Is DDFS HTTP POST to Tag Atomic?

[Giles Brown]

I've been reading the docs for the DDFS Web API, http://disco.readthedocs.org/en/latest/howto/ddfs.html#web-api.

There are a number of references to tag operations being done on the master to ensure atomicity and consistency.

I was wondering if any of my fellow Disco developers/users (there is overlap of course)  had enough knowledge to say if the POST was atomic.

Specifically if I POST URLs to a tag:

    curl -x POST -d '[["http://foo"]]' http://disco:8989/ddfs/tag/MYTAG

And from somewhere else a simultaneous post of '[["http://bar"]]' happens, then is the ordering of the URLs in the tag is fixed.  In other words,

whichever URL gets in first, stays first in the list.  Does anybody know this to be correct or incorrect?  I think it's probably true, but I'm looking for certainty (or very close to it).

Giles

[Giles Brown]

Oh I really thought somebody would want to answer this question! :)