Re: [PATCH 2/4] transport-helper: check if remote helper is alive

On Mon, Apr 1, 2013 at 11:01 PM, Jeff King [off-list ref] wrote:

On Mon, Apr 01, 2013 at 10:51:20PM -0600, Felipe Contreras wrote:

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So in fetch_with_import, we have a remote-helper, and we have a
bidirectional pipe to it. We then call get_importer, which starts
fast-import, whose stdin is connected to the stdout of the remote
helper. We tell the remote-helper to run the import, then we wait for
fast-import to finish (and complain if it fails).

Then what? We seem to do some more work, which I think is what causes
the errors you see; but should we instead be reaping the helper at this
point unconditionally? Its stdout has presumably been flushed out to
fast-import; is there anything else for us to get from it besides its
exit code?

The problem is not with import, since fast-import would generally wait
properly for a 'done' status, the problem is with export.

Your patch modified fetch_with_import. Are you saying that it isn't
necessary to do so?

It's not, I added it for symmetry. But that's the case *if* the
remote-helper is properly using the "done" feature.

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Also, the design is such that the remote-helper stays alive, even
after fast-export has finished.

So if we expect to be able to communicate with the remote-helper after
fast-export has exited, is it a protocol failure that the helper does
not say "yes, I finished the export" or similar? If so, can we fix that?

I am not too familiar with this protocol, but it looks like we read from
helper->out right after closing the exporter, to get the ref statuses.
Shouldn't we be detecting the error if the helper hangs up there?

I guess that should be possible, I'll give that a try.

Cheers.

-- 
Felipe Contreras