inotify: server: use a common 'pollable' interface for server & repowatcher

Mainly for documentation purposes: it easily explains the role of handle_event
and handle_timeout, and why both server & repowatcher implement those methods.

hgext/inotify/server.py

@@ -1,793 +1,819 b''
 # server.py - inotify status server
 #
 # Copyright 2006, 2007, 2008 Bryan O'Sullivan <[e-mail]>
 # Copyright 2007, 2008 Brendan Cully <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2, incorporated herein by reference.
 
 from mercurial.i18n import _
 from mercurial import osutil, util
 import common
 import errno, os, select, socket, stat, struct, sys, tempfile, time
 
 try:
     import linux as inotify
     from linux import watcher
 except ImportError:
     raise
 
 class AlreadyStartedException(Exception): pass
 
 def join(a, b):
     if a:
         if a[-1] == '/':
             return a + b
         return a + '/' + b
     return b
 
 walk_ignored_errors = (errno.ENOENT, errno.ENAMETOOLONG)
 
 def walkrepodirs(repo):
     '''Iterate over all subdirectories of this repo.
     Exclude the .hg directory, any nested repos, and ignored dirs.'''
     rootslash = repo.root + os.sep
 
     def walkit(dirname, top):
         fullpath = rootslash + dirname
         try:
             for name, kind in osutil.listdir(fullpath):
                 if kind == stat.S_IFDIR:
                     if name == '.hg':
                         if not top:
                             return
                     else:
                         d = join(dirname, name)
                         if repo.dirstate._ignore(d):
                             continue
                         for subdir in walkit(d, False):
                             yield subdir
         except OSError, err:
             if err.errno not in walk_ignored_errors:
                 raise
         yield fullpath
 
     return walkit('', True)
 
 def walk(repo, root):
     '''Like os.walk, but only yields regular files.'''
 
     # This function is critical to performance during startup.
 
     rootslash = repo.root + os.sep
 
     def walkit(root, reporoot):
         files, dirs = [], []
 
         try:
             fullpath = rootslash + root
             for name, kind in osutil.listdir(fullpath):
                 if kind == stat.S_IFDIR:
                     if name == '.hg':
                         if not reporoot:
                             return
                     else:
                         dirs.append(name)
                         path = join(root, name)
                         if repo.dirstate._ignore(path):
                             continue
                         for result in walkit(path, False):
                             yield result
                 elif kind in (stat.S_IFREG, stat.S_IFLNK):
                     files.append(name)
             yield fullpath, dirs, files
 
         except OSError, err:
             if err.errno not in walk_ignored_errors:
                 raise
 
     return walkit(root, root == '')
 
 def _explain_watch_limit(ui, repo, count):
     path = '/proc/sys/fs/inotify/max_user_watches'
     try:
         limit = int(file(path).read())
     except IOError, err:
         if err.errno != errno.ENOENT:
             raise
         raise util.Abort(_('this system does not seem to '
                            'support inotify'))
     ui.warn(_('*** the current per-user limit on the number '
               'of inotify watches is %s\n') % limit)
     ui.warn(_('*** this limit is too low to watch every '
               'directory in this repository\n'))
     ui.warn(_('*** counting directories: '))
     ndirs = len(list(walkrepodirs(repo)))
     ui.warn(_('found %d\n') % ndirs)
     newlimit = min(limit, 1024)
     while newlimit < ((limit + ndirs) * 1.1):
         newlimit *= 2
     ui.warn(_('*** to raise the limit from %d to %d (run as root):\n') %
             (limit, newlimit))
     ui.warn(_('***  echo %d > %s\n') % (newlimit, path))
     raise util.Abort(_('cannot watch %s until inotify watch limit is raised')
                      % repo.root)
 
