wireproto: add streams to frame-based protocol
Previously, the frame-based protocol was just a series of frames,
with each frame associated with a request ID.
In order to scale the protocol, we'll want to enable the use of
compression. While it is possible to enable compression at the
socket/pipe level, this has its disadvantages. The big one is it
undermines the point of frames being standalone, atomic units that
can be read and written: if you add compression above the framing
protocol, you are back to having a stream-based protocol as opposed
to something frame-based.
So in order to preserve frames, compression needs to occur at
the frame payload level.
Compressing each frame's payload individually will limit compression
ratios because the window size of the compressor will be limited
by the max frame size, which is 32-64kb as currently defined. It
will also add CPU overhead, as it is more efficient for compressors
to operate on fewer, larger blocks of data than more, smaller blocks.
So compressing each frame independently is out.
This means we need to compress each frame's payload as if it is part
of a larger stream.
The simplest approach is to have 1 stream per connection. This
could certainly work. However, it has disadvantages (documented below).
We could also have 1 stream per RPC/command invocation. (This is the
model HTTP/2 goes with.) This also has disadvantages.
The main disadvantage to one global stream is that it has the very
real potential to create CPU bottlenecks doing compression. Networks
are only getting faster and the performance of single CPU cores has
been relatively flat. Newer compression formats like zstandard offer
better CPU cycle efficiency than predecessors like zlib. But it still
all too common to saturate your CPU with compression overhead long
before you saturate the network pipe.
The main disadvantage with streams per request is that you can't
reap the benefits of the compression context for multiple requests.
For example, if you send 1000 RPC requests (or HTTP/2 requests for
that matter), the response to each would have its own compression
context. The overall size of the raw responses would be larger because
compression contexts wouldn't be able to reference data from another
request or response.
The approach for streams as implemented in this commit is to support
N streams per connection and for streams to potentially span requests
and responses. As explained by the added internals docs, this
facilitates servers and clients delegating independent streams and
compression to independent threads / CPU cores. This helps alleviate
the CPU bottleneck of compression. This design also allows compression
contexts to be reused across requests/responses. This can result in
improved compression ratios and less overhead for compressors and
decompressors having to build new contexts.
Another feature that was defined was the ability for individual frames
within a stream to declare whether that individual frame's payload
uses the content encoding (read: compression) defined by the stream.
The idea here is that some servers may serve data from a combination
of caches and dynamic resolution. Data coming from caches may be
pre-compressed. We want to facilitate servers being able to essentially
stream bytes from caches to the wire with minimal overhead. Being
able to mix and match with frames are compressed within a stream
enables these types of advanced server functionality.
This commit defines the new streams mechanism. Basic code for
supporting streams in frames has been added. But that code is
seriously lacking and doesn't fully conform to the defined protocol.
For example, we don't close any streams. And support for content
encoding within streams is not yet implemented. The change was
rather invasive and I didn't think it would be reasonable to implement
the entire feature in a single commit.
For the record, I would have loved to reuse an existing multiplexing
protocol to build the new wire protocol on top of. However, I couldn't
find a protocol that offers the performance and scaling characteristics
that I desired. Namely, it should support multiple compression
contexts to facilitate scaling out to multiple CPU cores and
compression contexts should be able to live longer than single RPC
requests. HTTP/2 *almost* fits the bill. But the semantics of HTTP
message exchange state that streams can only live for a single
request-response. We /could/ tunnel on top of HTTP/2 streams and
frames with HEADER and DATA frames. But there's no guarantee that
HTTP/2 libraries and proxies would allow us to use HTTP/2 streams
and frames without the HTTP message exchange semantics defined in
RFC 7540 Section 8. Other RPC protocols like gRPC tunnel are built
on top of HTTP/2 and thus preserve its semantics of stream per
RPC invocation. Even QUIC does this. We could attempt to invent a
higher-level stream that spans HTTP/2 streams. But this would be
violating HTTP/2 because there is no guarantee that HTTP/2 streams
are routed to the same server. The best we can do - which is what
this protocol does - is shoehorn all request and response data into
a single HTTP message and create streams within. At that point, we've
defined a Content-Type in HTTP parlance. It just so happens our
media type can also work as a standalone, stream-based protocol,
without leaning on HTTP or similar protocol.
