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https://issues.apache.org/jira/browse/IGNITE-4501?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15968139#comment-15968139
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Alexander Menshikov commented on IGNITE-4501:
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[~yzhdanov]
I understand what going on. Region ID breaks optimization in
ServerImpl.RingMessageWorker#processNodeAddedMessage() which clears discovery
data from TcpDiscoveryNodeAddedMessage in case when new node is sending
TcpDiscoveryJoinRequestMessage to coordinator. Because after that if new node
take a random position in the ring and then coordinator verifies it and sends
verified message through the ring, but new node not in the end of the ring.
This optimization clears data from message and the next nodes get NPE when try
to get data.
> Improvement of connection in a cluster of new node
> --------------------------------------------------
>
> Key: IGNITE-4501
> URL: https://issues.apache.org/jira/browse/IGNITE-4501
> Project: Ignite
> Issue Type: Improvement
> Components: messaging
> Affects Versions: 1.8
> Reporter: Vyacheslav Daradur
> Assignee: Alexander Menshikov
> Fix For: 2.0
>
>
> h3. Main description:
> Cluster nodes connect a ring.
> For example: we have 6 nodes: A, B, C, D, E, F.
> They can connect a ring in any possible way: A-B-C-D-E-F-A, or A-F-B-E-C-D-A,
> etc.
> If some node leaves topology, adjacent nodes must reconnect.
> If nodes A, B, C are in same physical place, nodes D, E, F are in other
> place, and places lost connect each other, we will have many ways of
> reconnections.
> At best case, if we had a ring: A-B-CxD-E-FxA ('x' means disconnect) -- then
> we have only one reconnect (C
> will be connected to A or F will be connected to D -- depends on what part of
> the cluster was alive.
> Also, if we had a not ring: AxFxBxExCxDxA -- then we have a lot of
> reconnections (A to B, B to C, C to A -- in general n/2 reconnections, where
> n -- number of nodes).
> h3. Approach:
> It is necessary to develop approach of node insertion to the correct place
> for creation of the correct ring-topology.
> h3. Solutions:
> Main idea is a sorting according to latency.
> * group nodes in arcs on an ARC_ID. (manualy?)
> * implement NodeComparator (nodes on the same host : nodes on the same subnet
> : other nodes). We will use it when we connect a new node.
> * [dev list
> thread|http://mail-archives.apache.org/mod_mbox/ignite-dev/201612.mbox/%3CCAN+WSNyWYXSXEBpGErVt72zTgi2pTQzUWLv8JY=ke83-5-r...@mail.gmail.com%3E]
> Update Dec, 29 Yakov Zhdanov:
> # introduce CLUSTER_REGION_ID node attribute. This can be done by adding
> public static final constant to TcpDiscoverySpi.
> # Alter
> org.apache.ignite.spi.discovery.tcp.internal.TcpDiscoveryNodesRing#nextNode(java.util.Collection<org.apache.ignite.spi.discovery.tcp.internal.TcpDiscoveryNode>)
> to order basing on per node attribute value
> # Node comparison should be stable and consistent. E.g. if CLUSTER_REGION_IDs
> are equal then we should compare nodes' IDs. This way we have consistent
> order on all nodes in topology.
> # Also nextNode() has to group nodes on same host and in same subnet. This
> can be postponed and implemented after we have other points done.
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