-class repowatcher(object):
+class pollable(object):
+    """
+    Interface to support polling.
+    The file descriptor returned by fileno() is registered to a polling
+    object.
+    Usage:
+        Every tick, check if an event has happened since the last tick:
+        * If yes, call handle_events
+        * If no, call handle_timeout
+    """
     poll_events = select.POLLIN
+    def fileno(self):
+        raise NotImplementedError
+
+    def handle_events(self, events):
+        raise NotImplementedError
+
+    def handle_timeout(self):
+        raise NotImplementedError
+
+    def shutdown(self):
+        raise NotImplementedError
+
+class repowatcher(pollable):
+    """
+    Watches inotify events
+    """
     statuskeys = 'almr!?'
     mask = (
         inotify.IN_ATTRIB |
         inotify.IN_CREATE |
         inotify.IN_DELETE |
         inotify.IN_DELETE_SELF |
         inotify.IN_MODIFY |
         inotify.IN_MOVED_FROM |
         inotify.IN_MOVED_TO |
         inotify.IN_MOVE_SELF |
         inotify.IN_ONLYDIR |
         inotify.IN_UNMOUNT |
         0)
 
     def __init__(self, ui, repo, master):
         self.ui = ui
         self.repo = repo
         self.wprefix = self.repo.wjoin('')
         self.timeout = None
         self.master = master
         try:
             self.watcher = watcher.watcher()
         except OSError, err:
             raise util.Abort(_('inotify service not available: %s') %
                              err.strerror)
         self.threshold = watcher.threshold(self.watcher)
         self.registered = True
         self.fileno = self.watcher.fileno
 
         self.tree = {}
         self.statcache = {}
         self.statustrees = dict([(s, {}) for s in self.statuskeys])
 
         self.watches = 0
         self.last_event = None
 
         self.lastevent = {}
 
         self.ds_info = self.dirstate_info()
         self.handle_timeout()
         self.scan()
 
     def event_time(self):
         last = self.last_event
         now = time.time()
         self.last_event = now
 
         if last is None:
             return 'start'
         delta = now - last
         if delta < 5:
             return '+%.3f' % delta
         if delta < 50:
             return '+%.2f' % delta
         return '+%.1f' % delta
 
     def dirstate_info(self):
         try:
             st = os.lstat(self.repo.join('dirstate'))
             return st.st_mtime, st.st_ino
         except OSError, err:
             if err.errno != errno.ENOENT:
                 raise
             return 0, 0
 
     def add_watch(self, path, mask):
         if not path:
             return
         if self.watcher.path(path) is None:
             if self.ui.debugflag:
                 self.ui.note(_('watching %r\n') % path[len(self.wprefix):])
             try:
                 self.watcher.add(path, mask)
                 self.watches += 1
             except OSError, err:
                 if err.errno in (errno.ENOENT, errno.ENOTDIR):
                     return
                 if err.errno != errno.ENOSPC:
                     raise
                 _explain_watch_limit(self.ui, self.repo, self.watches)
 
     def setup(self):
         self.ui.note(_('watching directories under %r\n') % self.repo.root)
         self.add_watch(self.repo.path, inotify.IN_DELETE)
         self.check_dirstate()
 
     def wpath(self, evt):
         path = evt.fullpath
         if path == self.repo.root:
             return ''
         if path.startswith(self.wprefix):
             return path[len(self.wprefix):]
         raise 'wtf? ' + path
 
     def dir(self, tree, path):
         if path:
             for name in path.split('/'):
                 tree = tree.setdefault(name, {})
         return tree
 
     def lookup(self, path, tree):
         if path:
             try:
                 for name in path.split('/'):
                     tree = tree[name]
             except KeyError:
                 return 'x'
             except TypeError:
                 return 'd'
         return tree
 
     def split(self, path):
         c = path.rfind('/')
         if c == -1:
             return '', path
         return path[:c], path[c+1:]
 
     def filestatus(self, fn, st):
         try:
             type_, mode, size, time = self.repo.dirstate._map[fn][:4]
         except KeyError:
             type_ = '?'
         if type_ == 'n':
             st_mode, st_size, st_mtime = st
             if size == -1:
                 return 'l'
             if size and (size != st_size or (mode ^ st_mode) & 0100):
                 return 'm'
             if time != int(st_mtime):
                 return 'l'
             return 'n'
         if type_ == '?' and self.repo.dirstate._ignore(fn):
             return 'i'
         return type_
 
     def updatefile(self, wfn, osstat):
         '''
         update the file entry of an existing file.
 
         osstat: (mode, size, time) tuple, as returned by os.lstat(wfn)
         '''
 
         self._updatestatus(wfn, self.filestatus(wfn, osstat))
 
     def deletefile(self, wfn, oldstatus):
         '''
         update the entry of a file which has been deleted.
 
