view tests/test-verify-repo-operations.py @ 40021:c537144fdbef

wireprotov2: support response caching

One of the things I've learned from managing VCS servers over the
years is that they are hard to scale. It is well known that some
companies have very beefy (read: very expensive) servers to power
their VCS needs. It is also known that specialized servers for
various VCS exist in order to facilitate scaling servers. (Mercurial
is in this boat.)

One of the aspects that make a VCS server hard to scale is the
high CPU load incurred by constant client clone/pull operations.

To alleviate the scaling pain associated with data retrieval
operations, I want to integrate caching into the Mercurial wire
protocol server as robustly as possible such that servers can
aggressively cache responses and defer as much server load as
possible.

This commit represents the initial implementation of a general
caching layer in wire protocol version 2.

We define a new interface and behavior for a wire protocol cacher
in repository.py. (This is probably where a reviewer should look
first to understand what is going on.)

The bulk of the added code is in wireprotov2server.py, where we
define how a command can opt in to being cached and integrate
caching into command dispatching.

From a very high-level:

* A command can declare itself as cacheable by providing a callable
  that can be used to derive a cache key.
* At dispatch time, if a command is cacheable, we attempt to
  construct a cacher and use it for serving the request and/or
  caching the request.
* The dispatch layer handles the bulk of the business logic for
  caching, making cachers mostly "dumb content stores."
* The mechanism for invalidating cached entries (one of the harder
  parts about caching in general) is by varying the cache key when
  state changes. As such, cachers don't need to be concerned with
  cache invalidation.

Initially, we've hooked up support for caching "manifestdata" and
"filedata" commands. These are the simplest to cache, as they should
be immutable over time. Caching of commands related to changeset
data is a bit harder (because cache validation is impacted by
changes to bookmarks, phases, etc). This will be implemented later.
(Strictly speaking, censoring a file should invalidate caches. I've
added an inline TODO to track this edge case.)

To prove it works, this commit implements a test-only extension
providing in-memory caching backed by an lrucachedict. A new test
showing this extension behaving properly is added. FWIW, the
cacher is ~50 lines of code, demonstrating the relative ease with
which a cache can be added to a server.

While the test cacher is not suitable for production workloads, just
for kicks I performed a clone of just the changeset and manifest data
for the mozilla-unified repository. With a fully warmed cache (of just
the manifest data since changeset data is not cached), server-side
CPU usage dropped from ~73s to ~28s. That's pretty significant and
demonstrates the potential that response caching has on server
scalability!

Differential Revision: https://phab.mercurial-scm.org/D4773

from __future__ import print_function, absolute_import

"""Fuzz testing for operations against a Mercurial repository

This uses Hypothesis's stateful testing to generate random repository
operations and test Mercurial using them, both to see if there are any
unexpected errors and to compare different versions of it."""

import os
import subprocess
import sys

# Only run if slow tests are allowed
if subprocess.call(['python', '%s/hghave' % os.environ['TESTDIR'],
                    'slow']):
    sys.exit(80)

# These tests require Hypothesis and pytz to be installed.
# Running 'pip install hypothesis pytz' will achieve that.
# Note: This won't work if you're running Python < 2.7.
try:
    from hypothesis.extra.datetime import datetimes
except ImportError:
    sys.stderr.write("skipped: hypothesis or pytz not installed" + os.linesep)
    sys.exit(80)

# If you are running an old version of pip you may find that the enum34
# backport is not installed automatically. If so 'pip install enum34' will
# fix this problem.
try:
    import enum
    assert enum  # Silence pyflakes
except ImportError:
    sys.stderr.write("skipped: enum34 not installed" + os.linesep)
    sys.exit(80)

import binascii
from contextlib import contextmanager
import errno
import pipes
import shutil
import silenttestrunner
import subprocess

from hypothesis.errors import HypothesisException
from hypothesis.stateful import (
    rule, RuleBasedStateMachine, Bundle, precondition)
from hypothesis import settings, note, strategies as st
from hypothesis.configuration import set_hypothesis_home_dir
from hypothesis.database import ExampleDatabase

testdir = os.path.abspath(os.environ["TESTDIR"])