Differential Revision: https://phab.mercurial-scm.org/D2907
from __future__ import absolute_import
import errno
import os
import re
import socket
import stat
import subprocess
import sys
import tempfile
tempprefix = 'hg-hghave-'
checks = {
"true": (lambda: True, "yak shaving"),
"false": (lambda: False, "nail clipper"),
}
def check(name, desc):
"""Registers a check function for a feature."""
def decorator(func):
checks[name] = (func, desc)
return func
return decorator
def checkvers(name, desc, vers):
"""Registers a check function for each of a series of versions.
vers can be a list or an iterator"""
def decorator(func):
def funcv(v):
def f():
return func(v)
return f
for v in vers:
v = str(v)
f = funcv(v)
checks['%s%s' % (name, v.replace('.', ''))] = (f, desc % v)
return func
return decorator
def checkfeatures(features):
result = {
'error': [],
'missing': [],
'skipped': [],
}
for feature in features:
negate = feature.startswith('no-')
if negate:
feature = feature[3:]
if feature not in checks:
result['missing'].append(feature)
continue
check, desc = checks[feature]
try:
available = check()
except Exception:
result['error'].append('hghave check failed: %s' % feature)
continue
if not negate and not available:
result['skipped'].append('missing feature: %s' % desc)
elif negate and available:
result['skipped'].append('system supports %s' % desc)
return result
def require(features):
"""Require that features are available, exiting if not."""
result = checkfeatures(features)
for missing in result['missing']:
sys.stderr.write('skipped: unknown feature: %s\n' % missing)
for msg in result['skipped']:
sys.stderr.write('skipped: %s\n' % msg)
for msg in result['error']:
sys.stderr.write('%s\n' % msg)
if result['missing']:
sys.exit(2)
if result['skipped'] or result['error']:
sys.exit(1)
def matchoutput(cmd, regexp, ignorestatus=False):
"""Return the match object if cmd executes successfully and its output
is matched by the supplied regular expression.
"""
r = re.compile(regexp)
try:
p = subprocess.Popen(
cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
except OSError as e:
if e.errno != errno.ENOENT:
raise
ret = -1
ret = p.wait()
s = p.stdout.read()
return (ignorestatus or not ret) and r.search(s)
@check("baz", "GNU Arch baz client")
def has_baz():
return matchoutput('baz --version 2>&1', br'baz Bazaar version')
@check("bzr", "Canonical's Bazaar client")
def has_bzr():
try:
import bzrlib
import bzrlib.bzrdir
import bzrlib.errors
import bzrlib.revision
import bzrlib.revisionspec
bzrlib.revisionspec.RevisionSpec
return bzrlib.__doc__ is not None
except (AttributeError, ImportError):
return False
@checkvers("bzr", "Canonical's Bazaar client >= %s", (1.14,))
def has_bzr_range(v):
major, minor = v.split('.')[0:2]
try:
import bzrlib
return (bzrlib.__doc__ is not None
and bzrlib.version_info[:2] >= (int(major), int(minor)))
except ImportError:
return False
@check("chg", "running with chg")
def has_chg():
return 'CHGHG' in os.environ
@check("cvs", "cvs client/server")
def has_cvs():
re = br'Concurrent Versions System.*?server'
return matchoutput('cvs --version 2>&1', re) and not has_msys()
@check("cvs112", "cvs client/server 1.12.* (not cvsnt)")
def has_cvs112():
re = br'Concurrent Versions System \(CVS\) 1.12.*?server'
return matchoutput('cvs --version 2>&1', re) and not has_msys()
@check("cvsnt", "cvsnt client/server")
def has_cvsnt():
re = br'Concurrent Versions System \(CVSNT\) (\d+).(\d+).*\(client/server\)'
return matchoutput('cvsnt --version 2>&1', re)
@check("darcs", "darcs client")
def has_darcs():
return matchoutput('darcs --version', br'\b2\.([2-9]|\d{2})', True)
@check("mtn", "monotone client (>= 1.0)")
def has_mtn():
return matchoutput('mtn --version', br'monotone', True) and not matchoutput(