         oldstatus: char in statuskeys, status of the file before deletion
         '''
         if oldstatus == 'r':
             newstatus = 'r'
         elif oldstatus in 'almn':
             newstatus = '!'
         else:
             newstatus = None
 
         self.statcache.pop(wfn, None)
         self._updatestatus(wfn, newstatus)
 
     def _updatestatus(self, wfn, newstatus):
         '''
         Update the stored status of a file or directory.
 
         newstatus: - char in (statuskeys + 'ni'), new status to apply.
                    - or None, to stop tracking wfn
         '''
         root, fn = self.split(wfn)
         d = self.dir(self.tree, root)
 
         oldstatus = d.get(fn)
         # oldstatus can be either:
         # - None : fn is new
         # - a char in statuskeys: fn is a (tracked) file
         # - a dict: fn is a directory
         isdir = isinstance(oldstatus, dict)
 
         if self.ui.debugflag and oldstatus != newstatus:
             if isdir:
                 self.ui.note(_('status: %r dir(%d) -> %s\n') %
                              (wfn, len(oldstatus), newstatus))
             else:
                 self.ui.note(_('status: %r %s -> %s\n') %
                              (wfn, oldstatus, newstatus))
         if not isdir:
             if oldstatus and oldstatus in self.statuskeys \
                 and oldstatus != newstatus:
                 del self.dir(self.statustrees[oldstatus], root)[fn]
             if newstatus and newstatus != 'i':
                 d[fn] = newstatus
                 if newstatus in self.statuskeys:
                     dd = self.dir(self.statustrees[newstatus], root)
                     if oldstatus != newstatus or fn not in dd:
                         dd[fn] = newstatus
             else:
                 d.pop(fn, None)
 
 
     def check_deleted(self, key):
         # Files that had been deleted but were present in the dirstate
         # may have vanished from the dirstate; we must clean them up.
         nuke = []
         for wfn, ignore in self.walk(key, self.statustrees[key]):
             if wfn not in self.repo.dirstate:
                 nuke.append(wfn)
         for wfn in nuke:
             root, fn = self.split(wfn)
             del self.dir(self.statustrees[key], root)[fn]
             del self.dir(self.tree, root)[fn]
 
     def scan(self, topdir=''):
         ds = self.repo.dirstate._map.copy()
         self.add_watch(join(self.repo.root, topdir), self.mask)
         for root, dirs, files in walk(self.repo, topdir):
             for d in dirs:
                 self.add_watch(join(root, d), self.mask)
             wroot = root[len(self.wprefix):]
             d = self.dir(self.tree, wroot)
             for fn in files:
                 wfn = join(wroot, fn)
                 self.updatefile(wfn, self.getstat(wfn))
                 ds.pop(wfn, None)
         wtopdir = topdir
         if wtopdir and wtopdir[-1] != '/':
             wtopdir += '/'
         for wfn, state in ds.iteritems():
             if not wfn.startswith(wtopdir):
                 continue
             try:
                 st = self.stat(wfn)
             except OSError:
                 status = state[0]
                 self.deletefile(wfn, status)
             else:
                 self.updatefile(wfn, st)
         self.check_deleted('!')
         self.check_deleted('r')
 
     def check_dirstate(self):
         ds_info = self.dirstate_info()
         if ds_info == self.ds_info:
             return
         self.ds_info = ds_info
         if not self.ui.debugflag:
             self.last_event = None
         self.ui.note(_('%s dirstate reload\n') % self.event_time())
         self.repo.dirstate.invalidate()
         self.handle_timeout()
         self.scan()
         self.ui.note(_('%s end dirstate reload\n') % self.event_time())
 
     def walk(self, states, tree, prefix=''):
         # This is the "inner loop" when talking to the client.
 
         for name, val in tree.iteritems():
             path = join(prefix, name)
             try:
                 if val in states:
                     yield path, val
             except TypeError:
                 for p in self.walk(states, val, path):
                     yield p
 
     def update_hgignore(self):
         # An update of the ignore file can potentially change the
         # states of all unknown and ignored files.
 
