clients[name] = remote_client
self._connectors[remote_client] = connector

connected = connector.connect()
return connected.addCallback(register)

def get_clients(self):
"""Get L{RemoteClient} instances for registered clients."""
return self._registered_clients.values()

def get_client(self, name):
"""Return the client with the given C{name} or C{None}."""
return self._registered_clients.get(name)

def get_connectors(self):
"""Get connectors for registered clients.

@see L{RemoteLandscapeComponentCreator}.
"""
return self._connectors.values()

def get_connector(self, name):
"""Return the connector for the given C{name} or C{None}."""
return self._connectors.get(self.get_client(name))

@remote
def send_message(self, message, session_id, urgent=False):
"""Queue C{message} for delivery to the server at the next exchange.

@param message: The message C{dict} to send to the server. It must
have a C{type} key and be compatible with C{landscape.lib.bpickle}.
@param session_id: A session ID. You should acquire this
with C{get_session_id} before attempting to send a message.
@param urgent: If C{True}, exchange urgently, otherwise exchange
during the next regularly scheduled exchange.
@return: The message identifier created when queuing C{message}.
"""
if session_id is None:
raise RuntimeError(
"Session ID must be set before attempting to send a message")
if self._message_store.is_valid_session_id(session_id):
return self._exchanger.send(message, urgent=urgent)

@remote
def is_message_pending(self, message_id):
"""Indicate if a message with given C{message_id} is pending."""
return self._message_store.is_pending(message_id)

@remote
def stop_clients(self):
"""Tell all the clients to exit."""
results = []
# FIXME: check whether the client are still alive
for client in self.get_clients():
results.append(client.exit())
result = gather_results(results, consume_errors=True)
return result.addCallback(lambda ignored: None)

@remote
def reload_configuration(self):
"""Reload the configuration file, and stop all clients."""
self._config.reload()
# Now we'll kill off everything else so that they can be restarted and
# notice configuration changes.
return self.stop_clients()

@remote
def register(self):
"""Attempt to register with the Landscape server.

@see: L{RegistrationHandler.register}
"""
return self._registration.register()

@remote
def get_accepted_message_types(self):
"""Return the message types accepted by the Landscape server."""
return self._message_store.get_accepted_types()

@remote
def get_server_uuid(self):
"""Return the uuid of the Landscape server we're pointing at."""
return self._message_store.get_server_uuid()

@remote
def register_client_accepted_message_type(self, type):
"""Register a new message type which can be accepted by this client.

@param type: The message type to accept.
"""
self._exchanger.register_client_accepted_message_type(type)

@remote
def fire_event(self, event_type):
"""Fire an event in the broker reactor."""
self._reactor.fire(event_type)

@remote
def exit(self):
"""Request a graceful exit from the broker server.

Before this method returns, all broker clients will be notified
of the server broker's intention of exiting, so that they have
the chance to stop whatever they're doing in a graceful way, and
then exit themselves.

This method will only return a result when all plugins returned
their own results.
"""
clients_stopped = self.stop_clients()

def schedule_reactor_stop(ignored):
# Stop the reactor with a short delay to give us a chance to reply
# to the caller when this method is invoked over AMP (typically
# by the watchdog, see landscape.watchdog.Watchdog.request_exit).
#
# Note that stopping the reactor will cause the Twisted machinery
# to invoke BrokerService.stopService, which in turn will stop the
# exchanger/pinger and cleanly close all AMP sockets.
self._reactor.call_later(1, lambda: self._reactor.stop())

return clients_stopped.addBoth(schedule_reactor_stop)

@event
def resynchronize(self):
"""Broadcast a C{resynchronize} event to the clients."""

@event
def impending_exchange(self):
"""Broadcast an C{impending-exchange} event to the clients."""

@remote
def listen_events(self, event_types):
"""
Return a C{Deferred} that fires when the first event occurs among the
given ones.
"""
deferred = Deferred()
calls = []

def get_handler(event_type):

def handler():
for call in calls:
self._reactor.cancel_call(call)
deferred.callback(event_type)

return handler

for event_type in event_types:
call = self._reactor.call_on(event_type, get_handler(event_type))
calls.append(call)
return deferred

@event
def broker_reconnect(self):
"""Broadcast a C{broker-reconnect} event to the clients."""

@event
def server_uuid_changed(self, old_uuid, new_uuid):
"""Broadcast a C{server-uuid-changed} event to the clients."""

@event
def message_type_acceptance_changed(self, type, accepted):
pass

@event
def package_data_changed(self):
"""Fire a package-data-changed event in the reactor of each client."""

def broadcast_message(self, message):
"""Call the C{message} method of all the registered plugins.

@see: L{register_plugin}.
"""
results = []
for client in self.get_clients():
results.append(client.message(message))
result = gather_results(results)
return result.addCallback(self._message_delivered, message)

def _message_delivered(self, results, message):
"""
If the message wasn't handled, and it's an operation request (i.e. it
has an operation-id), then respond with a failing operation result
indicating as such.
"""
opid = message.get("operation-id")
if (True not in results
and opid is not None
and message["type"] != "resynchronize"):
mtype = message["type"]
logging.error("Nobody handled the %s message." % (mtype,))

result_text = """\
Landscape client failed to handle this request (%s) because the
plugin which should handle it isn't available. This could mean that the
plugin has been intentionally disabled, or that the client isn't running
properly, or you may be running an older version of the client that doesn't
support this feature.
""" % (mtype,)
response = {
"type": "operation-result",
"status": FAILED,
"result-text": result_text,
"operation-id": opid}
self._exchanger.send(response, urgent=True)

@remote
def stop_exchanger(self):
"""
Stop exchaging messages with the message server.

Eventually, it is required by the plugin that no more message exchanges
are performed.
For example, when a reboot process in running, the client stops
accepting new messages so that no client action is running while the
machine is rebooting.
Also, some activities should be explicitly require that no more
messages are exchanged so some level of serialization in the client
could be achieved.
"""
self._exchanger.stop()
self._pinger.stop()