'mtn --version', br'monotone 0\.', True)
@check("eol-in-paths", "end-of-lines in paths")
def has_eol_in_paths():
try:
fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix, suffix='\n\r')
os.close(fd)
os.remove(path)
return True
except (IOError, OSError):
return False
@check("execbit", "executable bit")
def has_executablebit():
try:
EXECFLAGS = stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
fh, fn = tempfile.mkstemp(dir='.', prefix=tempprefix)
try:
os.close(fh)
m = os.stat(fn).st_mode & 0o777
new_file_has_exec = m & EXECFLAGS
os.chmod(fn, m ^ EXECFLAGS)
exec_flags_cannot_flip = ((os.stat(fn).st_mode & 0o777) == m)
finally:
os.unlink(fn)
except (IOError, OSError):
# we don't care, the user probably won't be able to commit anyway
return False
return not (new_file_has_exec or exec_flags_cannot_flip)
@check("icasefs", "case insensitive file system")
def has_icasefs():
# Stolen from mercurial.util
fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix)
os.close(fd)
try:
s1 = os.stat(path)
d, b = os.path.split(path)
p2 = os.path.join(d, b.upper())
if path == p2:
p2 = os.path.join(d, b.lower())
try:
s2 = os.stat(p2)
return s2 == s1
except OSError:
return False
finally:
os.remove(path)
@check("fifo", "named pipes")
def has_fifo():
if getattr(os, "mkfifo", None) is None:
return False
name = tempfile.mktemp(dir='.', prefix=tempprefix)
try:
os.mkfifo(name)
os.unlink(name)
return True
except OSError:
return False
@check("killdaemons", 'killdaemons.py support')
def has_killdaemons():
return True
@check("cacheable", "cacheable filesystem")
def has_cacheable_fs():
from mercurial import util
fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix)
os.close(fd)
try:
return util.cachestat(path).cacheable()
finally:
os.remove(path)
@check("lsprof", "python lsprof module")
def has_lsprof():
try:
import _lsprof
_lsprof.Profiler # silence unused import warning
return True
except ImportError:
return False
def gethgversion():
m = matchoutput('hg --version --quiet 2>&1', br'(\d+)\.(\d+)')
if not m:
return (0, 0)
return (int(m.group(1)), int(m.group(2)))
@checkvers("hg", "Mercurial >= %s",
list([(1.0 * x) / 10 for x in range(9, 99)]))
def has_hg_range(v):
major, minor = v.split('.')[0:2]
return gethgversion() >= (int(major), int(minor))
@check("hg08", "Mercurial >= 0.8")
def has_hg08():
if checks["hg09"][0]():
return True
return matchoutput('hg help annotate 2>&1', '--date')
@check("hg07", "Mercurial >= 0.7")
def has_hg07():
if checks["hg08"][0]():
return True
return matchoutput('hg --version --quiet 2>&1', 'Mercurial Distributed SCM')
@check("hg06", "Mercurial >= 0.6")
def has_hg06():
if checks["hg07"][0]():
return True
return matchoutput('hg --version --quiet 2>&1', 'Mercurial version')
@check("gettext", "GNU Gettext (msgfmt)")
def has_gettext():
return matchoutput('msgfmt --version', br'GNU gettext-tools')
@check("git", "git command line client")
def has_git():
return matchoutput('git --version 2>&1', br'^git version')
def getgitversion():
m = matchoutput('git --version 2>&1', br'git version (\d+)\.(\d+)')
if not m:
return (0, 0)
return (int(m.group(1)), int(m.group(2)))
# https://github.com/git-lfs/lfs-test-server
@check("lfs-test-server", "git-lfs test server")
def has_lfsserver():
exe = 'lfs-test-server'
if has_windows():
exe = 'lfs-test-server.exe'
return any(
os.access(os.path.join(path, exe), os.X_OK)
for path in os.environ["PATH"].split(os.pathsep)
)
@checkvers("git", "git client (with ext::sh support) version >= %s", (1.9,))
def has_git_range(v):
major, minor = v.split('.')[0:2]
return getgitversion() >= (int(major), int(minor))
@check("docutils", "Docutils text processing library")
def has_docutils():
try:
import docutils.core
docutils.core.publish_cmdline # silence unused import