# We store Hypothesis examples here rather in the temporary test directory
# so that when rerunning a failing test this always results in refinding the
# previous failure. This directory is in .hgignore and should not be checked in
# but is useful to have for development.
set_hypothesis_home_dir(os.path.join(testdir, ".hypothesis"))

runtests = os.path.join(os.environ["RUNTESTDIR"], "run-tests.py")
testtmp = os.environ["TESTTMP"]
assert os.path.isdir(testtmp)

generatedtests = os.path.join(testdir, "hypothesis-generated")

try:
    os.makedirs(generatedtests)
except OSError:
    pass

# We write out generated .t files to a file in order to ease debugging and to
# give a starting point for turning failures Hypothesis finds into normal
# tests. In order to ensure that multiple copies of this test can be run in
# parallel we use atomic file create to ensure that we always get a unique
# name.
file_index = 0
while True:
    file_index += 1
    savefile = os.path.join(generatedtests, "test-generated-%d.t" % (
        file_index,
    ))
    try:
        os.close(os.open(savefile, os.O_CREAT | os.O_EXCL | os.O_WRONLY))
        break
    except OSError as e:
        if e.errno != errno.EEXIST:
            raise
assert os.path.exists(savefile)

hgrc = os.path.join(".hg", "hgrc")

filecharacters = (
    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
    "[]^_`;=@{}~ !#$%&'()+,-"
)

files = st.text(filecharacters, min_size=1).map(lambda x: x.strip()).filter(
    bool).map(lambda s: s.encode('ascii'))

safetext = st.text(st.characters(
    min_codepoint=1, max_codepoint=127,
    blacklist_categories=('Cc', 'Cs')), min_size=1).map(
    lambda s: s.encode('utf-8')
)

extensions = st.sampled_from(('shelve', 'mq', 'blackbox',))

@contextmanager
def acceptableerrors(*args):
    """Sometimes we know an operation we're about to perform might fail, and
    we're OK with some of the failures. In those cases this may be used as a
    context manager and will swallow expected failures, as identified by
    substrings of the error message Mercurial emits."""
    try:
        yield
    except subprocess.CalledProcessError as e:
        if not any(a in e.output for a in args):
            note(e.output)
            raise

reponames = st.text("abcdefghijklmnopqrstuvwxyz01234556789", min_size=1).map(
    lambda s: s.encode('ascii')
)

class verifyingstatemachine(RuleBasedStateMachine):
    """This defines the set of acceptable operations on a Mercurial repository
    using Hypothesis's RuleBasedStateMachine.

    The general concept is that we manage multiple repositories inside a
    repos/ directory in our temporary test location. Some of these are freshly
    inited, some are clones of the others. Our current working directory is
    always inside one of these repositories while the tests are running.

    Hypothesis then performs a series of operations against these repositories,
    including hg commands, generating contents and editing the .hgrc file.
    If these operations fail in unexpected ways or behave differently in
    different configurations of Mercurial, the test will fail and a minimized
    .t test file will be written to the hypothesis-generated directory to
    exhibit that failure.

    Operations are defined as methods with @rule() decorators. See the
    Hypothesis documentation at
    http://hypothesis.readthedocs.org/en/release/stateful.html for more
    details."""

