git/git-remote-testgit.py
Pete Wyckoff 7fb8e163bd git-remote-testgit: fix race when spawning fast-import
Test "pushing to local repo" in t5800-remote-helpers can hang
due to a race condition in git-remote-testgit.  Fix it by
setting stdin to unbuffered.

On the writer side, "git push" invokes push_refs_with_export(),
which sends to stdout the command "export\n" and immediately
starts up "git fast-export".  The latter writes its output stream
to the same stdout.

On the reader side, remote helper "git-remote-testgit" reads from
stdin to get its next command.  It uses getc() to read characters
from libc up until \n.  Libc has buffered a potentially much
larger chunk of stdin.  When it sees the "export\n" command, it
forks "git fast-import" to read the stream.

If fast-export finishes before git fast-import starts, the
fast-export output can end up in libc's buffer in
git-remote-testgit, rather than in git fast-import.  The latter
hangs indefinitely on a now-empty stdin.

Signed-off-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-04-24 14:54:24 -07:00

273 lines
6.1 KiB
Python

#!/usr/bin/env python
# This command is a simple remote-helper, that is used both as a
# testcase for the remote-helper functionality, and as an example to
# show remote-helper authors one possible implementation.
#
# This is a Git <-> Git importer/exporter, that simply uses git
# fast-import and git fast-export to consume and produce fast-import
# streams.
#
# To understand better the way things work, one can activate debug
# traces by setting (to any value) the environment variables
# GIT_TRANSPORT_HELPER_DEBUG and GIT_DEBUG_TESTGIT, to see messages
# from the transport-helper side, or from this example remote-helper.
# hashlib is only available in python >= 2.5
try:
import hashlib
_digest = hashlib.sha1
except ImportError:
import sha
_digest = sha.new
import sys
import os
import time
sys.path.insert(0, os.getenv("GITPYTHONLIB","."))
from git_remote_helpers.util import die, debug, warn
from git_remote_helpers.git.repo import GitRepo
from git_remote_helpers.git.exporter import GitExporter
from git_remote_helpers.git.importer import GitImporter
from git_remote_helpers.git.non_local import NonLocalGit
def get_repo(alias, url):
"""Returns a git repository object initialized for usage.
"""
repo = GitRepo(url)
repo.get_revs()
repo.get_head()
hasher = _digest()
hasher.update(repo.path)
repo.hash = hasher.hexdigest()
repo.get_base_path = lambda base: os.path.join(
base, 'info', 'fast-import', repo.hash)
prefix = 'refs/testgit/%s/' % alias
debug("prefix: '%s'", prefix)
repo.gitdir = os.environ["GIT_DIR"]
repo.alias = alias
repo.prefix = prefix
repo.exporter = GitExporter(repo)
repo.importer = GitImporter(repo)
repo.non_local = NonLocalGit(repo)
return repo
def local_repo(repo, path):
"""Returns a git repository object initalized for usage.
"""
local = GitRepo(path)
local.non_local = None
local.gitdir = repo.gitdir
local.alias = repo.alias
local.prefix = repo.prefix
local.hash = repo.hash
local.get_base_path = repo.get_base_path
local.exporter = GitExporter(local)
local.importer = GitImporter(local)
return local
def do_capabilities(repo, args):
"""Prints the supported capabilities.
"""
print "import"
print "export"
print "refspec refs/heads/*:%s*" % repo.prefix
dirname = repo.get_base_path(repo.gitdir)
if not os.path.exists(dirname):
os.makedirs(dirname)
path = os.path.join(dirname, 'testgit.marks')
print "*export-marks %s" % path
if os.path.exists(path):
print "*import-marks %s" % path
print # end capabilities
def do_list(repo, args):
"""Lists all known references.
Bug: This will always set the remote head to master for non-local
repositories, since we have no way of determining what the remote
head is at clone time.
"""
for ref in repo.revs:
debug("? refs/heads/%s", ref)
print "? refs/heads/%s" % ref
if repo.head:
debug("@refs/heads/%s HEAD" % repo.head)
print "@refs/heads/%s HEAD" % repo.head
else:
debug("@refs/heads/master HEAD")
print "@refs/heads/master HEAD"
print # end list
def update_local_repo(repo):
"""Updates (or clones) a local repo.
"""
if repo.local:
return repo
path = repo.non_local.clone(repo.gitdir)
repo.non_local.update(repo.gitdir)
repo = local_repo(repo, path)
return repo
def do_import(repo, args):
"""Exports a fast-import stream from testgit for git to import.
"""
if len(args) != 1:
die("Import needs exactly one ref")
if not repo.gitdir:
die("Need gitdir to import")
ref = args[0]
refs = [ref]
while True:
line = sys.stdin.readline()
if line == '\n':
break
if not line.startswith('import '):
die("Expected import line.")
# strip of leading 'import '
ref = line[7:].strip()
refs.append(ref)
repo = update_local_repo(repo)
repo.exporter.export_repo(repo.gitdir, refs)
print "done"
def do_export(repo, args):
"""Imports a fast-import stream from git to testgit.
"""
if not repo.gitdir:
die("Need gitdir to export")
update_local_repo(repo)
changed = repo.importer.do_import(repo.gitdir)
if not repo.local:
repo.non_local.push(repo.gitdir)
for ref in changed:
print "ok %s" % ref
print
COMMANDS = {
'capabilities': do_capabilities,
'list': do_list,
'import': do_import,
'export': do_export,
}
def sanitize(value):
"""Cleans up the url.
"""
if value.startswith('testgit::'):
value = value[9:]
return value
def read_one_line(repo):
"""Reads and processes one command.
"""
sleepy = os.environ.get("GIT_REMOTE_TESTGIT_SLEEPY")
if sleepy:
debug("Sleeping %d sec before readline" % int(sleepy))
time.sleep(int(sleepy))
line = sys.stdin.readline()
cmdline = line
if not cmdline:
warn("Unexpected EOF")
return False
cmdline = cmdline.strip().split()
if not cmdline:
# Blank line means we're about to quit
return False
cmd = cmdline.pop(0)
debug("Got command '%s' with args '%s'", cmd, ' '.join(cmdline))
if cmd not in COMMANDS:
die("Unknown command, %s", cmd)
func = COMMANDS[cmd]
func(repo, cmdline)
sys.stdout.flush()
return True
def main(args):
"""Starts a new remote helper for the specified repository.
"""
if len(args) != 3:
die("Expecting exactly three arguments.")
sys.exit(1)
if os.getenv("GIT_DEBUG_TESTGIT"):
import git_remote_helpers.util
git_remote_helpers.util.DEBUG = True
alias = sanitize(args[1])
url = sanitize(args[2])
if not alias.isalnum():
warn("non-alnum alias '%s'", alias)
alias = "tmp"
args[1] = alias
args[2] = url
repo = get_repo(alias, url)
debug("Got arguments %s", args[1:])
more = True
sys.stdin = os.fdopen(sys.stdin.fileno(), 'r', 0)
while (more):
more = read_one_line(repo)
if __name__ == '__main__':
sys.exit(main(sys.argv))