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POA distributed algorithm to assign a shared resource to one node out of many
 

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  1. POA distributed algorithm to assign a shared resource to one node out of many
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    <p>I try to implement a multicast communication to distribute some resources. I’m using <a href="http://www.jgroups.org/" rel="nofollow">jGroups</a> for that, so I have reliable multicast and FIFO-Ordering. By doing that I wanna realise that with a distributed solution, that means without an master node that acts as a coordinator. </p> <p>Every node is able to start a distribution, so it is possible that two or more nodes are starting the distribution at the same time. When a node receives a distribution-message it will answer this. There are no differences between an answer-message and a message from a starter. It only contains information about the resource-name (e.g. resourceA) and if that node is able to handle it. When Member1 starting the distribution it will send a message like: </p> <pre><code>Member1, resourceA, OK </code></pre> <p>Member2 has no space for that resource and send a answer-message like:</p> <pre><code>Member2, resourceA, NOT_OK </code></pre> <p>In this case it is easy, because now Member1 knows that he can takes resourceA. When more than one node are able to handle the resource other properties will decide who takes the resource (e.g. the member with the highest ID). </p> <p>My problem is: How ta handle it when two or more nodes are starting the distribution about the same topic (resourceA) at the same time?</p> <p>Does anybody see some problems doing it this way: Member1 and Member2 are starting the distribution at the same time. At this point both are expecting a response from each other. Because of the fact that there are no differences in a response-message or in a starter-message both are thinking the message they just received is an answerer. So Member1 sends a starter-message into the multicast-group and Member2 sends a starter-message into the mutlicast-group (before receiving the message from Member1). Now Member1 is receiving the starter-message from Member2 and thinks that this is the response.</p> <p>By guarantee that every node sends only one message per topic (as a starter or with a response) I would say that there are no problems doing it this way even when there are more than two nodes.</p>
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    1. USReinier Torenbeek
    1. USstormsam
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    1. COHow about making those request and ack messages different? Is there a reason they have to be the same?
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      1. POA distributed algorithm to assign a shared resource to one node out of many
      1. USNikolai Fetissov
    2. COBy using different kinds of messages I will need a collision detection. Because it could happen that Member1 starts a distribution of resourceA and at the same time Member2 starts the same distribution. Member3 sends a answer to Member1 and Member4 sends a answer to Member2. Now Member3 is receiving the message of Member2 and has to detect the collision. After that he has to send a abort-message to everyone. It would be more complicated.
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      1. USstormsam
 

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