    # A bundle is a reusable collection of previously generated data which may
    # be provided as arguments to future operations.
    repos = Bundle('repos')
    paths = Bundle('paths')
    contents = Bundle('contents')
    branches = Bundle('branches')
    committimes = Bundle('committimes')

    def __init__(self):
        super(verifyingstatemachine, self).__init__()
        self.repodir = os.path.join(testtmp, "repos")
        if os.path.exists(self.repodir):
            shutil.rmtree(self.repodir)
        os.chdir(testtmp)
        self.log = []
        self.failed = False
        self.configperrepo = {}
        self.all_extensions = set()
        self.non_skippable_extensions = set()

        self.mkdirp("repos")
        self.cd("repos")
        self.mkdirp("repo1")
        self.cd("repo1")
        self.hg("init")

    def teardown(self):
        """On teardown we clean up after ourselves as usual, but we also
        do some additional testing: We generate a .t file based on our test
        run using run-test.py -i to get the correct output.

        We then test it in a number of other configurations, verifying that
        each passes the same test."""
        super(verifyingstatemachine, self).teardown()
        try:
            shutil.rmtree(self.repodir)
        except OSError:
            pass
        ttest = os.linesep.join("  " + l for l in self.log)
        os.chdir(testtmp)
        path = os.path.join(testtmp, "test-generated.t")
        with open(path, 'w') as o:
            o.write(ttest + os.linesep)
        with open(os.devnull, "w") as devnull:
            rewriter = subprocess.Popen(
                [runtests, "--local", "-i", path], stdin=subprocess.PIPE,
                stdout=devnull, stderr=devnull,
            )
            rewriter.communicate("yes")
            with open(path, 'r') as i:
                ttest = i.read()

        e = None
        if not self.failed:
            try:
                output = subprocess.check_output([
                    runtests, path, "--local", "--pure"
                ], stderr=subprocess.STDOUT)
                assert "Ran 1 test" in output, output
                for ext in (
                    self.all_extensions - self.non_skippable_extensions
                ):
                    tf = os.path.join(testtmp, "test-generated-no-%s.t" % (
                        ext,
                    ))
                    with open(tf, 'w') as o:
                        for l in ttest.splitlines():
                            if l.startswith("  $ hg"):
                                l = l.replace(
                                    "--config %s=" % (
                                        extensionconfigkey(ext),), "")
                            o.write(l + os.linesep)
                    with open(tf, 'r') as r:
                        t = r.read()
                        assert ext not in t, t
                    output = subprocess.check_output([
                        runtests, tf, "--local",
                    ], stderr=subprocess.STDOUT)
                    assert "Ran 1 test" in output, output
            except subprocess.CalledProcessError as e:
                note(e.output)
        if self.failed or e is not None:
            with open(savefile, "wb") as o:
                o.write(ttest)
        if e is not None:
            raise e

    def execute_step(self, step):
        try:
            return super(verifyingstatemachine, self).execute_step(step)
        except (HypothesisException, KeyboardInterrupt):
            raise
        except Exception:
            self.failed = True
            raise

    # Section: Basic commands.
    def mkdirp(self, path):
        if os.path.exists(path):
            return
        self.log.append(
            "$ mkdir -p -- %s" % (pipes.quote(os.path.relpath(path)),))
        os.makedirs(path)

    def cd(self, path):
        path = os.path.relpath(path)
        if path == ".":
            return
        os.chdir(path)
        self.log.append("$ cd -- %s" % (pipes.quote(path),))

    def hg(self, *args):
        extra_flags = []
        for key, value in self.config.items():
            extra_flags.append("--config")
            extra_flags.append("%s=%s" % (key, value))
        self.command("hg", *(tuple(extra_flags) + args))

    def command(self, *args):
        self.log.append("$ " + ' '.join(map(pipes.quote, args)))
        subprocess.check_output(args, stderr=subprocess.STDOUT)

    # Section: Set up basic data
    # This section has no side effects but generates data that we will want
    # to use later.
    @rule(
        target=paths,
        source=st.lists(files, min_size=1).map(lambda l: os.path.join(*l)))
    def genpath(self, source):
        return source

    @rule(
        target=committimes,
        when=datetimes(min_year=1970, max_year=2038) | st.none())
    def gentime(self, when):
        return when