return True
except ImportError:
return False
def getsvnversion():
m = matchoutput('svn --version --quiet 2>&1', br'^(\d+)\.(\d+)')
if not m:
return (0, 0)
return (int(m.group(1)), int(m.group(2)))
@checkvers("svn", "subversion client and admin tools >= %s", (1.3, 1.5))
def has_svn_range(v):
major, minor = v.split('.')[0:2]
return getsvnversion() >= (int(major), int(minor))
@check("svn", "subversion client and admin tools")
def has_svn():
return matchoutput('svn --version 2>&1', br'^svn, version') and \
matchoutput('svnadmin --version 2>&1', br'^svnadmin, version')
@check("svn-bindings", "subversion python bindings")
def has_svn_bindings():
try:
import svn.core
version = svn.core.SVN_VER_MAJOR, svn.core.SVN_VER_MINOR
if version < (1, 4):
return False
return True
except ImportError:
return False
@check("p4", "Perforce server and client")
def has_p4():
return (matchoutput('p4 -V', br'Rev\. P4/') and
matchoutput('p4d -V', br'Rev\. P4D/'))
@check("symlink", "symbolic links")
def has_symlink():
if getattr(os, "symlink", None) is None:
return False
name = tempfile.mktemp(dir='.', prefix=tempprefix)
try:
os.symlink(".", name)
os.unlink(name)
return True
except (OSError, AttributeError):
return False
@check("hardlink", "hardlinks")
def has_hardlink():
from mercurial import util
fh, fn = tempfile.mkstemp(dir='.', prefix=tempprefix)
os.close(fh)
name = tempfile.mktemp(dir='.', prefix=tempprefix)
try:
util.oslink(fn, name)
os.unlink(name)
return True
except OSError:
return False
finally:
os.unlink(fn)
@check("hardlink-whitelisted", "hardlinks on whitelisted filesystems")
def has_hardlink_whitelisted():
from mercurial import util
try:
fstype = util.getfstype(b'.')
except OSError:
return False
return fstype in util._hardlinkfswhitelist
@check("rmcwd", "can remove current working directory")
def has_rmcwd():
ocwd = os.getcwd()
temp = tempfile.mkdtemp(dir='.', prefix=tempprefix)
try:
os.chdir(temp)
# On Linux, 'rmdir .' isn't allowed, but the other names are okay.
# On Solaris and Windows, the cwd can't be removed by any names.
os.rmdir(os.getcwd())
return True
except OSError:
return False
finally:
os.chdir(ocwd)
# clean up temp dir on platforms where cwd can't be removed
try:
os.rmdir(temp)
except OSError:
pass
@check("tla", "GNU Arch tla client")
def has_tla():
return matchoutput('tla --version 2>&1', br'The GNU Arch Revision')
@check("gpg", "gpg client")
def has_gpg():
return matchoutput('gpg --version 2>&1', br'GnuPG')
@check("gpg2", "gpg client v2")
def has_gpg2():
return matchoutput('gpg --version 2>&1', br'GnuPG[^0-9]+2\.')
@check("gpg21", "gpg client v2.1+")
def has_gpg21():
return matchoutput('gpg --version 2>&1', br'GnuPG[^0-9]+2\.(?!0)')
@check("unix-permissions", "unix-style permissions")
def has_unix_permissions():
d = tempfile.mkdtemp(dir='.', prefix=tempprefix)
try:
fname = os.path.join(d, 'foo')
for umask in (0o77, 0o07, 0o22):
os.umask(umask)
f = open(fname, 'w')
f.close()
mode = os.stat(fname).st_mode
os.unlink(fname)
if mode & 0o777 != ~umask & 0o666:
return False
return True
finally:
os.rmdir(d)
@check("unix-socket", "AF_UNIX socket family")
def has_unix_socket():
return getattr(socket, 'AF_UNIX', None) is not None
@check("root", "root permissions")
def has_root():
return getattr(os, 'geteuid', None) and os.geteuid() == 0
@check("pyflakes", "Pyflakes python linter")
def has_pyflakes():
return matchoutput("sh -c \"echo 'import re' 2>&1 | pyflakes\"",
br"<stdin>:1: 're' imported but unused",
True)
@check("pylint", "Pylint python linter")
def has_pylint():
return matchoutput("pylint --help",
br"Usage: pylint",
True)
@check("clang-format", "clang-format C code formatter")
def has_clang_format():
return matchoutput("clang-format --help",
br"^OVERVIEW: A tool to format C/C\+\+[^ ]+ code.")
