| Message ID | 20181220164150.GB25639@hank.intra.tgummerer.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | t5570: drop racy test | expand |
On Thu, Dec 20, 2018 at 04:41:50PM +0000, Thomas Gummerer wrote: > > That doesn't really fix it, but just broadens the race window. I dunno. > > Maybe that is enough in practice. We could do something like: > > > > repeat_with_timeout () { > > local i=0 > > while test $i -lt 10 > > do > > "$@" && return 0 > > sleep 1 > > done > > # no success even after 10 seconds > > return 1 > > } > > > > repeat_with_timeout grep -i extended.attribute daemon.log > > > > to make the pattern a bit more obvious (and make it easy to extend the > > window arbitrarily; surely 10s is enough?). > > I gave this a try, with below patch to lib-git-daemon.sh that you > proposed in the previous thread about this racyness. That shows > another problem though, namely when truncating 'daemon.log' before > running 'git ls-remote' in this test, we're not sure all 'git deamon' > has flushed everything from previous invocations. That may be an even > rarer problem in practice, but still something to keep in mind. Right, that makes sense. Making this race-proof really does require a separate log stream for each test. I guess we'd need to be able to send git-daemon a signal to re-open the log (which actually is not as unreasonable as it may seem; lots of daemons have this for log rotation). I think getting rid of the "cat" would also help a lot here. Unfortunately I think we use it not just for its "tee" effect, but also to avoid startup races by checking the "Ready to rumble" line. So again, we'd need some cooperation from git-daemon to tell us out-of-band that it has completed its startup (e.g., by touching another file). > Dscho also mentioned on #git-devel a while ago that he may have a look > at actually making this test race-proof, but I guess he's been busy > with the 2.20 release. I'm also not sure it's worth spending a lot of > time trying to fix this test, but I'd definitely be happy if someone > proposes a different solution. Yeah. I'm sure it's fixable with enough effort, but I just think there are more interesting and important things to work on. > --- >8 --- > Subject: [PATCH] t5570: drop racy test So yeah, I'm still fine with this. But... > --- > t/t5570-git-daemon.sh | 13 ------------- > 1 file changed, 13 deletions(-) This is the only user of daemon.log, so we could drop those bits from lib-git-daemon.sh, too. That would also prevent people from adding new tests, thinking that this was somehow not horribly racy). I.e., reverting 314a73d658 (t/lib-git-daemon: record daemon log, 2018-01-25). -Peff
Hi Thomas & Peff, On Thu, 20 Dec 2018, Jeff King wrote: > On Thu, Dec 20, 2018 at 04:41:50PM +0000, Thomas Gummerer wrote: > > > > That doesn't really fix it, but just broadens the race window. I dunno. > > > Maybe that is enough in practice. We could do something like: > > > > > > repeat_with_timeout () { > > > local i=0 > > > while test $i -lt 10 > > > do > > > "$@" && return 0 > > > sleep 1 > > > done > > > # no success even after 10 seconds > > > return 1 > > > } > > > > > > repeat_with_timeout grep -i extended.attribute daemon.log > > > > > > to make the pattern a bit more obvious (and make it easy to extend the > > > window arbitrarily; surely 10s is enough?). > > > > I gave this a try, with below patch to lib-git-daemon.sh that you > > proposed in the previous thread about this racyness. That shows > > another problem though, namely when truncating 'daemon.log' before > > running 'git ls-remote' in this test, we're not sure all 'git deamon' > > has flushed everything from previous invocations. That may be an even > > rarer problem in practice, but still something to keep in mind. > > Right, that makes sense. Making this race-proof really does require a > separate log stream for each test. I guess we'd need to be able to send > git-daemon a signal to re-open the log (which actually is not as > unreasonable as it may seem; lots of daemons have this for log > rotation). > > I think getting rid of the "cat" would also help a lot here. > Unfortunately I think we use it not just for its "tee" effect, but also > to avoid startup races by checking the "Ready to rumble" line. So again, > we'd need some cooperation from git-daemon to tell us out-of-band that > it has completed its startup (e.g., by touching another file). > > > Dscho also mentioned on #git-devel a while ago that he may have a look > > at actually making this test race-proof, but I guess he's been busy > > with the 2.20 release. And GitGitGadget. And working on the Azure Pipelines support. And mentoring two interns. This is what I still have in my internal ticket: Try to work around occasional t5570 failures in Git's test suite Seems that there is a race condition in https://github.com/git/git/blob/master/t/lib-git-daemon.sh#L48-L69 that could possibly be solved by writing to the daemon.log directly, and showing the output only via `tail -f` (and only when running in verbose mode, as it simply won't make sense otherwise). However, if the preferred