[Swift-devel] Re: more ftp errors running terminable->tg uc

[Ben Clifford]

I have dug some more into this.

The cog gridftp provider enables data channel reuse when talking to 
gridftp servers that report exactly version 2.3.

Some of the sites that I am testing against report that version. Some 
report version 2.5.

The sites which are version 2.3 fail to run test workflow '130-fmri' in 
the tests/language-behaviour directory. The sites which are not 2.3 do not 
exhibit this problem.

This happens submitting from both tg-login1.uc.teragrid.org and from 
terminable.ci.uchicago.edu

On terminable:

If I change the cog gridftp provider to enable gridftp data channel reuse 
for version 2.5 too, then the 2.5 sites also break.

If I disable data channel reuse entirely (which appears to need a source 
code change) then all site tests work ok.

There are two separate issues here:

This needs fixing in general, presumably in cog. At the moment, I'm not 
particularly inclined to spend large amounts of time learning how the cog 
ftp provider works when potentially mihael could look at it. However, its 
unclear how much time mihael has to work on this, given his other projects 
and I have no particular belief that it will be fixed any time soon.

In a Swift-specific context, I'm happy for data-channel reuse to be turned 
off for now (eg until someone figures out what is up at the cog level) - 
its already not used for any recent gridftp server (i.e. v2.5) such as 
tg-gridftp.uc.teragrid.org.

No one has reported this as a problem in the wild (yet). I suspect test 
130-fmri is especially good at exhibiting this problem.

I think therefore that this should not be a release-stopped for 0.4; but 
that should anyone actually come across it in the wild we should rapidly 
put out a 0.4.1 or a 0.5 with data channel caching disabled.

I would appreciate commentary on:

   i) the above release proposal

  ii) the likelihood that Mihael will have time to look at this and when 
      that would happen (which is essentially the question - do I have to 
      go learn the guts of the gt2 cog provider?)

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