    @rule(
        target=contents,
        content=st.one_of(
            st.binary(),
            st.text().map(lambda x: x.encode('utf-8'))
        ))
    def gencontent(self, content):
        return content

    @rule(
        target=branches,
        name=safetext,
    )
    def genbranch(self, name):
        return name

    @rule(target=paths, source=paths)
    def lowerpath(self, source):
        return source.lower()

    @rule(target=paths, source=paths)
    def upperpath(self, source):
        return source.upper()

    # Section: Basic path operations
    @rule(path=paths, content=contents)
    def writecontent(self, path, content):
        self.unadded_changes = True
        if os.path.isdir(path):
            return
        parent = os.path.dirname(path)
        if parent:
            try:
                self.mkdirp(parent)
            except OSError:
                # It may be the case that there is a regular file that has
                # previously been created that has the same name as an ancestor
                # of the current path. This will cause mkdirp to fail with this
                # error. We just turn this into a no-op in that case.
                return
        with open(path, 'wb') as o:
            o.write(content)
        self.log.append((
            "$ python -c 'import binascii; "
            "print(binascii.unhexlify(\"%s\"))' > %s") % (
                binascii.hexlify(content),
                pipes.quote(path),
            ))

    @rule(path=paths)
    def addpath(self, path):
        if os.path.exists(path):
            self.hg("add", "--", path)

    @rule(path=paths)
    def forgetpath(self, path):
        if os.path.exists(path):
            with acceptableerrors(
                "file is already untracked",
            ):
                self.hg("forget", "--", path)

    @rule(s=st.none() | st.integers(0, 100))
    def addremove(self, s):
        args = ["addremove"]
        if s is not None:
            args.extend(["-s", str(s)])
        self.hg(*args)

    @rule(path=paths)
    def removepath(self, path):
        if os.path.exists(path):
            with acceptableerrors(
                'file is untracked',
                'file has been marked for add',
                'file is modified',
            ):
                self.hg("remove", "--", path)

    @rule(
        message=safetext,
        amend=st.booleans(),
        when=committimes,
        addremove=st.booleans(),
        secret=st.booleans(),
        close_branch=st.booleans(),
    )
    def maybecommit(
        self, message, amend, when, addremove, secret, close_branch
    ):
        command = ["commit"]
        errors = ["nothing changed"]
        if amend:
            errors.append("cannot amend public changesets")
            command.append("--amend")
        command.append("-m" + pipes.quote(message))
        if secret:
            command.append("--secret")
        if close_branch:
            command.append("--close-branch")
            errors.append("can only close branch heads")
        if addremove:
            command.append("--addremove")
        if when is not None:
            if when.year == 1970:
                errors.append('negative date value')
            if when.year == 2038:
                errors.append('exceeds 32 bits')
            command.append("--date=%s" % (
                when.strftime('%Y-%m-%d %H:%M:%S %z'),))

        with acceptableerrors(*errors):
            self.hg(*command)

    # Section: Repository management
    @property
    def currentrepo(self):
        return os.path.basename(os.getcwd())

    @property
    def config(self):
        return self.configperrepo.setdefault(self.currentrepo, {})

    @rule(
        target=repos,
        source=repos,
        name=reponames,
    )
    def clone(self, source, name):
        if not os.path.exists(os.path.join("..", name)):
            self.cd("..")
            self.hg("clone", source, name)
            self.cd(name)
        return name

    @rule(
        target=repos,
        name=reponames,
    )
    def fresh(self, name):
        if not os.path.exists(os.path.join("..", name)):
            self.cd("..")
            self.mkdirp(name)
            self.cd(name)
            self.hg("init")
        return name

    @rule(name=repos)
    def switch(self, name):
        self.cd(os.path.join("..", name))
        assert self.currentrepo == name
        assert os.path.exists(".hg")

    @rule(target=repos)
    def origin(self):
        return "repo1"