@check("jshint", "JSHint static code analysis tool")
def has_jshint():
return matchoutput("jshint --version 2>&1", br"jshint v")
@check("pygments", "Pygments source highlighting library")
def has_pygments():
try:
import pygments
pygments.highlight # silence unused import warning
return True
except ImportError:
return False
@check("outer-repo", "outer repo")
def has_outer_repo():
# failing for other reasons than 'no repo' imply that there is a repo
return not matchoutput('hg root 2>&1',
br'abort: no repository found', True)
@check("ssl", "ssl module available")
def has_ssl():
try:
import ssl
ssl.CERT_NONE
return True
except ImportError:
return False
@check("sslcontext", "python >= 2.7.9 ssl")
def has_sslcontext():
try:
import ssl
ssl.SSLContext
return True
except (ImportError, AttributeError):
return False
@check("defaultcacerts", "can verify SSL certs by system's CA certs store")
def has_defaultcacerts():
from mercurial import sslutil, ui as uimod
ui = uimod.ui.load()
return sslutil._defaultcacerts(ui) or sslutil._canloaddefaultcerts
@check("defaultcacertsloaded", "detected presence of loaded system CA certs")
def has_defaultcacertsloaded():
import ssl
from mercurial import sslutil, ui as uimod
if not has_defaultcacerts():
return False
if not has_sslcontext():
return False
ui = uimod.ui.load()
cafile = sslutil._defaultcacerts(ui)
ctx = ssl.create_default_context()
if cafile:
ctx.load_verify_locations(cafile=cafile)
else:
ctx.load_default_certs()
return len(ctx.get_ca_certs()) > 0
@check("tls1.2", "TLS 1.2 protocol support")
def has_tls1_2():
from mercurial import sslutil
return 'tls1.2' in sslutil.supportedprotocols
@check("windows", "Windows")
def has_windows():
return os.name == 'nt'
@check("system-sh", "system() uses sh")
def has_system_sh():
return os.name != 'nt'
@check("serve", "platform and python can manage 'hg serve -d'")
def has_serve():
return True
@check("test-repo", "running tests from repository")
def has_test_repo():
t = os.environ["TESTDIR"]
return os.path.isdir(os.path.join(t, "..", ".hg"))
@check("tic", "terminfo compiler and curses module")
def has_tic():
try:
import curses
curses.COLOR_BLUE
return matchoutput('test -x "`which tic`"', br'')
except ImportError:
return False
@check("msys", "Windows with MSYS")
def has_msys():
return os.getenv('MSYSTEM')
@check("aix", "AIX")
def has_aix():
return sys.platform.startswith("aix")
@check("osx", "OS X")
def has_osx():
return sys.platform == 'darwin'
@check("osxpackaging", "OS X packaging tools")
def has_osxpackaging():
try:
return (matchoutput('pkgbuild', br'Usage: pkgbuild ', ignorestatus=1)
and matchoutput(
'productbuild', br'Usage: productbuild ',
ignorestatus=1)
and matchoutput('lsbom', br'Usage: lsbom', ignorestatus=1)
and matchoutput(
'xar --help', br'Usage: xar', ignorestatus=1))
except ImportError:
return False
@check('linuxormacos', 'Linux or MacOS')
def has_linuxormacos():
