hgweb: establish class for holding per request context

Currently, hgweb applications have many instance variables holding
mutated state. This is somewhat problematic because multiple threads
may race accessing or changing this state.

This patch starts a series that will add more thread safety to
hgweb applications. It will do this by moving mutated state out
of hgweb and into per-request instances of the newly established
"requestcontext" class.

Our new class currently behaves like a proxy to hgweb instances. This
should change once all state is captured in it instead of hgweb. The
effectiveness of this proxy is demonstrated by passing instances of
it - not hgweb instances/self - to various functions.

mercurial/hgweb/hgweb_mod.py

@@ -1,447 +1,467 b''
 # hgweb/hgweb_mod.py - Web interface for a repository.
 #
 # Copyright 21 May 2005 - (c) 2005 Jake Edge <[e-mail]>
 # Copyright 2005-2007 Matt Mackall <[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.
 
 import os, re
 from mercurial import ui, hg, hook, error, encoding, templater, util, repoview
 from mercurial.templatefilters import websub
 from mercurial.i18n import _
 from common import get_stat, ErrorResponse, permhooks, caching
 from common import HTTP_OK, HTTP_NOT_MODIFIED, HTTP_BAD_REQUEST
 from common import HTTP_NOT_FOUND, HTTP_SERVER_ERROR
 from request import wsgirequest
 import webcommands, protocol, webutil
 
 perms = {
     'changegroup': 'pull',
     'changegroupsubset': 'pull',
     'getbundle': 'pull',
     'stream_out': 'pull',
     'listkeys': 'pull',
     'unbundle': 'push',
     'pushkey': 'push',
 }
 
 ## Files of interest
 # Used to check if the repository has changed looking at mtime and size of
 # theses files. This should probably be relocated a bit higher in core.
 foi = [('spath', '00changelog.i'),
        ('spath', 'phaseroots'), # ! phase can change content at the same size
        ('spath', 'obsstore'),
        ('path', 'bookmarks'), # ! bookmark can change content at the same size
       ]
 
 def makebreadcrumb(url, prefix=''):
     '''Return a 'URL breadcrumb' list
 
     A 'URL breadcrumb' is a list of URL-name pairs,
     corresponding to each of the path items on a URL.
     This can be used to create path navigation entries.
     '''
     if url.endswith('/'):
         url = url[:-1]
     if prefix:
         url = '/' + prefix + url
     relpath = url
     if relpath.startswith('/'):
         relpath = relpath[1:]
 
     breadcrumb = []
     urlel = url
     pathitems = [''] + relpath.split('/')
     for pathel in reversed(pathitems):
         if not pathel or not urlel:
             break
         breadcrumb.append({'url': urlel, 'name': pathel})
         urlel = os.path.dirname(urlel)
     return reversed(breadcrumb)
 
 
+class requestcontext(object):
+    """Holds state/context for an individual request.
+
+    Servers can be multi-threaded. Holding state on the WSGI application
+    is prone to race conditions. Instances of this class exist to hold
+    mutable and race-free state for requests.
+    """
+    def __init__(self, app):
+        object.__setattr__(self, 'app', app)
+        object.__setattr__(self, 'repo', app.repo)
+
+    # Proxy unknown reads and writes to the application instance
+    # until everything is moved to us.
+    def __getattr__(self, name):
+        return getattr(self.app, name)
+
+    def __setattr__(self, name, value):
+        return setattr(self.app, name, value)
+
 class hgweb(object):
     """HTTP server for individual repositories.
 
     Instances of this class serve HTTP responses for a particular
     repository.
 
     Instances are typically used as WSGI applications.
 
     Some servers are multi-threaded. On these servers, there may
     be multiple active threads inside __call__.
     """
     def __init__(self, repo, name=None, baseui=None):
         if isinstance(repo, str):
             if baseui:
                 u = baseui.copy()
             else:
                 u = ui.ui()
             r = hg.repository(u, repo)
         else:
             # we trust caller to give us a private copy
             r = repo
 
         r = self._getview(r)
         r.ui.setconfig('ui', 'report_untrusted', 'off', 'hgweb')
         r.baseui.setconfig('ui', 'report_untrusted', 'off', 'hgweb')
         r.ui.setconfig('ui', 'nontty', 'true', 'hgweb')
         r.baseui.setconfig('ui', 'nontty', 'true', 'hgweb')
         # displaying bundling progress bar while serving feel wrong and may
         # break some wsgi implementation.
         r.ui.setconfig('progress', 'disable', 'true', 'hgweb')
         r.baseui.setconfig('progress', 'disable', 'true', 'hgweb')
         self.repo = r
         hook.redirect(True)
         self.repostate = ((-1, -1), (-1, -1))
         self.mtime = -1
         self.reponame = name
         self.archives = 'zip', 'gz', 'bz2'
         self.stripecount = 1
         # a repo owner may set web.templates in .hg/hgrc to get any file
         # readable by the user running the CGI script
         self.templatepath = self.config('web', 'templates')
         self.websubtable = self.loadwebsub()
 
