Adds basic ChainMonitor to the system

ChainMonitor is the actor in charge of checking new blocks. It improves from the previous zmq_subscriber by also doing polling and, therefore, making sure that no blocks are missed.

Documentation and tests are still required. Partially covers #31

pisa/utils/zmq_subscriber.py

@@ -1,34 +0,0 @@
-import zmq
-import binascii
-from common.logger import Logger
-from pisa.conf import FEED_PROTOCOL, FEED_ADDR, FEED_PORT
-
-
-# ToDo: #7-add-async-back-to-zmq
-class ZMQSubscriber:
-    """ Adapted from https://github.com/bitcoin/bitcoin/blob/master/contrib/zmq/zmq_sub.py"""
-
-    def __init__(self, parent):
-        self.zmqContext = zmq.Context()
-        self.zmqSubSocket = self.zmqContext.socket(zmq.SUB)
-        self.zmqSubSocket.setsockopt(zmq.RCVHWM, 0)
-        self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "hashblock")
-        self.zmqSubSocket.connect("%s://%s:%s" % (FEED_PROTOCOL, FEED_ADDR, FEED_PORT))
-        self.logger = Logger("ZMQSubscriber-{}".format(parent))
-
-        self.terminate = False
-
-    def handle(self, block_queue):
-        while not self.terminate:
-            msg = self.zmqSubSocket.recv_multipart()
-
-            # Terminate could have been set wile the thread was blocked in recv
-            if not self.terminate:
-                topic = msg[0]
-                body = msg[1]
-
-                if topic == b"hashblock":
-                    block_hash = binascii.hexlify(body).decode("utf-8")
-                    block_queue.put(block_hash)
-
-                    self.logger.info("New block received via ZMQ", block_hash=block_hash)