I believe that the
compensation handlers for parallel scopes should be processed in any order, by
default. The implication of parallel forward processing is that there is
unlikely to be data sharing (i.e. the services involved are unaware of each
other); it is reasonable to assume the same on the way out. If there is
sharing/awareness, then it’s a case of caveat emptor: don’t disorder the
necessarily ordered, or control the disorder very carefully at an application
level.
The spec as it stands
seems to unambiguously mandate “reverse completion order”, as a previous post
from Muruga Chinnananchi pointed out.
I suggest that after
the existing text in 13.3 ending:
“If the compensation handler
for a scope is absent, the default compensation handler invokes the
compensation handlers for the immediately enclosed scopes in the reverse order
of the completion of those scopes.”
be inserted the
additional text:
“When scopes are
executed in parallel, the default compensation handler of their immediately
enclosing scope shall invoke the compensation handler of each completed
enclosed scope, in an implementation-defined
order”
Alastair