[jboss-dev-forums] [JBoss Transactions Development] - Re: Remote txinflow: XID changes
David Lloyd [http://community.jboss.org/people/dmlloyd] created the discussion
"Re: Remote txinflow: XID changes"
To view the discussion, visit: http://community.jboss.org/message/630611#630611
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Tom Jenkinson wrote:
Only the root TM would be in the gtrid, we can't edit that as the transaction flows.
But for recovery we only need the root TM right? That would eliminate the risk of
a subordinate TM recovering a branch of a transaction because it would recognize that it
wasn't the root?
Tom Jenkinson wrote:
Again, each RM will need to put its own name in the XID so again we can't cat this
into the gtrid.
Okay, so the gtid gets the root TM's name and the bqual gets the
RM name (assuming such things have names)?
Tom Jenkinson wrote:
Ah, understood. I was thinking the first few bits were binary, hence 100 could have been
either read as 1 (for 1 trailing nybble) or 100 (for 4). Now I get you, the prefix is the
number of nybbles, like in roman numerals.
If it is 0 terminated as you show above though, it looks like 1111 10xx xxxx xxxx xxxx
xxxx should really be 1111 10xx xxxx xxxx xxxx xxxx xxxx (five trailing nybbles AFTER the
nybble where the counter prefix finishes? Or should it be read as the number of
"total number of nybbles (less one) that the number is read from". E.g in your
last case the number has been encoded in 5 plus 1 nybbles.
Well, I meant 5 nybbles
holding data however after reviewing I guess that's not really correct. It would be
more correct to say "the number of nybbles in the total encoded number = the leading
number of 1s plus 1". With 0000 being a special case.
Tom Jenkinson wrote:
Anyway, for the purposes of the discussion I get what you are proposing, I guess the
question would be when it comes to recovery, when the node recovers how does it know which
XIDs it should be looking for? With my proposal where the node is configured with a node
ID via the CoreEnvironmentBean it can look in the XID for a match, in your scenario how
would it know?
Assuming that transactions should only be recovered by the root node
which originated it, we would just use gtid to identify the "ownership" of the
transaction. Otherwise, all the known unrecovered XIDs from the node itself plus its
subordinates should be propagated back upon recovery request. I'd also need some kind
of loop detection at the protocol level though.
We could potentially optimize this process by using our knowledge of the XID format to
filter the XID list by owner name before sending it back to the requestor.
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