view tests/test-batching.py @ 37533:df4985497986

wireproto: implement capabilities for wire protocol v2

The capabilities mechanism for wire protocol version 2 represents a
clean break from version 1.

Instead of effectively exchanging a set of capabilities, we're
exchanging a rich data structure.

This data structure currently contains information about
every available command, including its accepted arguments. It also
contains information about supported compression formats.

Exposing information about supported commands will allow clients
to automatically generate bindings to the server. Clients will be
able to do things like detect when they are attempting to run a
command that isn't known to the server. Exposing the required
permissions to run a command can be used by clients to determine if
they have privileges to call a command before actually calling it.
We could potentially even have clients send credentials
preemptively without waiting for the server to deny the command
request. Lots of potential here.

The data returned by this command will likely evolve heavily. So we
shouldn't bikeshed the implementation just yet.

Differential Revision: https://phab.mercurial-scm.org/D3200

# test-batching.py - tests for transparent command batching
#
# Copyright 2011 Peter Arrenbrecht <[e-mail]>
#
# 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 (
    error,
    peer,
    util,
    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 batchiter(self):
        '''Support for local batching.'''
        return peer.localiterbatcher(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 proxied methods.
    batch = it.batchiter()
    # The calls return futures to eventually hold results.
    foo = batch.foo(one="One", two="Two")
    bar = batch.bar("Eins", "Zwei")
    bar2 = batch.bar(b="Uno", a="Due")

    # Future shouldn't be set until we submit().
    assert isinstance(foo, peer.future)
    assert not util.safehasattr(foo, 'value')
    assert not util.safehasattr(bar, 'value')
    batch.submit()
    # Call results() to obtain results as a generator.
    results = batch.results()

    # Future results shouldn't be set until we consume a value.
    assert not util.safehasattr(foo, 'value')
    foovalue = next(results)
    assert util.safehasattr(foo, 'value')
    assert foovalue == foo.value
    print(foo.value)
    next(results)
    print(bar.value)
    next(results)
    print(bar2.value)

    # We should be at the end of the results generator.
    try:
        next(results)
    except StopIteration:
        print('proper end of results generator')
    else:
        print('extra emitted element!')

    # Attempting to call a non-batchable method inside a batch fails.
    batch = it.batchiter()
    try:
        batch.greet(name='John Smith')
    except error.ProgrammingError as e:
        print(e)

    # Attempting to call a local method inside a batch fails.
    batch = it.batchiter()
    try:
        batch.hello()
    except error.ProgrammingError as e:
        print(e)

# 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,)])
        for r in res.split(';'):
            yield r

    def batchiter(self):
        return wireproto.remoteiterbatcher(self)

    @peer.batchable
    def foo(self, one, two=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)