         # XXX If the user has other ignore files outside the repo, or
         # changes their list of ignore files at run time, we'll
         # potentially never see changes to them.  We could get the
         # client to report to us what ignore data they're using.
         # But it's easier to do nothing than to open that can of
         # worms.
 
         if '_ignore' in self.repo.dirstate.__dict__:
             delattr(self.repo.dirstate, '_ignore')
             self.ui.note(_('rescanning due to .hgignore change\n'))
             self.handle_timeout()
             self.scan()
 
     def getstat(self, wpath):
         try:
             return self.statcache[wpath]
         except KeyError:
             try:
                 return self.stat(wpath)
             except OSError, err:
                 if err.errno != errno.ENOENT:
                     raise
 
     def stat(self, wpath):
         try:
             st = os.lstat(join(self.wprefix, wpath))
             ret = st.st_mode, st.st_size, st.st_mtime
             self.statcache[wpath] = ret
             return ret
         except OSError:
             self.statcache.pop(wpath, None)
             raise
 
     def eventaction(code):
         def decorator(f):
             def wrapper(self, wpath):
                 if code == 'm' and wpath in self.lastevent and \
                     self.lastevent[wpath] in 'cm':
                     return
                 self.lastevent[wpath] = code
                 self.timeout = 250
 
                 f(self, wpath)
 
             wrapper.func_name = f.func_name
             return wrapper
         return decorator
 
     @eventaction('c')
     def created(self, wpath):
         if wpath == '.hgignore':
             self.update_hgignore()
         try:
             st = self.stat(wpath)
             if stat.S_ISREG(st[0]):
                 self.updatefile(wpath, st)
         except OSError:
             pass
 
     @eventaction('m')
     def modified(self, wpath):
         if wpath == '.hgignore':
             self.update_hgignore()
         try:
             st = self.stat(wpath)
             if stat.S_ISREG(st[0]):
                 if self.repo.dirstate[wpath] in 'lmn':
                     self.updatefile(wpath, st)
         except OSError:
             pass
 
     @eventaction('d')
     def deleted(self, wpath):
         if wpath == '.hgignore':
             self.update_hgignore()
         elif wpath.startswith('.hg/'):
             if wpath == '.hg/wlock':
                 self.check_dirstate()
             return
 
         self.deletefile(wpath, self.repo.dirstate[wpath])
 
     def process_create(self, wpath, evt):
         if self.ui.debugflag:
             self.ui.note(_('%s event: created %s\n') %
                          (self.event_time(), wpath))
 
         if evt.mask & inotify.IN_ISDIR:
             self.scan(wpath)
         else:
             self.created(wpath)
 
     def process_delete(self, wpath, evt):
         if self.ui.debugflag:
             self.ui.note(_('%s event: deleted %s\n') %
                          (self.event_time(), wpath))
 
         if evt.mask & inotify.IN_ISDIR:
             tree = self.dir(self.tree, wpath).copy()
             for wfn, ignore in self.walk('?', tree):
                 self.deletefile(join(wpath, wfn), '?')
             self.scan(wpath)
         else:
             self.deleted(wpath)
 
     def process_modify(self, wpath, evt):
         if self.ui.debugflag:
             self.ui.note(_('%s event: modified %s\n') %
                          (self.event_time(), wpath))
 
         if not (evt.mask & inotify.IN_ISDIR):
             self.modified(wpath)
 
     def process_unmount(self, evt):
         self.ui.warn(_('filesystem containing %s was unmounted\n') %
                      evt.fullpath)
         sys.exit(0)
 
     def handle_pollevents(self, events):
         if self.ui.debugflag:
             self.ui.note(_('%s readable: %d bytes\n') %
                          (self.event_time(), self.threshold.readable()))
         if not self.threshold():
             if self.registered:
                 if self.ui.debugflag:
                     self.ui.note(_('%s below threshold - unhooking\n') %
                                  (self.event_time()))
                 self.master.poll.unregister(self.fileno())
                 self.registered = False
                 self.timeout = 250
         else:
             self.read_events()
 
