view CONTRIBUTORS @ 32024:ad41739c6b2b

bundle2: ignore errors seeking a bundle after an exception (issue4784)

Many have seen a "stream ended unexpectedly" error. This message is
raised from changegroup.readexactly() when a read(n) operation fails
to return exactly N bytes.

I believe most occurrences of this error in the wild stem from
the code changed in this patch. Before, if bundle2's part applicator
raised an Exception when processing/applying parts, the exception
handler would attempt to iterate the remaining parts. If I/O
during this iteration failed, it would likely raise the
"stream ended unexpectedly" exception.

The problem with this approach is that if we already encountered
an I/O error iterating the bundle2 data during application, then
any further I/O would almost certainly fail. If the original stream
were closed, changegroup.readexactly() would obtain an empty
string, triggering "stream ended unexpectedly" with "got 0." This is
the error message that users would see. What's worse is that the
original I/O related exception would be lost since a new exception
would be raised. This made debugging the actual I/O failure
effectively impossible.

This patch changes the exception handler for bundle2 application to
ignore errors when seeking the underlying stream. When the underlying
error is I/O related, the seek should fail fast and the original
exception will be re-raised. The output changes in
test-http-bad-server.t demonstrate this.

When the underlying error is not I/O related and the stream can be
seeked, the old behavior is preserved.

[This file is here for historical purposes, all recent contributors
should appear in the changelog directly]

Andrea Arcangeli <andrea at suse.de>
Thomas Arendsen Hein <thomas at intevation.de>
Goffredo Baroncelli <kreijack at libero.it>
Muli Ben-Yehuda <mulix at mulix.org>
Mikael Berthe <mikael at lilotux.net>
Benoit Boissinot <bboissin at gmail.com>
Brendan Cully <brendan at kublai.com>
Vincent Danjean <vdanjean.ml at free.fr>
Jake Edge <jake at edge2.net>
Michael Fetterman <michael.fetterman at intel.com>
Edouard Gomez <ed.gomez at free.fr>
Eric Hopper <hopper at omnifarious.org>
Alecs King <alecsk at gmail.com>
Volker Kleinfeld <Volker.Kleinfeld at gmx.de>
Vadim Lebedev <vadim at mbdsys.com>
Christopher Li <hg at chrisli.org>
Chris Mason <mason at suse.com>
Colin McMillen <mcmillen at cs.cmu.edu>
Wojciech Milkowski <wmilkowski at interia.pl>
Chad Netzer <chad.netzer at gmail.com>
Bryan O'Sullivan <bos at serpentine.com>
Vicent Seguí Pascual <vseguip at gmail.com>
Sean Perry <shaleh at speakeasy.net>
Nguyen Anh Quynh <aquynh at gmail.com>
Ollivier Robert <roberto at keltia.freenix.fr>
Alexander Schremmer <alex at alexanderweb.de>
Arun Sharma <arun at sharma-home.net>
Josef "Jeff" Sipek <jeffpc at optonline.net>
Kevin Smith <yarcs at qualitycode.com>
TK Soh <teekaysoh at yahoo.com>
Radoslaw Szkodzinski <astralstorm at gorzow.mm.pl>
Samuel Tardieu <sam at rfc1149.net>
K Thananchayan <thananck at yahoo.com>
Andrew Thompson <andrewkt at aktzero.com>
Michael S. Tsirkin <mst at mellanox.co.il>
Rafael Villar Burke <pachi at mmn-arquitectos.com>
Tristan Wibberley <tristan at wibberley.org>
Mark Williamson <mark.williamson at cl.cam.ac.uk>