     # The CGI scripts are often run by a user different from the repo owner.
     # Trust the settings from the .hg/hgrc files by default.
     def config(self, section, name, default=None, untrusted=True):
         return self.repo.ui.config(section, name, default,
                                    untrusted=untrusted)
 
     def configbool(self, section, name, default=False, untrusted=True):
         return self.repo.ui.configbool(section, name, default,
                                        untrusted=untrusted)
 
     def configlist(self, section, name, default=None, untrusted=True):
         return self.repo.ui.configlist(section, name, default,
                                        untrusted=untrusted)
 
     def _getview(self, repo):
         """The 'web.view' config controls changeset filter to hgweb. Possible
         values are ``served``, ``visible`` and ``all``. Default is ``served``.
         The ``served`` filter only shows changesets that can be pulled from the
         hgweb instance.  The``visible`` filter includes secret changesets but
         still excludes "hidden" one.
 
         See the repoview module for details.
 
         The option has been around undocumented since Mercurial 2.5, but no
         user ever asked about it. So we better keep it undocumented for now."""
         viewconfig = repo.ui.config('web', 'view', 'served',
                                     untrusted=True)
         if viewconfig == 'all':
             return repo.unfiltered()
         elif viewconfig in repoview.filtertable:
             return repo.filtered(viewconfig)
         else:
             return repo.filtered('served')
 
     def refresh(self, request):
         repostate = []
         # file of interrests mtime and size
         for meth, fname in foi:
             prefix = getattr(self.repo, meth)
             st = get_stat(prefix, fname)
             repostate.append((st.st_mtime, st.st_size))
         repostate = tuple(repostate)
         # we need to compare file size in addition to mtime to catch
         # changes made less than a second ago
         if repostate != self.repostate:
             r = hg.repository(self.repo.baseui, self.repo.url())
             self.repo = self._getview(r)
             self.maxchanges = int(self.config("web", "maxchanges", 10))
             self.stripecount = int(self.config("web", "stripes", 1))
             self.maxshortchanges = int(self.config("web", "maxshortchanges",
                                                    60))
             self.maxfiles = int(self.config("web", "maxfiles", 10))
             self.allowpull = self.configbool("web", "allowpull", True)
             encoding.encoding = self.config("web", "encoding",
                                             encoding.encoding)
             # update these last to avoid threads seeing empty settings
             self.repostate = repostate
             # mtime is needed for ETag
             self.mtime = st.st_mtime
 
         self.repo.ui.environ = request.env
 
     def run(self):
         """Start a server from CGI environment.
 
         Modern servers should be using WSGI and should avoid this
         method, if possible.
         """
         if not os.environ.get('GATEWAY_INTERFACE', '').startswith("CGI/1."):
             raise RuntimeError("This function is only intended to be "
                                "called while running as a CGI script.")
         import mercurial.hgweb.wsgicgi as wsgicgi
         wsgicgi.launch(self)
 
     def __call__(self, env, respond):
         """Run the WSGI application.
 
         This may be called by multiple threads.
         """
         req = wsgirequest(env, respond)
         return self.run_wsgi(req)
 
     def run_wsgi(self, req):
         """Internal method to run the WSGI application.
 
