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# Copyright 2019, Battelle Memorial Institute.
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from contextlib import closing
from zmq import green as zmq
from volttron.platform import jsonapi
from . import Core, ZMQCore, RPC, PeerList, PubSub
from .subsystems.pubsub import encode_peer
from volttron.platform.messaging.headers import Headers
[docs]class CompatPubSub(object):
'''VOLTTRON 2.x compatible agent pub/sub message exchange bus.
Accept multi-part messages from sockets connected to in_addr, which
is a PULL socket, and forward them to sockets connected to out_addr,
which is a XPUB socket. When subscriptions are added or removed, a
message of the form 'subscriptions/<OP>/<TOPIC>' is broadcast to the
PUB socket where <OP> is either 'add' or 'remove' and <TOPIC> is the
topic being subscribed or unsubscribed. When a message is received
of the form 'subscriptions/list/<PREFIX>', a multipart message will
be broadcast with the first two received frames (topic and headers)
sent unchanged and with the remainder of the message containing
currently subscribed topics which start with <PREFIX>, each frame
containing exactly one topic.
'''
PEER = b'pubsub'
PUBLISH_ADDRESS = 'inproc://vip/compat/agent/publish'
SUBSCRIBE_ADDRESS = 'inproc://vip/compat/agent/subscribe'
def __init__(self, identity=None, address=None, context=None, peer=PEER,
publish_address=PUBLISH_ADDRESS,
subscribe_address=SUBSCRIBE_ADDRESS,
message_bus='zmq'):
self.core = ZMQCore(
self, identity=identity, address=address, context=context)
self.rpc = RPC(self.core, self)
self.peerlist = PeerList(self.core)
self.pubsub = PubSub(self.core, self.rpc, self.peerlist, self)
self.peer = peer
self.publish_address = publish_address
self.subscribe_address = subscribe_address
self.in_sock = None
self.out_sock = None
[docs] @Core.receiver('onsetup')
def setup(self, sender, **kwargs):
self.in_sock = zmq.Socket(self.core.context, zmq.PULL)
self.out_sock = zmq.Socket(self.core.context, zmq.XPUB)
[docs] @Core.receiver('onstart')
def in_loop(self, sender, **kwargs): # pylint: disable=unused-argument
peer = self.peer
with closing(self.in_sock) as sock:
sock.bind(self.publish_address)
while True:
message = sock.recv_multipart()
#log.debug('incoming message: {!r}'.format(message))
topic = message[0]
if (topic.startswith('subscriptions/list') and
topic[18:19] in ['/', '']):
if len(message) > 2:
del message[2:]
elif len(message) == 1:
message.append('')
prefix = topic[19:].decode('utf-8')
topics = self.pubsub.list(
peer, prefix, subscribed=False).get()
message.extend(topic.encode('utf-8')
for _, topic, _ in topics)
self.out_sock.send_multipart(message)
else:
message = [part.decode('utf-8') for part in message]
try:
topic, headers = message[:2]
except (ValueError, TypeError):
continue
headers = jsonapi.loads(headers)
message = message[2:]
self.pubsub.publish(peer, topic, headers, message).get()
[docs] @Core.receiver('onstart')
def out_loop(self, sender, **kwargs): # pylint: disable=unused-argument
peer = self.peer
with closing(self.out_sock) as sock:
sock.bind(self.subscribe_address)
while True:
message = sock.recv()
if message:
add = bool(ord(message[0]))
topic = message[1:].decode('utf-8')
if add:
self.pubsub.subscribe(peer, topic, self.forward).get()
else:
self.pubsub.unsubscribe(peer, topic, self.forward).get()
#log.debug('incoming subscription: {} {!r}'.format(
# ('add' if add else 'remove'), topic))
sock.send('subscriptions/{}{}{}'.format(
('add' if add else 'remove'),
('' if topic[:1] == '/' else '/'), topic))
[docs] def forward(self, peer, sender, bus, topic, headers, message):
headers = Headers(headers)
headers['VIP.peer'] = encode_peer(peer)
headers['VIP.sender'] = encode_peer(sender)
headers['VIP.bus'] = bus
parts = [topic]
if message is not None:
if 'Content-Type' in headers:
if isinstance(message, list):
parts.extend(message)
else:
parts.append(message)
else:
parts.append(jsonapi.dumps(message))
headers['Content-Type'] = 'application/json'
parts.insert(1, jsonapi.dumps(headers.dict))
self.out_sock.send_multipart(parts)
[docs]def unpack_legacy_message(headers, message):
'''Unpack legacy pubsub messages for VIP agents.
Loads JSON-formatted message parts and removes single-frame messages
from their containing list. Does not alter headers.
'''
if not isinstance(headers, Headers):
headers = Headers(headers)
try:
content_type = headers['Content-Type']
except KeyError:
return headers, message
if isinstance(content_type, str):
if content_type.lower() == 'application/json':
if isinstance(message, list) and len(message) == 1:
return jsonapi.loads(message[0])
if isinstance(message, str):
return jsonapi.loads(message)
if isinstance(message, list) and len(message) == 1:
return message[0]
if isinstance(content_type, list) and isinstance(message, list):
parts = [(jsonapi.loads(msg)
if str(ctype).lower() == 'application/json' else msg)
for ctype, msg in zip(content_type, message)]
parts.extend(message[len(parts):])
if len(parts) == len(content_type) == 1:
return parts[0]
return parts
return message