route is to go ahead and just remove that test altogether, I'm fine with that, too. The only reason, in my mind, why we still have `git-daemon` is that it allows for easy standing up your own Git server, e.g. as an ad-hoc way to collaborate in a small ad-hoc team. If we ever get to the point where we can stand up a minimal HTTP/HTTPS server with an internal Git command (not requiring sysadmin privileges), from my point of view `git-daemon` can even go the way of the Kale Island (but for much better reasons [*1*]). > > I'm also not sure it's worth spending a lot of time trying to fix this > > test, but I'd definitely be happy if someone proposes a different > > solution. > > Yeah. I'm sure it's fixable with enough effort, but I just think there > are more interesting and important things to work on. > > > --- >8 --- > > Subject: [PATCH] t5570: drop racy test > > So yeah, I'm still fine with this. But... > > > --- > > t/t5570-git-daemon.sh | 13 ------------- > > 1 file changed, 13 deletions(-) > > This is the only user of daemon.log, so we could drop those bits from > lib-git-daemon.sh, too. That would also prevent people from adding new > tests, thinking that this was somehow not horribly racy). I.e., > reverting 314a73d658 (t/lib-git-daemon: record daemon log, 2018-01-25). Indeed, that would be good. The only reason to keep daemon.log that I can think of is to make debugging easier, but then, if it should become necessary, it is probably easier to freopen() stdout or stderr into a file in `git daemon`, anyway. Ciao, Dscho Footnote *1*: Kale Island, along with Rapita, Rehana, Kakatina and Zollies is prominently featured in a scientific article at http://iopscience.iop.org/article/10.1088/1748-9326/11/5/054011 that is on my "important papers I read in 2018" list.
On 12/21, Johannes Schindelin wrote: > Hi Thomas & Peff, > > On Thu, 20 Dec 2018, Jeff King wrote: > > > On Thu, Dec 20, 2018 at 04:41:50PM +0000, Thomas Gummerer wrote: > > > > > Dscho also mentioned on #git-devel a while ago that he may have a look > > > at actually making this test race-proof, but I guess he's been busy > > > with the 2.20 release. > > And GitGitGadget. And working on the Azure Pipelines support. And > mentoring two interns. > > This is what I still have in my internal ticket: > > Try to work around occasional t5570 failures in Git's test suite > > Seems that there is a race condition in > https://github.com/git/git/blob/master/t/lib-git-daemon.sh#L48-L69 > that could possibly be solved by writing to the daemon.log > directly, and showing the output only via `tail -f` (and only when > running in verbose mode, as it simply won't make sense otherwise). > > However, if the preferred route is to go ahead and just remove that test > altogether, I'm fine with that, too. Right, I was of course completely unaware of that internal ticket. If you still want to go that way there are certainly no objections from me. I just want to make sure not more users run into this racyness, and I guess you also may have more important/interesting things to work on. > The only reason, in my mind, why we still have `git-daemon` is that it > allows for easy standing up your own Git server, e.g. as an ad-hoc way to > collaborate in a small ad-hoc team. If we ever get to the point where we > can stand up a minimal HTTP/HTTPS server with an internal Git command (not > requiring sysadmin privileges), from my point of view `git-daemon` can > even go the way of the Kale Island (but for much better reasons [*1*]). > > > > I'm also not sure it's worth spending a lot of time trying to fix this > > > test, but I'd definitely be happy if someone proposes a different > > > solution. > > > > Yeah. I'm sure it's fixable with enough effort, but I just think there > > are more interesting and important things to work on. > > > > > --- >8 --- > > > Subject: [PATCH] t5570: drop racy test > > > > So yeah, I'm still fine with this. But... > > > > > --- > > > t/t5570-git-daemon.sh | 13 ------------- > > > 1 file changed, 13 deletions(-) > > > > This is the only user of daemon.log, so we could drop those bits from > > lib-git-daemon.sh, too. That would also prevent people from adding new > > tests, thinking that this was somehow not horribly racy). I.e., > > reverting 314a73d658 (t/lib-git-daemon: record daemon log, 2018-01-25). Right that makes sense. I sent that as patch 2/1, but I'm happy to squash those into one if that's preferred. > Indeed, that would be good. > > The only reason to keep daemon.log that I can think of is to make > debugging easier, but then, if it should become necessary, it is probably > easier to freopen() stdout or stderr into a file in `git daemon`, anyway. We do still print the output when tests are run in verbose mode, which should be just as good as having the log in a separate file in most cases I suspect. > Ciao, > Dscho > > Footnote *1*: Kale Island, along with Rapita, Rehana, Kakatina and Zollies > is prominently featured in a scientific article at > http://iopscience.iop.org/article/10.1088/1748-9326/11/5/054011 that is on > my "important papers I read in 2018" list.