         This is typically only called by Mercurial. External consumers
         should be using instances of this class as the WSGI application.
         """
         self.refresh(req)
+        rctx = requestcontext(self)
 
         # work with CGI variables to create coherent structure
         # use SCRIPT_NAME, PATH_INFO and QUERY_STRING as well as our REPO_NAME
 
         req.url = req.env['SCRIPT_NAME']
         if not req.url.endswith('/'):
             req.url += '/'
         if 'REPO_NAME' in req.env:
             req.url += req.env['REPO_NAME'] + '/'
 
         if 'PATH_INFO' in req.env:
             parts = req.env['PATH_INFO'].strip('/').split('/')
             repo_parts = req.env.get('REPO_NAME', '').split('/')
             if parts[:len(repo_parts)] == repo_parts:
                 parts = parts[len(repo_parts):]
             query = '/'.join(parts)
         else:
             query = req.env['QUERY_STRING'].split('&', 1)[0]
             query = query.split(';', 1)[0]
 
         # process this if it's a protocol request
         # protocol bits don't need to create any URLs
         # and the clients always use the old URL structure
 
         cmd = req.form.get('cmd', [''])[0]
         if protocol.iscmd(cmd):
             try:
                 if query:
                     raise ErrorResponse(HTTP_NOT_FOUND)
                 if cmd in perms:
-                    self.check_perm(req, perms[cmd])
+                    self.check_perm(rctx, req, perms[cmd])
                 return protocol.call(self.repo, req, cmd)
             except ErrorResponse as inst:
                 # A client that sends unbundle without 100-continue will
                 # break if we respond early.
                 if (cmd == 'unbundle' and
                     (req.env.get('HTTP_EXPECT',
                                  '').lower() != '100-continue') or
                     req.env.get('X-HgHttp2', '')):
                     req.drain()
                 else:
                     req.headers.append(('Connection', 'Close'))
                 req.respond(inst, protocol.HGTYPE,
                             body='0\n%s\n' % inst.message)
                 return ''
 
         # translate user-visible url structure to internal structure
 
         args = query.split('/', 2)
         if 'cmd' not in req.form and args and args[0]:
 
             cmd = args.pop(0)
             style = cmd.rfind('-')
             if style != -1:
                 req.form['style'] = [cmd[:style]]
                 cmd = cmd[style + 1:]
 
             # avoid accepting e.g. style parameter as command
             if util.safehasattr(webcommands, cmd):
                 req.form['cmd'] = [cmd]
 
             if cmd == 'static':
                 req.form['file'] = ['/'.join(args)]
             else:
                 if args and args[0]:
                     node = args.pop(0).replace('%2F', '/')
                     req.form['node'] = [node]
                 if args:
                     req.form['file'] = args
 
             ua = req.env.get('HTTP_USER_AGENT', '')
             if cmd == 'rev' and 'mercurial' in ua:
                 req.form['style'] = ['raw']
 
             if cmd == 'archive':
                 fn = req.form['node'][0]
                 for type_, spec in self.archive_specs.iteritems():
                     ext = spec[2]
                     if fn.endswith(ext):
                         req.form['node'] = [fn[:-len(ext)]]
                         req.form['type'] = [type_]
 
         # process the web interface request
 
         try:
             tmpl = self.templater(req)
             ctype = tmpl('mimetype', encoding=encoding.encoding)
             ctype = templater.stringify(ctype)
 
             # check read permissions non-static content
             if cmd != 'static':
-                self.check_perm(req, None)
+                self.check_perm(rctx, req, None)
 
             if cmd == '':
                 req.form['cmd'] = [tmpl.cache['default']]
                 cmd = req.form['cmd'][0]
 
             if self.configbool('web', 'cache', True):
                 caching(self, req) # sets ETag header or raises NOT_MODIFIED
             if cmd not in webcommands.__all__:
                 msg = 'no such method: %s' % cmd
                 raise ErrorResponse(HTTP_BAD_REQUEST, msg)
             elif cmd == 'file' and 'raw' in req.form.get('style', []):
                 self.ctype = ctype
-                content = webcommands.rawfile(self, req, tmpl)
+                content = webcommands.rawfile(rctx, req, tmpl)
             else:
-                content = getattr(webcommands, cmd)(self, req, tmpl)
+                content = getattr(webcommands, cmd)(rctx, req, tmpl)
                 req.respond(HTTP_OK, ctype)
 
             return content
 
         except (error.LookupError, error.RepoLookupError) as err:
             req.respond(HTTP_NOT_FOUND, ctype)
             msg = str(err)
             if (util.safehasattr(err, 'name') and
                 not isinstance(err,  error.ManifestLookupError)):
                 msg = 'revision not found: %s' % err.name
             return tmpl('error', error=msg)
         except (error.RepoError, error.RevlogError) as inst:
             req.respond(HTTP_SERVER_ERROR, ctype)
             return tmpl('error', error=str(inst))
         except ErrorResponse as inst:
             req.respond(inst, ctype)
             if inst.code == HTTP_NOT_MODIFIED:
                 # Not allowed to return a body on a 304
                 return ['']
             return tmpl('error', error=inst.message)
 
     def loadwebsub(self):
         websubtable = []
         websubdefs = self.repo.ui.configitems('websub')
         # we must maintain interhg backwards compatibility
         websubdefs += self.repo.ui.configitems('interhg')
         for key, pattern in websubdefs:
             # grab the delimiter from the character after the "s"
             unesc = pattern[1]
             delim = re.escape(unesc)
 
