Previously, I've observed bugs where we either:
1) Exit too early, leaving undownloaded objects
2) Hang while downloading
This rewrite hopefully fixes both.
This counts as an implicit "hold" on the first items, which we must
complete. Otherwise there are race conditions where the queue may
signal idle when in fact the main process is still working.
We were blocking for easily 1/10 or 1/5 of a second in fdatasync(),
which drastically slows down the whole process.
This threading isn't quite as good as the ostree-pull command, but it
lets us avoid the dependency on libsoup everywhere, and it's simpler.
This gives us something closer to the advantages of archive and
archive-z when using the latter. Concretely we get deduplication
among multiple checkouts, along with the "devino" hash table trick
during commits to avoid checksumming content again.
This is enabled by default.
Create a worker thread for processing metadata, reserving the main
thread for HTTP requests.
This can create a very significant efficiency win for large pull
requests since we are much more likely to keep a full pipeline open.
The status display is also nicer now.
I run builds on my laptop, but it also crashes about 1/4 of the time
while suspending. It's definitely undesrirable to get e.g. empty
.dirtree objects because they corrupt builds. Concretely, I was
getting empty contents committed for xorg-util-macros.
Now, we used to write out temporary files using g_file_replace() which
does a fsync() during close, but then switched to a more "manual"
g_file_append_to().
We could switch back to g_file_replace(), but the problem is, we don't
want to call fsync() on temporary files in the case where we already
have the object. Attempting to add an object we already have is a
*very* common case.
This is both the old and new code sequence for the case where an
object is already stored:
open(temp, O_WRONLY)
write() write() write()
close()
lstat(objects/3a/9fe332...) = 0
unlink(temp)
In the *new* code, here's the case where an object *isn't* stored:
open(temp, O_WRONLY)
write() write() write()
close()
lstat(objects/3a/9fe332...) = -1
open(temp, O_RDONLY)
fdatasync()
close()
rename(temp, objects/3a/9fe332)
Compare with the *old* code path for when an object isn't stored:
open(temp, O_WRONLY)
write() write() write()
close()
lstat(objects/3a/9fe332...) = -1
link(temp, objects/3a/9fe332)
unlink(temp)
The problem with this is we really need to fdatasync(). Also doing
just rename() instead of the weird link()/unlink() helps us express to
the filesystem that we want atomic semantics. For example, BTRFS has
special handling for rename().
The qemu helper really wants to copy kernel modules, but not
update the system bootloader. Allow it to reuse ostadmin for
this.
Note that our previous path of shelling out to "cp -al" broke because
it refused to make cross-device links.
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# On branch master
# Your branch is ahead of 'origin/master' by 1 commit.
#
# Changes to be committed:
# (use "git reset HEAD <file>..." to unstage)
#
# modified: src/libotutil/ot-gio-utils.c
# modified: src/libotutil/ot-gio-utils.h
# modified: src/ostadmin/ot-admin-builtin-deploy.c
#
# Untracked files:
# (use "git add <file>..." to include in what will be committed)
#
# embedded-dependencies/glib/
# embedded-dependencies/libsoup/
Colin Walters