diff --git a/t/lib-git-daemon.sh b/t/lib-git-daemon.sh index edbea2d986..3c7fea169b 100644 --- a/t/lib-git-daemon.sh +++ b/t/lib-git-daemon.sh @@ -62,6 +62,7 @@ start_git_daemon() { ( while read -r line <&7 do + sleep 1 printf "%s\n" "$line" printf >&4 "%s\n" "$line" done Dscho also mentioned on #git-devel a while ago that he may have a look at actually making this test race-proof, but I guess he's been busy with the 2.20 release. I'm also not sure it's worth spending a lot of time trying to fix this test, but I'd definitely be happy if someone proposes a different solution. > -Peff --- >8 --- Subject: [PATCH] t5570: drop racy test t5570 being racy has been reported twice separately on the mailing list [*1*, *2*]. To make the test race proof, we'd either have to introduce another fifo the test snippet is waiting on, or somehow convincing "cat" to flush (and let us know when it has). Which really implies killing the daemon, and wait()ing on cat to process the EOF and exit. And that makes the tests a lot more expensive if we have to start the daemon for each snippet. As this is a test for a relatively minor fix (according to the author) in 19136be3f8 ("daemon: fix off-by-one in logging extended attributes", 2018-01-24), drop it to avoid this racyness. It doesn't seem worth making the test code much more complex, or slowing down all tests just to keep this one. *1*: 1522783990.964448.1325338528.0D49CC15@webmail.messagingengine.com/ *2*: 9d4e5224-9ff4-f3f8-519d-7b2a6f1ea7cd@web.de Reported-by: Jan Palus <jpalus@fastmail.com> Reported-by: Torsten Bögershausen <tboegi@web.de> Helped-by: Jeff King <peff@peff.net> Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com> --- t/t5570-git-daemon.sh | 13 ------------- 1 file changed, 13 deletions(-) diff --git a/t/t5570-git-daemon.sh b/t/t5570-git-daemon.sh index 7466aad111..58ee787685 100755 --- a/t/t5570-git-daemon.sh +++ b/t/t5570-git-daemon.sh @@ -183,19 +183,6 @@ test_expect_success 'hostname cannot break out of directory' ' git ls-remote "$GIT_DAEMON_URL/escape.git" ' -test_expect_success 'daemon log records all attributes' ' - cat >expect <<-\EOF && - Extended attribute "host": localhost - Extended attribute "protocol": version=1 - EOF - >daemon.log && - GIT_OVERRIDE_VIRTUAL_HOST=localhost \ - git -c protocol.version=1 \ - ls-remote "$GIT_DAEMON_URL/interp.git" && - grep -i extended.attribute daemon.log | cut -d" " -f2- >actual && - test_cmp expect actual -' - test_expect_success FAKENC 'hostname interpolation works after LF-stripping' ' { printf "git-upload-pack /interp.git\n\0host=localhost" | packetize