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httppeer: remove support for connecting to <0.9.1 servers (BC)...
httppeer: remove support for connecting to <0.9.1 servers (BC) Previously, HTTP wire protocol clients would attempt a "capabilities" wire protocol command. If that failed, they would fall back to issuing a "between" command. The "capabilities" command was added in Mercurial 0.9.1 (released July 2006). The "between" command has been present for as long as the wire protocol has existed. So if the "between" command failed, it was safe to assume that the remote could not speak any version of the Mercurial wire protocol. The "between" fallback was added in 395a84f78736 in 2011. Before that changeset, Mercurial would *always* issue the "between" command and would issue "capabilities" if capabilities were requested. At that time, many connections would issue "capabilities" eventually, so it was decided to issue "capabilities" by default and fall back to "between" if that failed. This saved a round trip when connecting to modern servers while still preserving compatibility with legacy servers. Fast forward ~7 years. Mercurial servers supporting "capabilities" have been around for over a decade. If modern clients are connecting to <0.9.1 servers, they are getting a bad experience. They may even be getting bad data (an old server is vulnerable to numerous security issues and could have been p0wned, leading to a Mercurial repository serving backdoors or other badness). In addition, the fallback can harm experience for modern servers. If a client experiences an intermittent HTTP request failure (due to bad network, etc) and falls back to a "between" that works, it would assume an empty capability set and would attempt to communicate with the repository using a very ancient wire protocol. Auditing HTTP logs for hg.mozilla.org, I did find a handful of requests for the null range of the "between" command. However, requests can be days apart. And when I do see requests, they come in batches. Those batches seem to correlate to spikes of HTTP 500 or other server/network events. So I think these requests are fallbacks from failed "capabilities" requests and not from old clients. If you need even more evidence to discontinue support, apparently we have no test coverage for communicating with servers not supporting "capabilities." I know this because all tests pass with the "between" fallback removed. Finally, server-side support for <0.9.1 pushing (the "addchangegroup" wire protocol command along with locking-related commands) was dropped from the HTTP client in fda0867cfe03 in 2017 and the SSH client in 9f6e0e7ef828 in 2015. I think this all adds up to enough justification for removing client support for communicating with servers not supporting "capabilities." So this commit removes that fallback. Differential Revision: https://phab.mercurial-scm.org/D2001

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dagparser.py
488 lines | 14.7 KiB | text/x-python | PythonLexer
# dagparser.py - parser and generator for concise description of DAGs
#
# Copyright 2010 Peter Arrenbrecht <peter@arrenbrecht.ch>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
import re
import string
from .i18n import _
from . import (
error,
pycompat,
util,
)
def parsedag(desc):
'''parses a DAG from a concise textual description; generates events
"+n" is a linear run of n nodes based on the current default parent
"." is a single node based on the current default parent
"$" resets the default parent to -1 (implied at the start);
otherwise the default parent is always the last node created
"<p" sets the default parent to the backref p
"*p" is a fork at parent p, where p is a backref
"*p1/p2/.../pn" is a merge of parents p1..pn, where the pi are backrefs
"/p2/.../pn" is a merge of the preceding node and p2..pn
":name" defines a label for the preceding node; labels can be redefined
"@text" emits an annotation event for text
"!command" emits an action event for the current node
"!!my command\n" is like "!", but to the end of the line
"#...\n" is a comment up to the end of the line
Whitespace between the above elements is ignored.
A backref is either
* a number n, which references the node curr-n, where curr is the current
node, or
* the name of a label you placed earlier using ":name", or
* empty to denote the default parent.
All string valued-elements are either strictly alphanumeric, or must
be enclosed in double quotes ("..."), with "\" as escape character.
Generates sequence of
('n', (id, [parentids])) for node creation
('l', (id, labelname)) for labels on nodes
('a', text) for annotations
('c', command) for actions (!)
('C', command) for line actions (!!)
Examples
--------
Example of a complex graph (output not shown for brevity):
>>> len(list(parsedag(b"""
...
... +3 # 3 nodes in linear run
... :forkhere # a label for the last of the 3 nodes from above
... +5 # 5 more nodes on one branch
... :mergethis # label again
... <forkhere # set default parent to labeled fork node
... +10 # 10 more nodes on a parallel branch
... @stable # following nodes will be annotated as "stable"
... +5 # 5 nodes in stable
... !addfile # custom command; could trigger new file in next node
... +2 # two more nodes
... /mergethis # merge last node with labeled node
... +4 # 4 more nodes descending from merge node
...
... """)))
34
Empty list:
>>> list(parsedag(b""))
[]
A simple linear run:
>>> list(parsedag(b"+3"))
[('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]
Some non-standard ways to define such runs:
>>> list(parsedag(b"+1+2"))
[('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]
>>> list(parsedag(b"+1*1*"))
[('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]
>>> list(parsedag(b"*"))
[('n', (0, [-1]))]
>>> list(parsedag(b"..."))
