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Date: Thu, 08 Sep 2011 18:15:50 +1000
From: Steve <shadders.del@gmail.com>
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To: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
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Subject: Re: [Bitcoin-development] bitcoind multiplexing proxy -
 request/response routing problem
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Reply-To: shadders.del@gmail.com

4a/ Serialize all request/response exchanges.  i.e. request comes in 
from remote node, proxy aquires lock on the proxy-localdaemon channel 
and sends request.  Channel remains locked until response is received or 
timeout (in which case remote node gets no response).  Unlock channel 
after response received and send to client.

Possibly messages that don't expect a response (e.g. relaying a tx 
broadcast from remote node) can be pushed down a locked channel to 
improve performance as they won't interfere with sequencing.  Locked 
channels may also receive other unsolicited messages from local daemon 
before the expected response message which would be dealt with the same 
as if they came from an unlocked channel.

Disadvantages:  Idle time for channel while waiting for response.  As 
per option 2 this allows the proxy to stay dumb/thin but loses 
opportunity for de-duplicating/caching unless option 1 is layered on top.

4b/ As per 4a but use all 125 available bitcoind connections in a 
channel pool.  Acquiring a lock on a channel consists of checking for an 
unlocked channel first then waiting in a queue for one to become available.