Mercurial > hg
view tests/test-batching.py @ 32697:19b9fc40cc51
revlog: skeleton support for version 2 revlogs
There are a number of improvements we want to make to revlogs
that will require a new version - version 2. It is unclear what the
full set of improvements will be or when we'll be done with them.
What I do know is that the process will likely take longer than a
single release, will require input from various stakeholders to
evaluate changes, and will have many contentious debates and
bikeshedding.
It is unrealistic to develop revlog version 2 up front: there
are just too many uncertainties that we won't know until things
are implemented and experiments are run. Some changes will also
be invasive and prone to bit rot, so sitting on dozens of patches
is not practical.
This commit introduces skeleton support for version 2 revlogs in
a way that is flexible and not bound by backwards compatibility
concerns.
An experimental repo requirement for denoting revlog v2 has been
added. The requirement string has a sub-version component to it.
This will allow us to declare multiple requirements in the course
of developing revlog v2. Whenever we change the in-development
revlog v2 format, we can tweak the string, creating a new
requirement and locking out old clients. This will allow us to
make as many backwards incompatible changes and experiments to
revlog v2 as we want. In other words, we can land code and make
meaningful progress towards revlog v2 while still maintaining
extreme format flexibility up until the point we freeze the
format and remove the experimental labels.
To enable the new repo requirement, you must supply an experimental
and undocumented config option. But not just any boolean flag
will do: you need to explicitly use a value that no sane person
should ever type. This is an additional guard against enabling
revlog v2 on an installation it shouldn't be enabled on. The
specific scenario I'm trying to prevent is say a user with a
4.4 client with a frozen format enabling the option but then
downgrading to 4.3 and accidentally creating repos with an
outdated and unsupported repo format. Requiring a "challenge"
string should prevent this.
Because the format is not yet finalized and I don't want to take
any chances, revlog v2's version is currently 0xDEAD. I figure
squatting on a value we're likely never to use as an actual revlog
version to mean "internal testing only" is acceptable. And
"dead" is easily recognized as something meaningful.
There is a bunch of cleanup that is needed before work on revlog
v2 begins in earnest. I plan on doing that work once this patch
is accepted and we're comfortable with the idea of starting down
this path.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Fri, 19 May 2017 20:29:11 -0700 |
parents | 544908ae36ce |
children | e2fc2122029c |
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# test-batching.py - tests for transparent command batching # # Copyright 2011 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, print_function from mercurial import ( peer, wireproto, ) # equivalent of repo.repository class thing(object): def hello(self): return "Ready." # equivalent of localrepo.localrepository class localthing(thing): def foo(self, one, two=None): if one: return "%s and %s" % (one, two,) return "Nope" def bar(self, b, a): return "%s und %s" % (b, a,) def greet(self, name=None): return "Hello, %s" % name def batch(self): '''Support for local batching.''' return peer.localbatch(self) # usage of "thing" interface def use(it): # Direct call to base method shared between client and server. print(it.hello()) # Direct calls to proxied methods. They cause individual roundtrips. print(it.foo("Un", two="Deux")) print(it.bar("Eins", "Zwei")) # Batched call to a couple of (possibly proxied) methods. batch = it.batch() # The calls return futures to eventually hold results. foo = batch.foo(one="One", two="Two") foo2 = batch.foo(None) bar = batch.bar("Eins", "Zwei") # We can call non-batchable proxy methods, but the break the current batch # request and cause additional roundtrips. greet = batch.greet(name="John Smith") # We can also add local methods into the mix, but they break the batch too. hello = batch.hello() bar2 = batch.bar(b="Uno", a="Due") # Only now are all the calls executed in sequence, with as few roundtrips # as possible. batch.submit() # After the call to submit, the futures actually contain values. print(foo.value) print(foo2.value) print(bar.value) print(greet.value) print(hello.value) print(bar2.value) # local usage mylocal = localthing() print() print("== Local") use(mylocal) # demo remoting; mimicks what wireproto and HTTP/SSH do # shared def escapearg(plain): return (plain .replace(':', '::') .replace(',', ':,') .replace(';', ':;') .replace('=', ':=')) def unescapearg(escaped): return (escaped .replace(':=', '=') .replace(':;', ';') .replace(':,', ',') .replace('::', ':')) # server side # equivalent of wireproto's global functions class server(object): def __init__(self, local): self.local = local def _call(self, name, args): args = dict(arg.split('=', 1) for arg in args) return getattr(self, name)(**args) def perform(self, req): print("REQ:", req) name, args = req.split('?', 1) args = args.split('&') vals = dict(arg.split('=', 1) for arg in args) res = getattr(self, name)(**vals) print(" ->", res) return res def batch(self, cmds): res = [] for pair in cmds.split(';'): name, args = pair.split(':', 1) vals = {} for a in args.split(','): if a: n, v = a.split('=') vals[n] = unescapearg(v) res.append(escapearg(getattr(self, name)(**vals))) return ';'.join(res) def foo(self, one, two): return mangle(self.local.foo(unmangle(one), unmangle(two))) def bar(self, b, a): return mangle(self.local.bar(unmangle(b), unmangle(a))) def greet(self, name): return mangle(self.local.greet(unmangle(name))) myserver = server(mylocal) # local side # equivalent of wireproto.encode/decodelist, that is, type-specific marshalling # here we just transform the strings a bit to check we're properly en-/decoding def mangle(s): return ''.join(chr(ord(c) + 1) for c in s) def unmangle(s): return ''.join(chr(ord(c) - 1) for c in s) # equivalent of wireproto.wirerepository and something like http's wire format class remotething(thing): def __init__(self, server): self.server = server def _submitone(self, name, args): req = name + '?' + '&'.join(['%s=%s' % (n, v) for n, v in args]) return self.server.perform(req) def _submitbatch(self, cmds): req = [] for name, args in cmds: args = ','.join(n + '=' + escapearg(v) for n, v in args) req.append(name + ':' + args) req = ';'.join(req) res = self._submitone('batch', [('cmds', req,)]) return res.split(';') def batch(self): return wireproto.remotebatch(self) @peer.batchable def foo(self, one, two=None): if not one: yield "Nope", None encargs = [('one', mangle(one),), ('two', mangle(two),)] encresref = peer.future() yield encargs, encresref yield unmangle(encresref.value) @peer.batchable def bar(self, b, a): encresref = peer.future() yield [('b', mangle(b),), ('a', mangle(a),)], encresref yield unmangle(encresref.value) # greet is coded directly. It therefore does not support batching. If it # does appear in a batch, the batch is split around greet, and the call to # greet is done in its own roundtrip. def greet(self, name=None): return unmangle(self._submitone('greet', [('name', mangle(name),)])) # demo remote usage myproxy = remotething(myserver) print() print("== Remote") use(myproxy)