lfs: fix the stall and corruption issue when concurrently uploading blobs
We've avoided the issue up to this point by gating worker usage with an
experimental config. See 10e62d5efa73, and the thread linked there for some of
the initial diagnosis, but essentially some data was being read from the blob
before an error occurred and `keepalive` retried, but didn't rewind the file
pointer. So the leading data was lost from the blob on the server, and the
connection stalled, trying to send more data than available.
In trying to recreate this, I was unable to do so uploading from Windows to
CentOS 7. But it reproduced every time going from CentOS 7 to another CentOS 7
over https.
I found recent fixes in the FaceBook repo to address this[1][2]. The commit
message for the first is:
The KeepAlive HTTP implementation is bugged in it's retry logic, it supports
reading from a file pointer, but doesn't support rewinding of the seek cursor
when it performs a retry. So it can happen that an upload fails for whatever
reason and will then 'hang' on the retry event.
The sequence of events that get triggered are:
- Upload file A, goes OK. Keep-Alive caches connection.
- Upload file B, fails due to (for example) failing Keep-Alive, but LFS file
pointer has been consumed for the upload and fd has been closed.
- Retry for file B starts, sets the Content-Length properly to the expected
file size, but since file pointer has been consumed no data will be uploaded,
causing the server to wait for the uploaded data until either client or
server reaches a timeout, making it seem as our mercurial process hangs.
This is just a stop-gap measure to prevent this behavior from blocking Mercurial
(LFS has retry logic). A proper solutions need to be build on top of this
stop-gap measure: for upload from file pointers, we should support fseek() on
the interface. Since we expect to consume the whole file always anyways, this
should be safe. This way we can seek back to the beginning on a retry.
I ported those two patches, and it works. But I see that `url._sendfile()` does
a rewind on `httpsendfile` objects[3], so maybe it's better to keep this all in
one place and avoid a second seek. We may still want the first FaceBook patch
as extra protection for this problem in general. The other two uses of
`httpsendfile` are in the wire protocol to upload bundles, and to upload
largefiles. Neither of these appear to use a worker, and I'm not sure why
workers seem to trigger this, or if this could have happened without a worker.
Since `httpsendfile` already has a `close()` method, that is dropped. That
class also explicitly says there's no `__len__` attribute, so that is removed
too. The override for `read()` is necessary to avoid the progressbar usage per
file.
[1] https://github.com/facebookexperimental/eden/commit/c350d6536d90c044c837abdd3675185644481469
[2] https://github.com/facebookexperimental/eden/commit/77f0d3fd0415e81b63e317e457af9c55c46103ee
[3] https://www.mercurial-scm.org/repo/hg/file/5.2.2/mercurial/url.py#l176
Differential Revision: https://phab.mercurial-scm.org/D7962
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ hg qinit
$ echo x > x
$ hg ci -Ama
adding x
$ hg qnew a.patch
$ echo a > a
$ hg add a
$ hg qrefresh
$ hg qnew b.patch
$ echo b > b
$ hg add b
$ hg qrefresh
$ hg qnew c.patch
$ echo c > c
$ hg add c
$ hg qrefresh
$ hg qpop -a
popping c.patch
popping b.patch
popping a.patch
patch queue now empty
should fail
$ hg qguard does-not-exist.patch +bleh
abort: no patch named does-not-exist.patch
[255]
should fail
$ hg qguard +fail
abort: no patches applied
[255]
$ hg qpush
applying a.patch
now at: a.patch
should guard a.patch
$ hg qguard +a
should print +a
$ hg qguard
a.patch: +a
$ hg qpop
popping a.patch
patch queue now empty
should fail
$ hg qpush a.patch
cannot push 'a.patch' - guarded by '+a'
[1]
$ hg qguard a.patch
a.patch: +a
should push b.patch
$ hg qpush
applying b.patch
now at: b.patch
$ hg qpop
popping b.patch
patch queue now empty
test selection of an empty guard
$ hg qselect ""
abort: guard cannot be an empty string
[255]
$ hg qselect a
number of unguarded, unapplied patches has changed from 2 to 3
should push a.patch
$ hg qpush
applying a.patch
now at: a.patch
$ hg qguard -- c.patch -a
should print -a
$ hg qguard c.patch
c.patch: -a
should skip c.patch
$ hg qpush -a
applying b.patch
skipping c.patch - guarded by '-a'
now at: b.patch
$ hg qnext
all patches applied
[1]
should display b.patch
$ hg qtop
b.patch
$ hg qguard -n c.patch
should push c.patch
$ hg qpush -a
applying c.patch
now at: c.patch
$ hg qpop -a
popping c.patch
popping b.patch
popping a.patch
patch queue now empty
$ hg qselect -n
guards deactivated
number of unguarded, unapplied patches has changed from 3 to 2
should push all
$ hg qpush -a
applying b.patch
applying c.patch
now at: c.patch
$ hg qpop -a
popping c.patch
popping b.patch
patch queue now empty
$ hg qguard a.patch +1
$ hg qguard b.patch +2
$ hg qselect 1
number of unguarded, unapplied patches has changed from 1 to 2
should push a.patch, not b.patch
$ hg qpush
applying a.patch
now at: a.patch
$ hg qpush
applying c.patch
now at: c.patch
$ hg qpop -a
popping c.patch
popping a.patch
patch queue now empty
$ hg qselect 2
should push b.patch
$ hg qpush
applying b.patch
now at: b.patch
$ hg qpush -a
applying c.patch
now at: c.patch
$ hg qprev
b.patch
Used to be an issue with holes in the patch sequence
So, put one hole on the base and ask for topmost patch.
