[jboss-dev-forums] [JBoss Transactions Development] - Re: Remote txinflow: XID changes

[Tom Jenkinson]

Tom Jenkinson [http://community.jboss.org/people/tomjenkinson] created the discussion

"Re: Remote txinflow: XID changes"

To view the discussion, visit: http://community.jboss.org/message/633157#633157

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Hi David,

I was wondering about something like that (i.e. reducing the "domain" of the character space). The main reason I backed out is a point I raised earlier:

"node names must be unique per instance"

This means that the host name (or a derivative thereof) is not unique enough. Lets say you have two instances on the same machine, lets say we got it into 42 bits (although to be fair we could allocate 6 bytes per name if that helped - 28 for the Uid, 6 per node name leaving 24 bytes for the EISname). Anyway lets say the name was "foo".

If you start up two servers with the node name "foo" you can't flow transactions between them as the node identifier is the same, fairly clear if "foo" is on a different server, but potentially it could be on the same server, i.e. the user could start up more than one instance on host "foo". Hence you would need to configure node identifiers to be "foo1" and "foo2" anyway, leading to an integer and therefore leading to needing to configure this integer somewhere (presumably the same place where the integer I was talking about would need to be - a central configuration repository). You see the node identifier defines who "owns" transaction logs (this is an exisiting requirement - not new for this release). If you are thinking about some kind of "launch counter" where we could launch servers with a locally incremented suffix (as I would be  :)  ) then that isn't really good enough as the user would want to deterministically know the server they are launching to know which transactions are going to be restored.

The other issue is that hostnames may be none roman alphabet leading to quite a few more options, take the servers listed on:  http://en.wikipedia.org/wiki/List_of_Internet_top-level_domains#Test_TLDs http://en.wikipedia.org/wiki/List_of_Internet_top-level_domains#Test_TLDs or the ones from  http://www.w3.org/2003/Talks/0425-duerst-idniri/slide12-0.html http://www.w3.org/2003/Talks/0425-duerst-idniri/slide12-0.html such as  http://räksmörgås.josefsson.org/ http://räksmörgås.josefsson.org/

Also, arguably by asking the user to "choose a unique 8-character name" we might as well ask them to choose a unique int instead?

Just to clarify, this requirement for unique node names is an exisiting requirement of JBoss Transactions, but in the JTA none-shared object store scenario it has been sufficient to give the same node identifier.

Tom
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