#1525: SFTP: handle download failures correctly
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Reporter: davidsarah | Owner:
Type: defect | davidsarah
Priority: major | Status: new
Component: code-frontend | Milestone: soon
Keywords: sftp hang error streaming | Version: 1.9.0a1
performance test-needed | Launchpad Bug:
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Brian noticed that a Deferred was being dropped at
[source:src/allmydata/frontends/sftpd.py at 5179#L676]. (Although this code
changed when MDMF landed [5179], the immutable path of the
[source:src/allmydata/frontends/sftpd.py at 5127#L675 previous code] also
dropped a Deferred, at line 680.)
It is incorrect to drop the Deferred, because that will cause SFTP read
requests to hang if downloading the previous file contents fails. However
fixing it while still allowing streaming reads is a bit tricky. The
intention is that we download the file in parallel with accepting SFTP
requests, and block each read request until the relevant part of the file
is available (and prior writes have completed). If the download fails,
then any SFTP read requests past the prefix that was read correctly should
also fail. Also, if the file was written and not truncated, the SFTP close
request should fail, at least in the case when the new contents depend on
the part of the old contents that we weren't able to download.
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Ticket URL: <http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1525>
tahoe-lafs <http://tahoe-lafs.org>
secure decentralized storage