     def read_events(self, bufsize=None):
         events = self.watcher.read(bufsize)
         if self.ui.debugflag:
             self.ui.note(_('%s reading %d events\n') %
                          (self.event_time(), len(events)))
         for evt in events:
             wpath = self.wpath(evt)
             if evt.mask & inotify.IN_UNMOUNT:
                 self.process_unmount(wpath, evt)
             elif evt.mask & (inotify.IN_MODIFY | inotify.IN_ATTRIB):
                 self.process_modify(wpath, evt)
             elif evt.mask & (inotify.IN_DELETE | inotify.IN_DELETE_SELF |
                              inotify.IN_MOVED_FROM):
                 self.process_delete(wpath, evt)
             elif evt.mask & (inotify.IN_CREATE | inotify.IN_MOVED_TO):
                 self.process_create(wpath, evt)
 
         self.lastevent.clear()
 
     def handle_timeout(self):
         if not self.registered:
             if self.ui.debugflag:
                 self.ui.note(_('%s hooking back up with %d bytes readable\n') %
                              (self.event_time(), self.threshold.readable()))
             self.read_events(0)
-            self.master.poll.register(self, select.POLLIN)
+            self.master.poll.register(self, self.poll_events)
             self.registered = True
 
         self.timeout = None
 
     def shutdown(self):
         self.watcher.close()
 
     def debug(self):
         """
         Returns a sorted list of relatives paths currently watched,
         for debugging purposes.
         """
         return sorted(tuple[0][len(self.wprefix):] for tuple in self.watcher)
 
-class server(object):
-    poll_events = select.POLLIN
-
+class server(pollable):
+    """
+    Listens for client queries on unix socket inotify.sock
+    """
     def __init__(self, ui, repo, repowatcher, timeout):
         self.ui = ui
         self.repo = repo
         self.repowatcher = repowatcher
         self.timeout = timeout
         self.sock = socket.socket(socket.AF_UNIX)
         self.sockpath = self.repo.join('inotify.sock')
         self.realsockpath = None
         try:
             self.sock.bind(self.sockpath)
         except socket.error, err:
             if err[0] == errno.EADDRINUSE:
                 raise AlreadyStartedException(_('could not start server: %s')
                                               % err[1])
             if err[0] == "AF_UNIX path too long":
                 tempdir = tempfile.mkdtemp(prefix="hg-inotify-")
                 self.realsockpath = os.path.join(tempdir, "inotify.sock")
                 try:
                     self.sock.bind(self.realsockpath)
                     os.symlink(self.realsockpath, self.sockpath)
                 except (OSError, socket.error), inst:
                     try:
                         os.unlink(self.realsockpath)
                     except:
                         pass
                     os.rmdir(tempdir)
                     if inst.errno == errno.EEXIST:
                         raise AlreadyStartedException(_('could not start server: %s')
                                                       % inst.strerror)
                     raise
             else:
                 raise
         self.sock.listen(5)
         self.fileno = self.sock.fileno
 
     def handle_timeout(self):
         pass
 
     def answer_stat_query(self, cs):
         names = cs.read().split('\0')
 
         states = names.pop()
 
         self.ui.note(_('answering query for %r\n') % states)
 
         if self.repowatcher.timeout:
             # We got a query while a rescan is pending.  Make sure we
             # rescan before responding, or we could give back a wrong
             # answer.
             self.repowatcher.handle_timeout()
 
         if not names:
             def genresult(states, tree):
                 for fn, state in self.repowatcher.walk(states, tree):
                     yield fn
         else:
             def genresult(states, tree):
                 for fn in names:
                     l = self.repowatcher.lookup(fn, tree)
                     try:
                         if l in states:
                             yield fn
                     except TypeError:
                         for f, s in self.repowatcher.walk(states, l, fn):
                             yield f
 
         return ['\0'.join(r) for r in [
             genresult('l', self.repowatcher.statustrees['l']),
             genresult('m', self.repowatcher.statustrees['m']),
             genresult('a', self.repowatcher.statustrees['a']),
             genresult('r', self.repowatcher.statustrees['r']),
             genresult('!', self.repowatcher.statustrees['!']),
             '?' in states
                 and genresult('?', self.repowatcher.statustrees['?'])
                 or [],
             [],
             'c' in states and genresult('n', self.repowatcher.tree) or [],
             ]]
 
     def answer_dbug_query(self):
         return ['\0'.join(self.repowatcher.debug())]
 
     def handle_pollevents(self, events):
         for e in events:
             self.handle_pollevent()
 
     def handle_pollevent(self):
         sock, addr = self.sock.accept()
 