$ hg qtop
c.patch
$ hg qpop -a
popping c.patch
popping b.patch
patch queue now empty
$ hg qselect 1 2
number of unguarded, unapplied patches has changed from 2 to 3
should push a.patch, b.patch
$ hg qpush
applying a.patch
now at: a.patch
$ hg qpush
applying b.patch
now at: b.patch
$ hg qpop -a
popping b.patch
popping a.patch
patch queue now empty
$ hg qguard -- a.patch +1 +2 -3
$ hg qselect 1 2 3
number of unguarded, unapplied patches has changed from 3 to 2
list patches and guards
$ hg qguard -l
a.patch: +1 +2 -3
b.patch: +2
c.patch: unguarded
have at least one patch applied to test coloring
$ hg qpush
applying b.patch
now at: b.patch
list patches and guards with color
$ hg --config extensions.color= qguard --config color.mode=ansi \
> -l --color=always
\x1b[0;30;1ma.patch\x1b[0m: \x1b[0;33m+1\x1b[0m \x1b[0;33m+2\x1b[0m \x1b[0;31m-3\x1b[0m (esc)
\x1b[0;34;1;4mb.patch\x1b[0m: \x1b[0;33m+2\x1b[0m (esc)
\x1b[0;30;1mc.patch\x1b[0m: \x1b[0;32munguarded\x1b[0m (esc)
should pop b.patch
$ hg qpop
popping b.patch
patch queue now empty
list series
$ hg qseries -v
0 G a.patch
1 U b.patch
2 U c.patch
list guards
$ hg qselect
1
2
3
should push b.patch
$ hg qpush
applying b.patch
now at: b.patch
$ hg qpush -a
applying c.patch
now at: c.patch
$ hg qselect -n --reapply -v
guards deactivated
popping guarded patches
popping c.patch
popping b.patch
patch queue now empty
reapplying unguarded patches
skipping a.patch - guarded by '+1' '+2'
skipping b.patch - guarded by '+2'
skipping a.patch - guarded by '+1' '+2'
skipping b.patch - guarded by '+2'
applying c.patch
patching file c
adding c
committing files:
c
committing manifest
committing changelog
now at: c.patch
guards in series file: +1 +2 -3
$ hg qselect -s
+1
+2
-3
should show c.patch
$ hg qapplied
c.patch
$ hg qrename a.patch new.patch
should show :
new.patch: +1 +2 -3
b.patch: +2
c.patch: unguarded
$ hg qguard -l
new.patch: +1 +2 -3
b.patch: +2
c.patch: unguarded
$ hg qnew d.patch
$ hg qpop
popping d.patch
now at: c.patch
should show new.patch and b.patch as Guarded, c.patch as Applied
and d.patch as Unapplied
$ hg qseries -v
0 G new.patch
1 G b.patch
2 A c.patch
3 U d.patch
qseries again, but with color
$ hg --config extensions.color= --config color.mode=ansi qseries -v --color=always
0 G \x1b[0;30;1mnew.patch\x1b[0m (esc)
1 G \x1b[0;30;1mb.patch\x1b[0m (esc)
2 A \x1b[0;34;1;4mc.patch\x1b[0m (esc)
3 U \x1b[0;30;1md.patch\x1b[0m (esc)
$ hg qguard d.patch +2
new.patch, b.patch: Guarded. c.patch: Applied. d.patch: Guarded.
