Mercurial > hg
view i18n/hggettext @ 40022:33eb670e2834
wireprotov2: define semantics for content redirects
When I implemented the clonebundles feature and deployed it on
hg.mozilla.org using Amazon S3 as a content server, server-side CPU
and bandwidth usage dropped off a cliff and a ton of server scaling
headaches went away pretty much the instant clients with support for
clonebundles were rolled out to Firefox CI.
An obvious takeaway from that experience was that offloading server
load to scalable file servers - potentially backed by a CDN - is a
really good idea. Another takeaway was that Mercurial's wire protocol
wasn't in a good position to support data offload generally.
In wire protocol version 1, there isn't a mechanism in the protocol to
say "grab the data from over here instead." For HTTP, we could teach
the client to follow HTTP redirects. Or we could invent a media type
that encoded redirects inline. But for SSH, we were pretty much out of
luck because that protocol wasn't very flexible.
Wire protocol version 2 offers the opportunity to do something better.
The recent generic server-side content caching layer in the wire
protocol version 2 server demonstrated that it is possible to have
drop-in caching of responses to command requests. This by itself
adds tons of value and already makes the built-in server much more
scalable. But I don't want to stop there.
The existing server-side caching implementation has a big weakness:
it requires the server to send data to the client. This means that
the Mercurial server is potentially sending gigabytes of data to
thousands of clients. This is problematic because compared to scaling
static file servers, scaling dynamic servers is *hard*.
A solution to this is to "offload" serving of content to something
that isn't the Mercurial server. By offloading content serving, you
turn the Mercurial server from a centralized monolithic service to
a distributed mostly-indexing service. Assuming high rates of content
offload, this should drastically reduce the total work performed by
the Mercurial server, both in terms of CPU and data transfer. This
will make Mercurial servers vastly easier to scale.
This commit defines the semantics for "content redirects" in wire
protocol version 2. Essentially:
* Servers advertise the set of locations a response could be served
from.
* When making requests, clients advertise the set of locations they
are willing to fetch content from.
* Servers can then replace the inline response with one that says
"get the response from over here instead."
This feature - when fully implemented - will allow extending the
server-side caching layer to facilitate such things as integrating
your server-side cache with a scalable blob store (such as S3 or
a CDN) and offloading most data transfer to that external service.
This feature could also be leveraged for load balancing. e.g.
requests could come into a central server and then get redirected
to an available mirror depending on server availability or locality.
There's tons of potential :)
Differential Revision: https://phab.mercurial-scm.org/D4774
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 26 Sep 2018 18:02:06 -0700 |
parents | 617ae7e33a65 |
children | 47ef023d0165 |
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#!/usr/bin/env python # # hggettext - carefully extract docstrings for Mercurial # # Copyright 2009 Matt Mackall <mpm@selenic.com> and others # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. # The normalize function is taken from pygettext which is distributed # with Python under the Python License, which is GPL compatible. """Extract docstrings from Mercurial commands. Compared to pygettext, this script knows about the cmdtable and table dictionaries used by Mercurial, and will only extract docstrings from functions mentioned therein. Use xgettext like normal to extract strings marked as translatable and join the message cataloges to get the final catalog. """ from __future__ import absolute_import, print_function import inspect import os import re import sys def escape(s): # The order is important, the backslash must be escaped first # since the other replacements introduce new backslashes # themselves. s = s.replace('\\', '\\\\') s = s.replace('\n', '\\n') s = s.replace('\r', '\\r') s = s.replace('\t', '\\t') s = s.replace('"', '\\"') return s def normalize(s): # This converts the various Python string types into a format that # is appropriate for .po files, namely much closer to C style. lines = s.split('\n') if len(lines) == 1: s = '"' + escape(s) + '"' else: if not lines[-1]: del lines[-1] lines[-1] = lines[-1] + '\n' lines = map(escape, lines) lineterm = '\\n"\n"' s = '""\n"' + lineterm.join(lines) + '"' return s def poentry(path, lineno, s): return ('#: %s:%d\n' % (path, lineno) + 'msgid %s\n' % normalize(s) + 'msgstr ""\n') doctestre = re.compile(r'^ +>>> ', re.MULTILINE) def offset(src, doc, name, lineno, default): """Compute offset or issue a warning on stdout.""" # remove doctest part, in order to avoid backslash mismatching m = doctestre.search(doc) if m: doc = doc[:m.start()] # Backslashes in doc appear doubled in src. end = src.find(doc.replace('\\', '\\\\')) if end == -1: # This can happen if the docstring contains unnecessary escape # sequences such as \" in a triple-quoted string. The problem # is that \" is turned into " and so doc wont appear in src. sys.stderr.write("%s:%d:warning:" " unknown docstr offset, assuming %d lines\n" % (name, lineno, default)) return default else: return src.count('\n', 0, end) def importpath(path): """Import a path like foo/bar/baz.py and return the baz module.""" if path.endswith('.py'): path = path[:-3] if path.endswith('/__init__'): path = path[:-9] path = path.replace('/', '.') mod = __import__(path) for comp in path.split('.')[1:]: mod = getattr(mod, comp) return mod def docstrings(path): """Extract docstrings from path. This respects the Mercurial cmdtable/table convention and will only extract docstrings from functions mentioned in these tables. """ mod = importpath(path) if not path.startswith('mercurial/') and mod.__doc__: with open(path) as fobj: src = fobj.read() lineno = 1 + offset(src, mod.__doc__, path, 1, 7) print(poentry(path, lineno, mod.__doc__)) functions = list(getattr(mod, 'i18nfunctions', [])) functions = [(f, True) for f in functions] cmdtable = getattr(mod, 'cmdtable', {}) if not cmdtable: # Maybe we are processing mercurial.commands? cmdtable = getattr(mod, 'table', {}) functions.extend((c[0], False) for c in cmdtable.itervalues()) for func, rstrip in functions: if func.__doc__: docobj = func # this might be a proxy to provide formatted doc func = getattr(func, '_origfunc', func) funcmod = inspect.getmodule(func) extra = '' if funcmod.__package__ == funcmod.__name__: extra = '/__init__' actualpath = '%s%s.py' % (funcmod.__name__.replace('.', '/'), extra) src = inspect.getsource(func) lineno = inspect.getsourcelines(func)[1] doc = docobj.__doc__ origdoc = getattr(docobj, '_origdoc', '') if rstrip: doc = doc.rstrip() origdoc = origdoc.rstrip() if origdoc: lineno += offset(src, origdoc, actualpath, lineno, 1) else: lineno += offset(src, doc, actualpath, lineno, 1) print(poentry(actualpath, lineno, doc)) def rawtext(path): with open(path) as f: src = f.read() print(poentry(path, 1, src)) if __name__ == "__main__": # It is very important that we import the Mercurial modules from # the source tree where hggettext is executed. Otherwise we might # accidentally import and extract strings from a Mercurial # installation mentioned in PYTHONPATH. sys.path.insert(0, os.getcwd()) from mercurial import demandimport; demandimport.enable() for path in sys.argv[1:]: if path.endswith('.txt'): rawtext(path) else: docstrings(path)