New issue: standard tid request for XA

[Mark Little <mlittle@redhat.com>]

A common interaction pattern when using WS-AtomicTransaction is bridging between XA domains. XA has a well defined format for TIDs and it would be nice (aka helpful for users and developers) if we also had a standard format for WS-AT TIDs that matched, when running in these kinds of environment, i.e., not mandated for all uses of WS-AT, but an optional supported capability when the coordinator and participants agree.

Here is one simple suggestion (from one of our developers): a transaction id scheme ("trid"), followed by a path that contains only the formatId and by a query ("?") that contains the globalTransactionId part of the Xid. 

    trid:<formatId>?<globalTransactionId>

The <formatId> part is either -1 (to represent a null transaction id) or the decimal representation of a non-negative 32-bit integer. 

The query part (?<globalTransactionId>) shall be present if and only if the formatId is not -1. The <globalTransactionId> is a percent-encoded representation (according to the percent-encoding conventions in RFC 3986) of the global transaction id part of the Xid. 

Examples:

    "trid:-1" (null trid)

   

    "trid:6789?http://Fabrikam123.com/SS/1234" (formatId=6789, globalTransactionId=" http://Fabrikam123.com/SS/1234")

    "trid:6789?%00%01%02%03%04%05%06%07%08%09%0A%0B%0C%0D%0E%0F%F0%FF" (formatId=6789, globalTransactionId=[00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F F0 FF]) 

The use of a query ("?") for the globalTransactionId part eliminates the need for percent-encoding any occurrences of the chars "/" or "?" in the global transaction id. This is good for global transaction ids that are URIs. (This is the case in the second example above). 

Note that there is no branch qualifier in a trid URI, as branch qualifiers do not need to be propagated across TMs/appservers. This is the main reason we would prefer an URI scheme like "trid" (over "xid", which suggests the presence of a branch qualifier). 

This proposal is better for textual global ids than for binary ones. We could have an alternate scheme that would make binary global ids shorter, e.g.:

 

    "hextrid:6789?000102030405060708090A0B0C0D0E0FF0FF" 

Or we could still use the same "trid" scheme and have a longer path instead of a query:

    "trid:6789:000102030405060708090A0B0C0D0E0FF0FF"

The occurrence of a ":" instead of a "?" would indicate that the global id is hex-encoded within the path. 

Mark.

----

Mark Little

mlittle@redhat.com

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