[('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]
A fork and a join, using numeric back references:
>>> list(parsedag(b"+2*2*/2"))
[('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [0])), ('n', (3, [2, 1]))]
>>> list(parsedag(b"+2<2+1/2"))
[('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [0])), ('n', (3, [2, 1]))]
Placing a label:
>>> list(parsedag(b"+1 :mylabel +1"))
[('n', (0, [-1])), ('l', (0, 'mylabel')), ('n', (1, [0]))]
An empty label (silly, really):
>>> list(parsedag(b"+1:+1"))
[('n', (0, [-1])), ('l', (0, '')), ('n', (1, [0]))]
Fork and join, but with labels instead of numeric back references:
>>> list(parsedag(b"+1:f +1:p2 *f */p2"))
[('n', (0, [-1])), ('l', (0, 'f')), ('n', (1, [0])), ('l', (1, 'p2')),
('n', (2, [0])), ('n', (3, [2, 1]))]
>>> list(parsedag(b"+1:f +1:p2 <f +1 /p2"))
[('n', (0, [-1])), ('l', (0, 'f')), ('n', (1, [0])), ('l', (1, 'p2')),
('n', (2, [0])), ('n', (3, [2, 1]))]
Restarting from the root:
>>> list(parsedag(b"+1 $ +1"))
[('n', (0, [-1])), ('n', (1, [-1]))]
Annotations, which are meant to introduce sticky state for subsequent nodes:
>>> list(parsedag(b"+1 @ann +1"))
[('n', (0, [-1])), ('a', 'ann'), ('n', (1, [0]))]
>>> list(parsedag(b'+1 @"my annotation" +1'))
[('n', (0, [-1])), ('a', 'my annotation'), ('n', (1, [0]))]
Commands, which are meant to operate on the most recently created node:
>>> list(parsedag(b"+1 !cmd +1"))
[('n', (0, [-1])), ('c', 'cmd'), ('n', (1, [0]))]
>>> list(parsedag(b'+1 !"my command" +1'))
[('n', (0, [-1])), ('c', 'my command'), ('n', (1, [0]))]
>>> list(parsedag(b'+1 !!my command line\\n +1'))
[('n', (0, [-1])), ('C', 'my command line'), ('n', (1, [0]))]
Comments, which extend to the end of the line:
>>> list(parsedag(b'+1 # comment\\n+1'))
[('n', (0, [-1])), ('n', (1, [0]))]
Error:
>>> try: list(parsedag(b'+1 bad'))
... except Exception as e: print(pycompat.sysstr(bytes(e)))
invalid character in dag description: bad...
'''
if not desc:
return
wordchars = pycompat.bytestr(string.ascii_letters + string.digits)
labels = {}
p1 = -1
r = 0
def resolve(ref):
if not ref:
return p1
elif ref[0] in pycompat.bytestr(string.digits):
return r - int(ref)
else:
return labels[ref]
chiter = pycompat.iterbytestr(desc)
def nextch():
return next(chiter, '\0')
def nextrun(c, allow):
s = ''
while c in allow:
s += c
c = nextch()
return c, s
def nextdelimited(c, limit, escape):
s = ''
while c != limit:
if c == escape:
c = nextch()
s += c
c = nextch()
return nextch(), s
def nextstring(c):
if c == '"':
return nextdelimited(nextch(), '"', '\\')
else:
return nextrun(c, wordchars)
c = nextch()
while c != '\0':
while c in pycompat.bytestr(string.whitespace):
c = nextch()
if c == '.':
yield 'n', (r, [p1])
p1 = r
r += 1
c = nextch()
elif c == '+':
c, digs = nextrun(nextch(), pycompat.bytestr(string.digits))
n = int(digs)
for i in xrange(0, n):
yield 'n', (r, [p1])
p1 = r
r += 1
elif c in '*/':
if c == '*':
c = nextch()
c, pref = nextstring(c)
prefs = [pref]
while c == '/':
c, pref = nextstring(nextch())
prefs.append(pref)
ps = [resolve(ref) for ref in prefs]
yield 'n', (r, ps)
p1 = r
r += 1
elif c == '<':
c, ref = nextstring(nextch())
p1 = resolve(ref)
elif c == ':':
c, name = nextstring(nextch())
labels[name] = p1
yield 'l', (p1, name)
elif c == '@':
c, text = nextstring(nextch())
yield 'a', text
elif c == '!':
c = nextch()
if c == '!':
cmd = ''
c = nextch()
while c not in '\n\r\0':
cmd += c
c = nextch()
yield 'C', cmd
else:
c, cmd = nextstring(c)
yield 'c', cmd
elif c == '#':
while c not in '\n\r\0':
c = nextch()
elif c == '$':
p1 = -1
c = nextch()
elif c == '\0':
return # in case it was preceded by whitespace
else:
s = ''
i = 0
while c != '\0' and i < 10:
s += c
i += 1
c = nextch()
raise error.Abort(_('invalid character in dag description: '
'%s...') % s)
def dagtextlines(events,
addspaces=True,
wraplabels=False,
wrapannotations=False,
wrapcommands=False,
wrapnonlinear=False,
usedots=False,
maxlinewidth=70):
'''generates single lines for dagtext()'''
def wrapstring(text):
if re.match("^[0-9a-z]*$", text):
return text
return '"' + text.replace('\\', '\\\\').replace('"', '\"') + '"'
def gen():
labels = {}
run = 0
wantr = 0
needroot = False
for kind, data in events:
if kind == 'n':
r, ps = data
# sanity check
if r != wantr:
raise error.Abort(_("expected id %i, got %i") % (wantr, r))
if not ps:
ps = [-1]
else:
for p in ps:
if p >= r:
raise error.Abort(_("parent id %i is larger than "
"current id %i") % (p, r))
