git-commit-vandalism/contrib
Jeff Hostetler 9fd1902762 unix-stream-server: create unix domain socket under lock
Create a wrapper class for `unix_stream_listen()` that uses a ".lock"
lockfile to create the unix domain socket in a race-free manner.

Unix domain sockets have a fundamental problem on Unix systems because
they persist in the filesystem until they are deleted.  This is
independent of whether a server is actually listening for connections.
Well-behaved servers are expected to delete the socket when they
shutdown.  A new server cannot easily tell if a found socket is
attached to an active server or is leftover cruft from a dead server.
The traditional solution used by `unix_stream_listen()` is to force
delete the socket pathname and then create a new socket.  This solves
the latter (cruft) problem, but in the case of the former, it orphans
the existing server (by stealing the pathname associated with the
socket it is listening on).

We cannot directly use a .lock lockfile to create the socket because
the socket is created by `bind(2)` rather than the `open(2)` mechanism
used by `tempfile.c`.

As an alternative, we hold a plain lockfile ("<path>.lock") as a
mutual exclusion device.  Under the lock, we test if an existing
socket ("<path>") is has an active server.  If not, we create a new
socket and begin listening.  Then we use "rollback" to delete the
lockfile in all cases.

This wrapper code conceptually exists at a higher-level than the core
unix_stream_connect() and unix_stream_listen() routines that it
consumes.  It is isolated in a wrapper class for clarity.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-15 14:32:51 -07:00
..
buildsystems unix-stream-server: create unix domain socket under lock 2021-03-15 14:32:51 -07:00
coccinelle commit: move members graph_pos, generation to a slab 2020-06-17 14:37:30 -07:00
completion Merge branch 'fc/zsh-completion' 2020-12-08 15:11:22 -08:00
contacts git-contacts: also recognise "Reported-by:" 2017-07-27 09:42:55 -07:00
credential contrib/credential/netrc: work outside a repo 2019-12-20 12:40:52 -08:00
diff-highlight diff-highlight: correctly match blank lines for flush 2020-09-21 22:33:28 -07:00
emacs git{,-blame}.el: remove old bitrotting Emacs code 2018-04-16 17:25:49 +09:00
examples Merge branch 'bw/c-plus-plus' into ds/lazy-load-trees 2018-04-11 10:46:32 +09:00
fast-import import-tars: ignore the global PAX header 2020-03-24 14:39:47 -07:00
git-jump contrib/git-jump/git-jump: jump to exact location 2018-06-22 12:59:02 -07:00
git-shell-commands
hg-to-git hg-to-git: make it compatible with both python3 and python2 2019-09-18 12:03:05 -07:00
hooks multimail: fix a few simple spelling errors 2019-11-10 16:00:55 +09:00
long-running-filter docs: warn about possible '=' in clean/smudge filter process values 2016-12-06 11:29:52 -08:00
mw-to-git remote-mediawiki: use "sh" to eliminate unquoted commands 2020-09-21 12:37:38 -07:00
persistent-https docs/config: mention protocol implications of url.insteadOf 2017-06-01 10:07:10 +09:00
remote-helpers contrib: git-remote-{bzr,hg} placeholders don't need Python 2017-03-03 11:09:34 -08:00
stats
subtree Merge branch 'dl/subtree-docs' 2020-08-24 14:54:33 -07:00
thunderbird-patch-inline
update-unicode unicode_width.h: rename to use dash in file name 2018-04-11 18:11:00 +09:00
vscode vscode: let cSpell work on commit messages, too 2018-07-30 13:14:39 -07:00
workdir git-new-workdir: mark script as LF-only 2017-05-10 13:32:50 +09:00
coverage-diff.sh contrib: add coverage-diff script 2018-10-10 10:11:35 +09:00
git-resurrect.sh contrib/git-resurrect.sh: use hash-agnostic OID pattern 2020-10-08 11:48:56 -07:00
README
remotes2config.sh
rerere-train.sh contrib/rerere-train: optionally overwrite existing resolutions 2017-07-26 13:38:48 -07:00

Contributed Software

Although these pieces are available as part of the official git
source tree, they are in somewhat different status.  The
intention is to keep interesting tools around git here, maybe
even experimental ones, to give users an easier access to them,
and to give tools wider exposure, so that they can be improved
faster.

I am not expecting to touch these myself that much.  As far as
my day-to-day operation is concerned, these subdirectories are
owned by their respective primary authors.  I am willing to help
if users of these components and the contrib/ subtree "owners"
have technical/design issues to resolve, but the initiative to
fix and/or enhance things _must_ be on the side of the subtree
owners.  IOW, I won't be actively looking for bugs and rooms for
enhancements in them as the git maintainer -- I may only do so
just as one of the users when I want to scratch my own itch.  If
you have patches to things in contrib/ area, the patch should be
first sent to the primary author, and then the primary author
should ack and forward it to me (git pull request is nicer).
This is the same way as how I have been treating gitk, and to a
lesser degree various foreign SCM interfaces, so you know the
drill.

I expect that things that start their life in the contrib/ area
to graduate out of contrib/ once they mature, either by becoming
projects on their own, or moving to the toplevel directory.  On
the other hand, I expect I'll be proposing removal of disused
and inactive ones from time to time.

If you have new things to add to this area, please first propose
it on the git mailing list, and after a list discussion proves
there are some general interests (it does not have to be a
list-wide consensus for a tool targeted to a relatively narrow
audience -- for example I do not work with projects whose
upstream is svn, so I have no use for git-svn myself, but it is
of general interest for people who need to interoperate with SVN
repositories in a way git-svn works better than git-svnimport),
submit a patch to create a subdirectory of contrib/ and put your
stuff there.

-jc