    @rule()
    def pull(self, repo=repos):
        with acceptableerrors(
            "repository default not found",
            "repository is unrelated",
        ):
            self.hg("pull")

    @rule(newbranch=st.booleans())
    def push(self, newbranch):
        with acceptableerrors(
            "default repository not configured",
            "no changes found",
        ):
            if newbranch:
                self.hg("push", "--new-branch")
            else:
                with acceptableerrors(
                    "creates new branches"
                ):
                    self.hg("push")

    # Section: Simple side effect free "check" operations
    @rule()
    def log(self):
        self.hg("log")

    @rule()
    def verify(self):
        self.hg("verify")

    @rule()
    def diff(self):
        self.hg("diff", "--nodates")

    @rule()
    def status(self):
        self.hg("status")

    @rule()
    def export(self):
        self.hg("export")

    # Section: Branch management
    @rule()
    def checkbranch(self):
        self.hg("branch")

    @rule(branch=branches)
    def switchbranch(self, branch):
        with acceptableerrors(
            'cannot use an integer as a name',
            'cannot be used in a name',
            'a branch of the same name already exists',
            'is reserved',
        ):
            self.hg("branch", "--", branch)

    @rule(branch=branches, clean=st.booleans())
    def update(self, branch, clean):
        with acceptableerrors(
            'unknown revision',
            'parse error',
        ):
            if clean:
                self.hg("update", "-C", "--", branch)
            else:
                self.hg("update", "--", branch)

    # Section: Extension management
    def hasextension(self, extension):
        return extensionconfigkey(extension) in self.config

    def commandused(self, extension):
        assert extension in self.all_extensions
        self.non_skippable_extensions.add(extension)

    @rule(extension=extensions)
    def addextension(self, extension):
        self.all_extensions.add(extension)
        self.config[extensionconfigkey(extension)] = ""

    @rule(extension=extensions)
    def removeextension(self, extension):
        self.config.pop(extensionconfigkey(extension), None)

    # Section: Commands from the shelve extension
    @rule()
    @precondition(lambda self: self.hasextension("shelve"))
    def shelve(self):
        self.commandused("shelve")
        with acceptableerrors("nothing changed"):
            self.hg("shelve")

    @rule()
    @precondition(lambda self: self.hasextension("shelve"))
    def unshelve(self):
        self.commandused("shelve")
        with acceptableerrors("no shelved changes to apply"):
            self.hg("unshelve")

class writeonlydatabase(ExampleDatabase):
    def __init__(self, underlying):
        super(ExampleDatabase, self).__init__()
        self.underlying = underlying

    def fetch(self, key):
        return ()

    def save(self, key, value):
        self.underlying.save(key, value)

    def delete(self, key, value):
        self.underlying.delete(key, value)

    def close(self):
        self.underlying.close()

def extensionconfigkey(extension):
    return "extensions." + extension

settings.register_profile(
    'default',  settings(
        timeout=300,
        stateful_step_count=50,
        max_examples=10,
    )
)

settings.register_profile(
    'fast',  settings(
        timeout=10,
        stateful_step_count=20,
        max_examples=5,
        min_satisfying_examples=1,
        max_shrinks=0,
    )
)

settings.register_profile(
    'continuous', settings(
        timeout=-1,
        stateful_step_count=1000,
        max_examples=10 ** 8,
        max_iterations=10 ** 8,
        database=writeonlydatabase(settings.default.database)
    )
)

settings.load_profile(os.getenv('HYPOTHESIS_PROFILE', 'default'))

verifyingtest = verifyingstatemachine.TestCase

verifyingtest.settings = settings.default

if __name__ == '__main__':
    try:
        silenttestrunner.main(__name__)
    finally:
        # So as to prevent proliferation of useless test files, if we never
        # actually wrote a failing test we clean up after ourselves and delete
        # the file for doing so that we owned.
        if os.path.exists(savefile) and os.path.getsize(savefile) == 0:
            os.unlink(savefile)