wantr += 1
# new root?
p1 = r - 1
if len(ps) == 1 and ps[0] == -1:
if needroot:
if run:
yield '+%d' % run
run = 0
if wrapnonlinear:
yield '\n'
yield '$'
p1 = -1
else:
needroot = True
if len(ps) == 1 and ps[0] == p1:
if usedots:
yield "."
else:
run += 1
else:
if run:
yield '+%d' % run
run = 0
if wrapnonlinear:
yield '\n'
prefs = []
for p in ps:
if p == p1:
prefs.append('')
elif p in labels:
prefs.append(labels[p])
else:
prefs.append('%d' % (r - p))
yield '*' + '/'.join(prefs)
else:
if run:
yield '+%d' % run
run = 0
if kind == 'l':
rid, name = data
labels[rid] = name
yield ':' + name
if wraplabels:
yield '\n'
elif kind == 'c':
yield '!' + wrapstring(data)
if wrapcommands:
yield '\n'
elif kind == 'C':
yield '!!' + data
yield '\n'
elif kind == 'a':
if wrapannotations:
yield '\n'
yield '@' + wrapstring(data)
elif kind == '#':
yield '#' + data
yield '\n'
else:
raise error.Abort(_("invalid event type in dag: "
"('%s', '%s')")
% (util.escapestr(kind),
util.escapestr(data)))
if run:
yield '+%d' % run
line = ''
for part in gen():
if part == '\n':
if line:
yield line
line = ''
else:
if len(line) + len(part) >= maxlinewidth:
yield line
line = ''
elif addspaces and line and part != '.':
line += ' '
line += part
if line:
yield line
def dagtext(dag,
addspaces=True,
wraplabels=False,
wrapannotations=False,
wrapcommands=False,
wrapnonlinear=False,
usedots=False,
maxlinewidth=70):
'''generates lines of a textual representation for a dag event stream
events should generate what parsedag() does, so:
('n', (id, [parentids])) for node creation
('l', (id, labelname)) for labels on nodes
('a', text) for annotations
('c', text) for commands
('C', text) for line commands ('!!')
('#', text) for comment lines
Parent nodes must come before child nodes.
Examples
--------
Linear run:
>>> dagtext([(b'n', (0, [-1])), (b'n', (1, [0]))])
'+2'
Two roots:
>>> dagtext([(b'n', (0, [-1])), (b'n', (1, [-1]))])
'+1 $ +1'
Fork and join:
>>> dagtext([(b'n', (0, [-1])), (b'n', (1, [0])), (b'n', (2, [0])),
... (b'n', (3, [2, 1]))])
'+2 *2 */2'
Fork and join with labels:
>>> dagtext([(b'n', (0, [-1])), (b'l', (0, b'f')), (b'n', (1, [0])),
... (b'l', (1, b'p2')), (b'n', (2, [0])), (b'n', (3, [2, 1]))])
'+1 :f +1 :p2 *f */p2'
Annotations:
>>> dagtext([(b'n', (0, [-1])), (b'a', b'ann'), (b'n', (1, [0]))])
'+1 @ann +1'
>>> dagtext([(b'n', (0, [-1])),
... (b'a', b'my annotation'),
... (b'n', (1, [0]))])
'+1 @"my annotation" +1'
Commands:
>>> dagtext([(b'n', (0, [-1])), (b'c', b'cmd'), (b'n', (1, [0]))])
'+1 !cmd +1'
>>> dagtext([(b'n', (0, [-1])),
... (b'c', b'my command'),
... (b'n', (1, [0]))])
'+1 !"my command" +1'
>>> dagtext([(b'n', (0, [-1])),
... (b'C', b'my command line'),
... (b'n', (1, [0]))])
'+1 !!my command line\\n+1'
Comments:
>>> dagtext([(b'n', (0, [-1])), (b'#', b' comment'), (b'n', (1, [0]))])
'+1 # comment\\n+1'
>>> dagtext([])
''
Combining parsedag and dagtext:
>>> dagtext(parsedag(b'+1 :f +1 :p2 *f */p2'))
'+1 :f +1 :p2 *f */p2'
'''
return "\n".join(dagtextlines(dag,
addspaces,
wraplabels,
wrapannotations,
wrapcommands,
wrapnonlinear,
usedots,
maxlinewidth))