tests/wireprotosimplecache.py

strip: introduce a soft strip option

This is the first user-accessible way to use the archived phase introduced in
4.8. This implements a feature discussed during the Stockholm sprint, using
the archived phase for hiding changesets.

The archived phase behaves exactly as stripping: changesets are no longer
visible, but pulling/unbundling them will make then reappear. The only notable
difference is that unlike hard stripping, soft stripping does not affect
obsmarkers.

The next changeset will make use of the archived phase for history rewriting
command. However, having a way to manually trigger the feature first seems a
necessary step before exposing users to this phase; there is a way to
un-archived changesets (unbundling), so there must be a way to archive them
again.

Adding a flag to strip is a good way to provide access to the feature without
taking a too big risk on the final UI we want. The flag is experimental so it
won't be exposed by default.

Using the archived phase is faster and less traumatic for the repository than
actually stripping changesets.

# wireprotosimplecache.py - Extension providing in-memory wire protocol cache
#
# Copyright 2018 Gregory Szorc <[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

from mercurial import (
    extensions,
    registrar,
    repository,
    util,
    wireprotoserver,
    wireprototypes,
    wireprotov2server,
)
from mercurial.utils import (
    interfaceutil,
    stringutil,
)

CACHE = None

configtable = {}
configitem = registrar.configitem(configtable)

configitem(b'simplecache', b'cacheapi',
           default=False)
configitem(b'simplecache', b'cacheobjects',
           default=False)
configitem(b'simplecache', b'redirectsfile',
           default=None)

# API handler that makes cached keys available.
def handlecacherequest(rctx, req, res, checkperm, urlparts):
    if rctx.repo.ui.configbool(b'simplecache', b'cacheobjects'):
        res.status = b'500 Internal Server Error'
        res.setbodybytes(b'cacheobjects not supported for api server')
        return

    if not urlparts:
        res.status = b'200 OK'
        res.headers[b'Content-Type'] = b'text/plain'
        res.setbodybytes(b'simple cache server')
        return

    key = b'/'.join(urlparts)

    if key not in CACHE:
        res.status = b'404 Not Found'
        res.headers[b'Content-Type'] = b'text/plain'
        res.setbodybytes(b'key not found in cache')
        return

    res.status = b'200 OK'
    res.headers[b'Content-Type'] = b'application/mercurial-cbor'
    res.setbodybytes(CACHE[key])

def cachedescriptor(req, repo):
    return {}

wireprotoserver.API_HANDLERS[b'simplecache'] = {
    b'config': (b'simplecache', b'cacheapi'),
    b'handler': handlecacherequest,
    b'apidescriptor': cachedescriptor,
}

@interfaceutil.implementer(repository.iwireprotocolcommandcacher)
class memorycacher(object):
    def __init__(self, ui, command, encodefn, redirecttargets, redirecthashes,
                 req):
        self.ui = ui
        self.encodefn = encodefn
        self.redirecttargets = redirecttargets
        self.redirecthashes = redirecthashes
        self.req = req
        self.key = None
        self.cacheobjects = ui.configbool(b'simplecache', b'cacheobjects')
        self.cacheapi = ui.configbool(b'simplecache', b'cacheapi')
        self.buffered = []

        ui.log(b'simplecache', b'cacher constructed for %s\n', command)

    def __enter__(self):
        return self

    def __exit__(self, exctype, excvalue, exctb):
        if exctype:
            self.ui.log(b'simplecache', b'cacher exiting due to error\n')

    def adjustcachekeystate(self, state):
        # Needed in order to make tests deterministic. Don't copy this
        # pattern for production caches!
        del state[b'repo']

    def setcachekey(self, key):
        self.key = key
        return True

    def lookup(self):
        if self.key not in CACHE:
            self.ui.log(b'simplecache', b'cache miss for %s\n', self.key)
            return None

        entry = CACHE[self.key]
        self.ui.log(b'simplecache', b'cache hit for %s\n', self.key)

        redirectable = True

        if not self.cacheapi:
            redirectable = False
        elif not self.redirecttargets:
            redirectable = False
        else:
            clienttargets = set(self.redirecttargets)
            ourtargets = set(t[b'name'] for t in loadredirecttargets(self.ui))

            # We only ever redirect to a single target (for now). So we don't
            # need to store which target matched.
            if not clienttargets & ourtargets:
                redirectable = False

        if redirectable:
            paths = self.req.dispatchparts[:-3]
            paths.append(b'simplecache')
            paths.append(self.key)

            url = b'%s/%s' % (self.req.baseurl, b'/'.join(paths))

            #url = b'http://example.com/%s' % self.key
            self.ui.log(b'simplecache', b'sending content redirect for %s to '
                                        b'%s\n', self.key, url)
            response = wireprototypes.alternatelocationresponse(
                url=url,
                mediatype=b'application/mercurial-cbor')

            return {b'objs': [response]}

        if self.cacheobjects:
            return {
                b'objs': entry,
            }
        else:
            return {
                b'objs': [wireprototypes.encodedresponse(entry)],
            }

    def onobject(self, obj):
        if self.cacheobjects:
            self.buffered.append(obj)
        else:
            self.buffered.extend(self.encodefn(obj))

        yield obj

    def onfinished(self):
        self.ui.log(b'simplecache', b'storing cache entry for %s\n', self.key)
        if self.cacheobjects:
            CACHE[self.key] = self.buffered
        else:
            CACHE[self.key] = b''.join(self.buffered)

        return []

def makeresponsecacher(orig, repo, proto, command, args, objencoderfn,
                       redirecttargets, redirecthashes):
    return memorycacher(repo.ui, command, objencoderfn, redirecttargets,
                        redirecthashes, proto._req)

def loadredirecttargets(ui):
    path = ui.config(b'simplecache', b'redirectsfile')
    if not path:
        return []

    with open(path, 'rb') as fh:
        s = fh.read()

    return stringutil.evalpythonliteral(s)

def getadvertisedredirecttargets(orig, repo, proto):
    return loadredirecttargets(repo.ui)

def extsetup(ui):
    global CACHE

    CACHE = util.lrucachedict(10000)

    extensions.wrapfunction(wireprotov2server, b'makeresponsecacher',
                            makeresponsecacher)
    extensions.wrapfunction(wireprotov2server, b'getadvertisedredirecttargets',
                            getadvertisedredirecttargets)