[jboss-jira] [JBoss JIRA] Commented: (JGRP-129) Logical addresses

[Bela Ban (JIRA)]

    [ http://jira.jboss.com/jira/browse/JGRP-129?page=comments#action_12370883 ] 
            
Bela Ban commented on JGRP-129:
-------------------------------

I'm not sure I want to introduce logical addresses. This is regarding
JGRP-129 (logical addresses)  and JGRP-130 (problems with reincarnation).

JGRP-130 is about a member that leaves and rejoins *under the same IP address and port (using bind/start_port)* before failure detection kicks it out. I implemented a fix for this, which won't allow a member into the group that's already in the group. In the above case, with A and B, B would have to wait until the cluster is {A} before it can rejoin.

JGRP-129 is about providing a logical address (possibly host + system time in ms (plus 1 for same system times) for a member, which can be mapped to a physical host/port combo. It would add 4 bytes/address, and I don't see the benefits of this.

The original motivation was that when a member gets shunned, it rejoins under a new identity. Sacha didn't like this and therefore added 'logical addresses' in JBoss, which creates a logical address for a member. So when that member is shunned and rejoins under a *new* JGroups address, it would still keep the *old* JBoss logical address.

I tend to leave it this way, as I don't want to add something which
- adds clutter (Host:26634425614 looks less readable than Host:4536)
- adds 4 bytes / IpAddress
- has some additional lookup in the transport to find the real physical address to which the logical address maps
- needs some ARP-like traffic for establishing local tables which map logical to physical addresses

What do people think ?

> Logical addresses
> -----------------
>
>                 Key: JGRP-129
>                 URL: http://jira.jboss.com/jira/browse/JGRP-129
>             Project: JGroups
>          Issue Type: Feature Request
>    Affects Versions: 2.2.9
>            Reporter: Bela Ban
>         Assigned To: Bela Ban
>             Fix For: 2.6
>
>
> The address chosen by each node is essentially the IP address and port of the receiver socket. However, for the following reasons, this is not good enough:
> - The node is shunned (excluded) and re-joins after leaving. We'd like to have the same logical address, although the physical address changed. This is already done in JBoss code, should be available in JGroups proper
> - NIC failover: a NIC goes down, we want to continue sending/receiving on a different NIC
> - The sender sends on all available NICs (send_on_all_interfaces="true"). This means that -if we take the receiver's datagram packet's address to be the identity of the sender - we get N different identities; 1 for each interface the message is sent on
> - Network Address Translation: the sender's address might get changed by the NAT
> DESIGN: 
> - A logical address is picked, either by JGroups, or set by a user on channel creation. The lifetime of this address is the lifetime of the process in which the channel is created, or until channel.close() or disconnect() is called.
> - Each member as a small cache, in which it associates the logical addresses for messages received with the sender's address. When a message is to be sent to a logical address (unicast message), the corresponding physical address is looked up from the cache. Note that there maybe multiple physical addresses if the same message was sent on different interfaces (send_on_all_interfaces="true").
> - The logical addresses must be picked such that they cannot be reused after disconnect()/close().

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