# This isn't a perfect test for MacOS. But it is sufficient for our needs.
return sys.platform.startswith(('linux', 'darwin'))
@check("docker", "docker support")
def has_docker():
pat = br'A self-sufficient runtime for'
if matchoutput('docker --help', pat):
if 'linux' not in sys.platform:
# TODO: in theory we should be able to test docker-based
# package creation on non-linux using boot2docker, but in
# practice that requires extra coordination to make sure
# $TESTTEMP is going to be visible at the same path to the
# boot2docker VM. If we figure out how to verify that, we
# can use the following instead of just saying False:
# return 'DOCKER_HOST' in os.environ
return False
return True
return False
@check("debhelper", "debian packaging tools")
def has_debhelper():
# Some versions of dpkg say `dpkg', some say 'dpkg' (` vs ' on the first
# quote), so just accept anything in that spot.
dpkg = matchoutput('dpkg --version',
br"Debian .dpkg' package management program")
dh = matchoutput('dh --help',
br'dh is a part of debhelper.', ignorestatus=True)
dh_py2 = matchoutput('dh_python2 --help',
br'other supported Python versions')
# debuild comes from the 'devscripts' package, though you might want
# the 'build-debs' package instead, which has a dependency on devscripts.
debuild = matchoutput('debuild --help',
br'to run debian/rules with given parameter')
return dpkg and dh and dh_py2 and debuild
@check("debdeps",
"debian build dependencies (run dpkg-checkbuilddeps in contrib/)")
def has_debdeps():
# just check exit status (ignoring output)
path = '%s/../contrib/debian/control' % os.environ['TESTDIR']
return matchoutput('dpkg-checkbuilddeps %s' % path, br'')
@check("demandimport", "demandimport enabled")
def has_demandimport():
# chg disables demandimport intentionally for performance wins.
return ((not has_chg()) and os.environ.get('HGDEMANDIMPORT') != 'disable')
@check("py3k", "running with Python 3.x")
def has_py3k():
return 3 == sys.version_info[0]
@check("py3exe", "a Python 3.x interpreter is available")
def has_python3exe():
return 'PYTHON3' in os.environ
@check("py3pygments", "Pygments available on Python 3.x")
def has_py3pygments():
if has_py3k():
return has_pygments()
elif has_python3exe():
# just check exit status (ignoring output)
py3 = os.environ['PYTHON3']
return matchoutput('%s -c "import pygments"' % py3, br'')
return False
@check("pure", "running with pure Python code")
def has_pure():
return any([
os.environ.get("HGMODULEPOLICY") == "py",
os.environ.get("HGTEST_RUN_TESTS_PURE") == "--pure",
])
@check("slow", "allow slow tests (use --allow-slow-tests)")
def has_slow():
return os.environ.get('HGTEST_SLOW') == 'slow'
@check("hypothesis", "Hypothesis automated test generation")
def has_hypothesis():
try:
import hypothesis
hypothesis.given
return True
except ImportError:
return False
@check("unziplinks", "unzip(1) understands and extracts symlinks")
def unzip_understands_symlinks():
return matchoutput('unzip --help', br'Info-ZIP')
@check("zstd", "zstd Python module available")
def has_zstd():
try:
import mercurial.zstd
mercurial.zstd.__version__
return True
except ImportError:
return False
@check("devfull", "/dev/full special file")
def has_dev_full():
return os.path.exists('/dev/full')
@check("virtualenv", "Python virtualenv support")
def has_virtualenv():
try:
import virtualenv
virtualenv.ACTIVATE_SH
return True
except ImportError:
return False
@check("fsmonitor", "running tests with fsmonitor")
def has_fsmonitor():
return 'HGFSMONITOR_TESTS' in os.environ
@check("fuzzywuzzy", "Fuzzy string matching library")
def has_fuzzywuzzy():
try:
import fuzzywuzzy
fuzzywuzzy.__version__
return True
except ImportError:
return False
@check("clang-libfuzzer", "clang new enough to include libfuzzer")
def has_clang_libfuzzer():
mat = matchoutput('clang --version', b'clang version (\d)')
if mat:
# libfuzzer is new in clang 6
return int(mat.group(1)) > 5
return False
@check("xdiff", "xdiff algorithm")
def has_xdiff():
try:
from mercurial import policy
bdiff = policy.importmod('bdiff')
return bdiff.xdiffblocks(b'', b'') == [(0, 0, 0, 0)]
except (ImportError, AttributeError):
return False