##// END OF EJS Templates
util: implement zstd compression engine...
util: implement zstd compression engine Now that zstd is vendored and being built (in some configurations), we can implement a compression engine for zstd! The zstd engine is a little different from existing engines. Because it may not always be present, we have to defer load the module in case importing it fails. We facilitate this via a cached property that holds a reference to the module or None. The "available" method is implemented to reflect reality. The zstd engine declares its ability to handle bundles using the "zstd" human name and the "ZS" internal name. The latter was chosen because internal names are 2 characters (by only convention I think) and "ZS" seems reasonable. The engine, like others, supports specifying the compression level. However, there are no consumers of this API that yet pass in that argument. I have plans to change that, so stay tuned. Since all we need to do to support bundle generation with a new compression engine is implement and register the compression engine, bundle generation with zstd "just works!" Tests demonstrating this have been added. How does performance of zstd for bundle generation compare? On the mozilla-unified repo, `hg bundle --all -t <engine>-v2` yields the following on my i7-6700K on Linux: engine CPU time bundle size vs orig size throughput none 97.0s 4,054,405,584 100.0% 41.8 MB/s bzip2 (l=9) 393.6s 975,343,098 24.0% 10.3 MB/s gzip (l=6) 184.0s 1,140,533,074 28.1% 22.0 MB/s zstd (l=1) 108.2s 1,119,434,718 27.6% 37.5 MB/s zstd (l=2) 111.3s 1,078,328,002 26.6% 36.4 MB/s zstd (l=3) 113.7s 1,011,823,727 25.0% 35.7 MB/s zstd (l=4) 116.0s 1,008,965,888 24.9% 35.0 MB/s zstd (l=5) 121.0s 977,203,148 24.1% 33.5 MB/s zstd (l=6) 131.7s 927,360,198 22.9% 30.8 MB/s zstd (l=7) 139.0s 912,808,505 22.5% 29.2 MB/s zstd (l=12) 198.1s 854,527,714 21.1% 20.5 MB/s zstd (l=18) 681.6s 789,750,690 19.5% 5.9 MB/s On compression, zstd for bundle generation delivers: * better compression than gzip with significantly less CPU utilization * better than bzip2 compression ratios while still being significantly faster than gzip * ability to aggressively tune compression level to achieve significantly smaller bundles That last point is important. With clone bundles, a server can pre-generate a bundle file, upload it to a static file server, and redirect clients to transparently download it during clone. The server could choose to produce a zstd bundle with the highest compression settings possible. This would take a very long time - a magnitude longer than a typical zstd bundle generation - but the result would be hundreds of megabytes smaller! For the clone volume we do at Mozilla, this could translate to petabytes of bandwidth savings per year and faster clones (due to smaller transfer size). I don't have detailed numbers to report on decompression. However, zstd decompression is fast: >1 GB/s output throughput on this machine, even through the Python bindings. And it can do that regardless of the compression level of the input. By the time you have enough data to worry about overhead of decompression, you have plenty of other things to worry about performance wise. zstd is wins all around. I can't wait to implement support for it on the wire protocol and in revlogs.

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hg-ssh
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#!/usr/bin/env python
#
# Copyright 2005-2007 by Intevation GmbH <intevation@intevation.de>
#
# Author(s):
# Thomas Arendsen Hein <thomas@intevation.de>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""
hg-ssh - a wrapper for ssh access to a limited set of mercurial repos
To be used in ~/.ssh/authorized_keys with the "command" option, see sshd(8):
command="hg-ssh path/to/repo1 /path/to/repo2 ~/repo3 ~user/repo4" ssh-dss ...
(probably together with these other useful options:
no-port-forwarding,no-X11-forwarding,no-agent-forwarding)
This allows pull/push over ssh from/to the repositories given as arguments.
If all your repositories are subdirectories of a common directory, you can
allow shorter paths with:
command="cd path/to/my/repositories && hg-ssh repo1 subdir/repo2"
You can use pattern matching of your normal shell, e.g.:
command="cd repos && hg-ssh user/thomas/* projects/{mercurial,foo}"
You can also add a --read-only flag to allow read-only access to a key, e.g.:
command="hg-ssh --read-only repos/*"
"""
# enable importing on demand to reduce startup time
from mercurial import demandimport; demandimport.enable()
from mercurial import dispatch
import sys, os, shlex
def main():
cwd = os.getcwd()
readonly = False
args = sys.argv[1:]
while len(args):
if args[0] == '--read-only':
readonly = True
args.pop(0)
else:
break
allowed_paths = [os.path.normpath(os.path.join(cwd,
os.path.expanduser(path)))
for path in args]
orig_cmd = os.getenv('SSH_ORIGINAL_COMMAND', '?')
try:
cmdargv = shlex.split(orig_cmd)
except ValueError as e:
sys.stderr.write('Illegal command "%s": %s\n' % (orig_cmd, e))
sys.exit(255)
if cmdargv[:2] == ['hg', '-R'] and cmdargv[3:] == ['serve', '--stdio']:
path = cmdargv[2]
repo = os.path.normpath(os.path.join(cwd, os.path.expanduser(path)))
if repo in allowed_paths:
cmd = ['-R', repo, 'serve', '--stdio']
if readonly:
cmd += [
'--config',
'hooks.pretxnopen.hg-ssh=python:__main__.rejectpush',
'--config',
'hooks.prepushkey.hg-ssh=python:__main__.rejectpush'
]
dispatch.dispatch(dispatch.request(cmd))
else:
sys.stderr.write('Illegal repository "%s"\n' % repo)
sys.exit(255)
else:
sys.stderr.write('Illegal command "%s"\n' % orig_cmd)
sys.exit(255)
def rejectpush(ui, **kwargs):
ui.warn(("Permission denied\n"))
# mercurial hooks use unix process conventions for hook return values
# so a truthy return means failure
return True
if __name__ == '__main__':
main()