         cs = common.recvcs(sock)
         version = ord(cs.read(1))
 
         if version != common.version:
             self.ui.warn(_('received query from incompatible client '
                            'version %d\n') % version)
             return
 
         type = cs.read(4)
 
         if type == 'STAT':
             results = self.answer_stat_query(cs)
         elif type == 'DBUG':
             results = self.answer_dbug_query()
         else:
             self.ui.warn(_('unrecognized query type: %s\n') % type)
             return
 
         try:
             try:
                 v = chr(common.version)
 
                 sock.sendall(v + type + struct.pack(common.resphdrfmts[type],
                                             *map(len, results)))
                 sock.sendall(''.join(results))
             finally:
                 sock.shutdown(socket.SHUT_WR)
         except socket.error, err:
             if err[0] != errno.EPIPE:
                 raise
 
     def shutdown(self):
         self.sock.close()
         try:
             os.unlink(self.sockpath)
             if self.realsockpath:
                 os.unlink(self.realsockpath)
                 os.rmdir(os.path.dirname(self.realsockpath))
         except OSError, err:
             if err.errno != errno.ENOENT:
                 raise
 
 class master(object):
     def __init__(self, ui, repo, timeout=None):
         self.ui = ui
         self.repo = repo
         self.poll = select.poll()
         self.repowatcher = repowatcher(ui, repo, self)
         self.server = server(ui, repo, self.repowatcher, timeout)
         self.table = {}
         for obj in (self.repowatcher, self.server):
             fd = obj.fileno()
             self.table[fd] = obj
             self.poll.register(fd, obj.poll_events)
 
     def register(self, fd, mask):
         self.poll.register(fd, mask)
 
     def shutdown(self):
         for obj in self.table.itervalues():
             obj.shutdown()
 
     def run(self):
         self.repowatcher.setup()
         self.ui.note(_('finished setup\n'))
         if os.getenv('TIME_STARTUP'):
             sys.exit(0)
         while True:
             timeout = None
             timeobj = None
             for obj in self.table.itervalues():
                 if obj.timeout is not None and (timeout is None or obj.timeout < timeout):
                     timeout, timeobj = obj.timeout, obj
             try:
                 if self.ui.debugflag:
                     if timeout is None:
                         self.ui.note(_('polling: no timeout\n'))
                     else:
                         self.ui.note(_('polling: %sms timeout\n') % timeout)
                 events = self.poll.poll(timeout)
             except select.error, err:
                 if err[0] == errno.EINTR:
                     continue
                 raise
             if events:
                 by_fd = {}
                 for fd, event in events:
                     by_fd.setdefault(fd, []).append(event)
 
                 for fd, events in by_fd.iteritems():
                     self.table[fd].handle_pollevents(events)
 
             elif timeobj:
                 timeobj.handle_timeout()
 
 def start(ui, repo):
     def closefds(ignore):
         # (from python bug #1177468)
         # close all inherited file descriptors
         # Python 2.4.1 and later use /dev/urandom to seed the random module's RNG
         # a file descriptor is kept internally as os._urandomfd (created on demand
         # the first time os.urandom() is called), and should not be closed
         try:
             os.urandom(4)
             urandom_fd = getattr(os, '_urandomfd', None)
         except AttributeError:
             urandom_fd = None
         ignore.append(urandom_fd)
         for fd in range(3, 256):
             if fd in ignore:
                 continue
             try:
                 os.close(fd)
             except OSError:
                 pass
 
     m = master(ui, repo)
     sys.stdout.flush()
     sys.stderr.flush()
 
     pid = os.fork()
     if pid:
         return pid
 
     closefds([m.server.fileno(), m.repowatcher.fileno()])
     os.setsid()
 
     fd = os.open('/dev/null', os.O_RDONLY)
     os.dup2(fd, 0)
     if fd > 0:
         os.close(fd)
 
     fd = os.open(ui.config('inotify', 'log', '/dev/null'),
                  os.O_RDWR | os.O_CREAT | os.O_TRUNC)
     os.dup2(fd, 1)
     os.dup2(fd, 2)
     if fd > 2:
         os.close(fd)
 
     try:
         m.run()
     finally:
         m.shutdown()
         os._exit(0)