Since the annex-tracking-branch is pushed first, git-annex has already
updated the export database when the DATA-PRESENT arrives. Which means
that just using checkPresent is enough to verify that there is some file
on the special remote in the export location for the key.
So, the simplest possible implementation of this happened to work!
(I also tested it with chunked specialremotes, which also works, as long
as the chunk size used is the same as the configured chunk size. In that
case, the lack of a chunk log is not a problem. Doubtful this will ever
make sense to use with a chunked special remote though, that gets pretty
deep into re-implementing git-annex.)
Updated the client side upload tip with a missing step, and reorged for clarity.
Apparently the protoerrhandler parameter never runs. Also the const
typo prevented the type checker from complaining that relayPUTRecord was
being called with 1 less parameter than needed.
So move the relayPUTRecord out of it.
Only indicate that we're done with the bytestring once it all gets written.
Otherwise, the end of it may get garbage collected before we can process
it, leading to a hang.
This seems to have been introduced in commit
cdc4bd7443. Which oddly was trying to fix a
very similar problem, but specific to a cluster node. In that commit,
things got out of order, with it signaling it was done with the bytestring
before it has written all of it to the file.
My test case for this bug is a directory special remote
with a file being sent to it via a proxy accessed via ssh or http.
The file was 10 mb, and it hung on the last few kb of it not being
received.
I've also tested this fix in the case of proxying to a cluster node
directory special remote over http, which was the case
cdc4bd7443 was dealing with.
I wonder where else this could be documented? It's kind of a niche
feature, since it needs at least a partial custom implementation of the p2p
protocol or the p2phttp protocol. But it can save a lot of bandwidth and
avoid the proxy needing disk space to buffer files uploaded to a special
remote.
There is a TODO left in the code for exporttree special remotes. If
possible, it should check if one of the export locations contains the
content of the key.
But not yet when proxying to special remotes.
When proxying for a cluster, the client can store the object on any node
or nodes of the cluster, and send DATA-PRESENT. That gets proxied to each
node, and if any of them agree that they have the data, the proxy will
respond with SUCCESS or SUCCESS-PLUS.
I think it's ok to not check for the proxied remotes supporting protocol
version 4. When there are multiple remotes in a cluster, it behaves as
described above, and if they all respond with ERROR, the result will be
FAILURE. And when not proxying for a cluster, the proxy negotiates the
p2p protocol to be the same version or lower than the proxied remote,
which will prevent sending DATA-PRESENT when it's too old.
Changed the protocol docs because servant parses "true" and "false" for
booleans in query parameters, not "1" and "0".
clientPut with datapresent=True is not used by git-annex, and I don't
anticipate it being used in git-annex, except for testing.
I've tested this by making clientPut be called with datapresent=True and
git-annex copy to a remote succeeds once the object file is first
manually copied to the remote. That would be a good test for the test
suite, but running the http client means exposing it to at least
localhost, and would fail if a real http client was already running on
that port.
