Heavily borrow EMDR code for a relay.

src/eddn/Relay.py

@@ -0,0 +1,58 @@
+"""
+Relays sit below an announcer, or another relay, and simply repeat what
+they receive over PUB/SUB.
+"""
+# Logging has to be configured first before we do anything.
+import logging
+
+logger = logging.getLogger(__name__)
+import zlib
+
+import gevent
+import zmq.green as zmq
+from eddn.conf import Settings
+
+
+def run():
+    """
+    Fires up the relay process.
+    """
+    # These form the connection to the Gateway daemon(s) upstream.
+    context = zmq.Context()
+
+    receiver = context.socket(zmq.SUB)
+    receiver.setsockopt(zmq.SUBSCRIBE, '')
+    for binding in Settings.RELAY_RECEIVER_BINDINGS:
+        # Relays bind upstream to an Announcer, or another Relay.
+        receiver.connect(binding)
+
+    sender = context.socket(zmq.PUB)
+    for binding in Settings.RELAY_SENDER_BINDINGS:
+        # End users, or other relays, may attach here.
+        sender.bind(binding)
+
+    def relay_worker(message):
+        """
+        This is the worker function that re-sends the incoming messages out
+        to any subscribers.
+        :param str message: A JSON string to re-broadcast.
+        """
+        # if is_message_duped(message):
+            # We've already seen this message recently. Discard it.
+        #    return
+
+        if Settings.RELAY_DECOMPRESS_MESSAGES:
+            message = zlib.decompress(message)
+
+        sender.send(message)
+
+    logger.info("Relay is now listening for order data.")
+
+    while True:
+        # For each incoming message, spawn a greenlet using the relay_worker
+        # function.
+        gevent.spawn(relay_worker, receiver.recv())
+
+
+if __name__ == '__main__':
+    run()

src/eddn/conf/Settings.py

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+'''
+Created on 15 Nov 2014
+
+@author: james
+'''
+
+RELAY_RECEIVER_BINDINGS = ["tcp://*:8500"]
+
+RELAY_SENDER_BINDINGS = ["tcp://*:9500"]
+
+RELAY_DECOMPRESS_MESSAGES = False