             # identify portions of the pattern, taking care to avoid escaped
             # delimiters. the replace format and flags are optional, but
             # delimiters are required.
             match = re.match(
                 r'^s%s(.+)(?:(?<=\\\\)|(?<!\\))%s(.*)%s([ilmsux])*$'
                 % (delim, delim, delim), pattern)
             if not match:
                 self.repo.ui.warn(_("websub: invalid pattern for %s: %s\n")
                                   % (key, pattern))
                 continue
 
             # we need to unescape the delimiter for regexp and format
             delim_re = re.compile(r'(?<!\\)\\%s' % delim)
             regexp = delim_re.sub(unesc, match.group(1))
             format = delim_re.sub(unesc, match.group(2))
 
             # the pattern allows for 6 regexp flags, so set them if necessary
             flagin = match.group(3)
             flags = 0
             if flagin:
                 for flag in flagin.upper():
                     flags |= re.__dict__[flag]
 
             try:
                 regexp = re.compile(regexp, flags)
                 websubtable.append((regexp, format))
             except re.error:
                 self.repo.ui.warn(_("websub: invalid regexp for %s: %s\n")
                                   % (key, regexp))
         return websubtable
 
     def templater(self, req):
 
         # determine scheme, port and server name
         # this is needed to create absolute urls
 
         proto = req.env.get('wsgi.url_scheme')
         if proto == 'https':
             proto = 'https'
             default_port = "443"
         else:
             proto = 'http'
             default_port = "80"
 
         port = req.env["SERVER_PORT"]
         port = port != default_port and (":" + port) or ""
         urlbase = '%s://%s%s' % (proto, req.env['SERVER_NAME'], port)
         logourl = self.config("web", "logourl", "http://mercurial.selenic.com/")
         logoimg = self.config("web", "logoimg", "hglogo.png")
         staticurl = self.config("web", "staticurl") or req.url + 'static/'
         if not staticurl.endswith('/'):
             staticurl += '/'
 
         # some functions for the templater
 
         def motd(**map):
             yield self.config("web", "motd", "")
 
         # figure out which style to use
 
         vars = {}
         styles = (
             req.form.get('style', [None])[0],
             self.config('web', 'style'),
             'paper',
         )
         style, mapfile = templater.stylemap(styles, self.templatepath)
         if style == styles[0]:
             vars['style'] = style
 
         start = req.url[-1] == '?' and '&' or '?'
         sessionvars = webutil.sessionvars(vars, start)
 
         if not self.reponame:
             self.reponame = (self.config("web", "name")
                              or req.env.get('REPO_NAME')
                              or req.url.strip('/') or self.repo.root)
 
         def websubfilter(text):
             return websub(text, self.websubtable)
 
         # create the templater
 
         tmpl = templater.templater(mapfile,
                                    filters={"websub": websubfilter},
                                    defaults={"url": req.url,
                                              "logourl": logourl,
                                              "logoimg": logoimg,
                                              "staticurl": staticurl,
                                              "urlbase": urlbase,
                                              "repo": self.reponame,
                                              "encoding": encoding.encoding,
                                              "motd": motd,
                                              "sessionvars": sessionvars,
                                              "pathdef": makebreadcrumb(req.url),
                                              "style": style,
                                             })
         return tmpl
 
     def archivelist(self, nodeid):
         allowed = self.configlist("web", "allow_archive")
         for i, spec in self.archive_specs.iteritems():
             if i in allowed or self.configbool("web", "allow" + i):
                 yield {"type" : i, "extension" : spec[2], "node" : nodeid}
 
     archive_specs = {
         'bz2': ('application/x-bzip2', 'tbz2', '.tar.bz2', None),
         'gz': ('application/x-gzip', 'tgz', '.tar.gz', None),
         'zip': ('application/zip', 'zip', '.zip', None),
         }
 
-    def check_perm(self, req, op):
+    def check_perm(self, rctx, req, op):
         for permhook in permhooks:
-            permhook(self, req, op)
+            permhook(rctx, req, op)