$ hg qseries -v
0 G new.patch
1 G b.patch
2 A c.patch
3 G d.patch
$ qappunappv()
> {
> for command in qapplied "qapplied -v" qunapplied "qunapplied -v"; do
> echo % hg $command
> hg $command
> done
> }
$ hg qpop -a
popping c.patch
patch queue now empty
$ hg qguard -l
new.patch: +1 +2 -3
b.patch: +2
c.patch: unguarded
d.patch: +2
$ qappunappv
% hg qapplied
% hg qapplied -v
% hg qunapplied
c.patch
% hg qunapplied -v
0 G new.patch
1 G b.patch
2 U c.patch
3 G d.patch
$ hg qselect 1
number of unguarded, unapplied patches has changed from 1 to 2
$ qappunappv
% hg qapplied
% hg qapplied -v
% hg qunapplied
new.patch
c.patch
% hg qunapplied -v
0 U new.patch
1 G b.patch
2 U c.patch
3 G d.patch
$ hg qpush -a
applying new.patch
skipping b.patch - guarded by '+2'
applying c.patch
skipping d.patch - guarded by '+2'
now at: c.patch
$ qappunappv
% hg qapplied
new.patch
c.patch
% hg qapplied -v
0 A new.patch
1 G b.patch
2 A c.patch
% hg qunapplied
% hg qunapplied -v
3 G d.patch
$ hg qselect 2
number of unguarded, unapplied patches has changed from 0 to 1
$ qappunappv
% hg qapplied
new.patch
c.patch
% hg qapplied -v
0 A new.patch
1 U b.patch
2 A c.patch
% hg qunapplied
d.patch
% hg qunapplied -v
3 U d.patch
$ for patch in `hg qseries`; do
> echo % hg qapplied $patch
> hg qapplied $patch
> echo % hg qunapplied $patch
> hg qunapplied $patch
> done
% hg qapplied new.patch
new.patch
% hg qunapplied new.patch
b.patch
d.patch
% hg qapplied b.patch
new.patch
% hg qunapplied b.patch
d.patch
% hg qapplied c.patch
new.patch
c.patch
% hg qunapplied c.patch
d.patch
% hg qapplied d.patch
new.patch
c.patch
% hg qunapplied d.patch
hg qseries -m: only b.patch should be shown
the guards file was not ignored in the past
$ hg qdelete -k b.patch
$ hg qseries -m
b.patch
hg qseries -m with color
$ hg --config extensions.color= --config color.mode=ansi qseries -m --color=always
\x1b[0;31;1mb.patch\x1b[0m (esc)
excercise corner cases in "qselect --reapply"
$ hg qpop -a
popping c.patch
popping new.patch
patch queue now empty
$ hg qguard -- new.patch -not-new
$ hg qguard -- c.patch -not-c
$ hg qguard -- d.patch -not-d
$ hg qpush -a
applying new.patch
applying c.patch
applying d.patch
patch d.patch is empty
now at: d.patch
$ hg qguard -l
new.patch: -not-new
c.patch: -not-c
d.patch: -not-d
$ hg qselect --reapply not-d
popping guarded patches
popping d.patch
now at: c.patch
reapplying unguarded patches
cannot push 'd.patch' - guarded by '-not-d'
$ hg qser -v
0 A new.patch
1 A c.patch
2 G d.patch
$ hg qselect --reapply -n
guards deactivated
$ hg qpush
applying d.patch
patch d.patch is empty
now at: d.patch
$ hg qser -v
0 A new.patch
1 A c.patch
2 A d.patch
$ hg qselect --reapply not-c
popping guarded patches
popping d.patch
popping c.patch
now at: new.patch
reapplying unguarded patches
applying d.patch
patch d.patch is empty
now at: d.patch
$ hg qser -v
0 A new.patch
1 G c.patch
2 A d.patch
$ hg qselect --reapply not-new
popping guarded patches
popping d.patch
popping new.patch
patch queue now empty
reapplying unguarded patches
applying c.patch
applying d.patch
patch d.patch is empty
now at: d.patch
$ hg qser -v
0 G new.patch
1 A c.patch
2 A d.patch
test that qselect shows "number of guarded, applied patches" correctly
$ hg qimport -q -e b.patch
adding b.patch to series file
$ hg qguard -- b.patch -not-b
$ hg qpop -a -q
patch queue now empty
$ hg qunapplied -v
0 G new.patch
1 U c.patch
2 U d.patch
3 U b.patch
$ hg qselect not-new not-c
number of unguarded, unapplied patches has changed from 3 to 2
$ hg qpush -q -a
patch d.patch is empty
now at: b.patch
$ hg qapplied -v
0 G new.patch
1 G c.patch
2 A d.patch
3 A b.patch
$ hg qselect --none
guards deactivated
$ hg qselect not-new not-c not-d
number of guarded, applied patches has changed from 0 to 1
test that "qselect --reapply" reapplies patches successfully when the
already applied patch becomes unguarded and it follows the already
guarded (= not yet applied) one.
$ hg qpop -q -a
patch queue now empty
$ hg qselect not-new not-c
number of unguarded, unapplied patches has changed from 1 to 2
$ hg qpush -q -a
patch d.patch is empty
now at: b.patch
$ hg qapplied -v
0 G new.patch
1 G c.patch
2 A d.patch
3 A b.patch
$ hg qselect -q --reapply not-c not-b
now at: d.patch
cannot push 'b.patch' - guarded by '-not-b'
$ hg qseries -v
0 U new.patch
1 G c.patch
2 A d.patch
3 G b.patch
test that "qselect --reapply" checks applied patches correctly when no
applied patches becomes guarded but some of unapplied ones become
unguarded.
$ hg qpop -q -a
patch queue now empty
$ hg qselect not-new not-c not-d
number of unguarded, unapplied patches has changed from 2 to 1
$ hg qpush -q -a
now at: b.patch
$ hg qapplied -v
0 G new.patch
1 G c.patch
2 G d.patch
3 A b.patch
$ hg qselect -q --reapply not-new not-c
$ hg qseries -v
0 G new.patch
1 G c.patch
2 U d.patch
3 A b.patch