[nanomsg] Broadcast protocol
- From: Paul Colomiets <paul@xxxxxxxxxxxxxx>
- To: nanomsg@xxxxxxxxxxxxx
- Date: Wed, 11 Sep 2013 16:13:22 +0300
Hi,
I would like to propose a new protocol for nanomsg. I call it "broadcast"
just so we have some name to discuss. Better name is appreciated.
Overview
--------------
I may define the protocol with the following:
1. There are many watchers
2. Watcher subscribes to a channel at the start
3. When subscribing watcher gets current data on a channel
4. When channel data changes, all its watchers get new value
Combination of pubsub and reqrep can't be used here, because when pubsub
temporarily disconnects some updates can be lost.
API
-----
There are two endpoints: WATCHER and BROADCASTER
The WATCHER (pseudocode, probably python):
sock = nn_socket(AF_SP, NN_WATCHER)
sock.send("channel:foo") # subscription
while True:
print(sock.recv()) # receives updated value
sock.send("channel:bar") # cancel's previous subscription
The BROADCASTER:
sock = nn_socket(AF_SP, NN_BROADCASTER)
while True:
sub = sock.recv() # get subscription request from watcher
_literal, channel = sub.split(':')
assert _literal == 'channel'
sock.send(channel + '\0' + data[channel], 0)
# probably in another thread
data['foo'] = 'newvalue'
sock.send('foo' + '\0' + 'newvalue', NN_BROADCAST)
Important points are:
1. Request is different from the channel that watcher would be subscribed to
2. NN_BROADCAST flag says that message is not a reply but a broadcast
message
To keep message short I do not discuss all the apparent issues, just asking
for general agreement.
Thoughts?
P.S.: This protocol is result of discussion of the name service. I hope we
will return back through the "monitoring data -> name service -> broadcast
proto" chain shortly :)
--
Paul
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