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<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">That’s what I thought as well, although I’m thinking about a couple of issues about it:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span lang="EN-US" style="font-family:Symbol;color:#1F497D"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-US" style="color:#1F497D">Lack of knowledge about Erlang, which is the language I’d have to use to build a custom exchange, I guess<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span lang="EN-US" style="font-family:Symbol;color:#1F497D"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-US" style="color:#1F497D">Amount of memory it would require to store the entire history in memory. It needn’t be in memory actually, but I’m not sure what would be the recommended way if the storage has to be carried
out by exchange itself. Mnesia perhaps, would it make sense?<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif";mso-fareast-language:IT">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif";mso-fareast-language:IT"> Jon Brisbin
[mailto:jon@jbrisbin.com] <br>
<b>Sent:</b> Wednesday, June 01, 2011 3:38 PM<br>
<b>To:</b> Busoli, Simone<br>
<b>Cc:</b> rabbitmq-discuss@lists.rabbitmq.com<br>
<b>Subject:</b> Re: [rabbitmq-discuss] How to handle full exchange history delivery<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="color:black">I've been seriously considering adding this functionality to the Riak-backed custom exchange. It was something I thought I would add first time through but didn't.<br>
<br>
You'd have to use a custom exchange. Not sure if that's an issue in your scenario or not.<br>
<br>
<br>
Thanks!<br>
<br>
Jon Brisbin<br>
http//jbrisbin.com<br>
<br>
<o:p></o:p></span></p>
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<blockquote style="border:none;border-left:solid #1010FF 1.5pt;padding:0in 0in 0in 4.0pt;margin-left:3.75pt;margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><b><span style="font-family:"Helvetica","sans-serif";color:black">From:
</span></b><span style="font-family:"Helvetica","sans-serif";color:black">"Simone Busoli" <Simone.Busoli@ferrari.com><br>
<b>To: </b>rabbitmq-discuss@lists.rabbitmq.com<br>
<b>Sent: </b>Wednesday, June 1, 2011 5:52:24 AM<br>
<b>Subject: </b>[rabbitmq-discuss] How to handle full exchange history delivery<br>
<br>
<br>
</span><span style="font-size:12.0pt;font-family:"Helvetica","sans-serif";color:black;mso-fareast-language:IT"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:black">I am trying to achieve a scenario in which messages are published from some data source into a RabbitMQ exchange and clients should be able to receive the full history of messages flown through that
exchange, regardless of the exact moment in time when they connect.</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:black">I’ve been thinking to solve it by setting up a proxy which subscribes to the exchange where messages are published using its own queue, keeps an internal storage of the messages and accepts requests
from clients. </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:black">When a request from a client arrives it just replays the full message history to the client by publishing the messages to the client queue (supplied in the ReplyTo field),
<b>then</b> binds the client queue to the messages exchange, so that the client from this moment onwards starts receiving the “live” messages, and is pretty much unaware of what’s happened; it simply just receives the whole history.</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:black">Now I am under the impression that there’s a fundamental flaw in this reasoning, since the proxy cannot know when the message history has completed and he can switch the client to the live stream,
because while it is replaying historical messages to the client other live messages might be arriving on the proxy’s queue, thus getting into an endless loop.</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:black">I’m probably missing something obvious, any advice about how others would approach this scenario is appreciated.</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:black">Simone</span><span style="color:black"><o:p></o:p></span></p>
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