view MoinMoin/caching.py @ 6111:1fdd537e9d83

SubProcess: reimplement exec_cmd subclassing Popen and overriding some methods isn't pretty. the code we have was written for py 2.4 or so and the py 2.7 Popen looked quite different. this way with the timer should be less problematic.
author Thomas Waldmann <tw AT waldmann-edv DOT de>
date Tue, 06 Sep 2016 04:39:28 +0200
parents 7e3e406f21d9
children
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# -*- coding: iso-8859-1 -*-
"""
    MoinMoin caching module

    @copyright: 2001-2004 by Juergen Hermann <jh@web.de>,
                2006-2009 MoinMoin:ThomasWaldmann,
                2008 MoinMoin:ThomasPfaff
    @license: GNU GPL, see COPYING for details.
"""

import os
import shutil
import tempfile

from MoinMoin import log
logging = log.getLogger(__name__)

from MoinMoin import config
from MoinMoin.util import filesys, lock, pickle, PICKLE_PROTOCOL


class CacheError(Exception):
    """ raised if we have trouble locking, reading or writing """
    pass


def get_arena_dir(request, arena, scope):
    if scope == 'item': # arena is a Page instance
        # we could move cache out of the page directory and store it to cache_dir
        return arena.getPagePath('cache', check_create=1)
    elif scope == 'wiki':
        return os.path.join(request.cfg.cache_dir, request.cfg.siteid, arena)
    elif scope == 'farm':
        return os.path.join(request.cfg.cache_dir, '__common__', arena)
    elif scope == 'userdir':
        return os.path.join(request.cfg.user_dir, 'cache', arena)
    elif scope == 'dir':
        # arena is a specific directory, just use it
        return arena
    return None


def get_cache_list(request, arena, scope):
    arena_dir = get_arena_dir(request, arena, scope)
    try:
        return os.listdir(arena_dir)
    except OSError:
        return []


class CacheEntry:
    def __init__(self, request, arena, key, scope='wiki', do_locking=True,
                 use_pickle=False, use_encode=False):
        """ init a cache entry
            @param request: the request object
            @param arena: either a string or a page object, when we want to use
                          page local cache area
            @param key: under which key we access the cache content
            @param scope: the scope where we are caching:
                          'item' - an item local cache
                          'wiki' - a wiki local cache
                          'farm' - a cache for the whole farm
                          'dir' - just use some specific directory
            @param do_locking: if there should be a lock, normally True
            @param use_pickle: if data should be pickled/unpickled (nice for arbitrary cache content)
            @param use_encode: if data should be encoded/decoded (nice for readable cache files)
        """
        self.request = request
        self.key = key
        self.locking = do_locking
        self.use_pickle = use_pickle
        self.use_encode = use_encode
        self.arena_dir = get_arena_dir(request, arena, scope)
        if not os.path.exists(self.arena_dir):
            os.makedirs(self.arena_dir)
        self._fname = os.path.join(self.arena_dir, key)

        # used by file-like api:
        self._lock = None  # either a read or a write lock
        self._fileobj = None  # open cache file object
        self._tmp_fname = None  # name of temporary file (used for write)
        self._mode = None  # mode of open file object


    def _filename(self):
        # DEPRECATED - please use file-like api
        return self._fname

    def exists(self):
        return os.path.exists(self._fname)

    def mtime(self):
        # DEPRECATED for checking a changed on-disk cache, please use
        # self.uid() for this, see below
        try:
            return os.path.getmtime(self._fname)
        except (IOError, OSError):
            return 0

    def size(self):
        try:
            return os.path.getsize(self._fname)
        except (IOError, OSError):
            return 0

    def uid(self):
        """ Return a value that likely changes when the on-disk cache was updated.

            See docstring of MoinMoin.util.filesys.fuid for details.
        """
        return filesys.fuid(self._fname)

    def needsUpdate(self, filename, attachdir=None):
        # following code is not necessary. will trigger exception and give same result
        #if not self.exists():
        #    return 1

        try:
            ctime = os.path.getmtime(self._fname)
            ftime = os.path.getmtime(filename)
        except os.error:
            return 1

        needsupdate = ftime > ctime

        # if a page depends on the attachment dir, we check this, too:
        if not needsupdate and attachdir:
            try:
                ftime2 = os.path.getmtime(attachdir)
            except os.error:
                ftime2 = 0
            needsupdate = ftime2 > ctime

        return needsupdate

    def lock(self, mode, timeout=10.0):
        """
        acquire a lock for <mode> ("r" or "w").
        we just raise a CacheError if this doesn't work.

        Note:
         * .open() calls .lock(), .close() calls .unlock() if do_locking is True.
         * if you need to do a read-modify-write, you want to use a CacheEntry
           with do_locking=False and manually call .lock('w') and .unlock().
        """
        lock_dir = os.path.join(self.arena_dir, '__lock__')
        if 'r' in mode:
            _lock = lock.LazyReadLock(lock_dir, 60.0)
        elif 'w' in mode:
            _lock = lock.LazyWriteLock(lock_dir, 60.0)
        acquired = _lock.acquire(timeout)
        if acquired:
            self._lock = _lock
        else:
            self._lock = None
            err = "Can't acquire %s lock in %s" % (mode, lock_dir)
            logging.error(err)
            raise CacheError(err)

    def unlock(self):
        """
        release the lock.
        """
        if self._lock:
            self._lock.release()
            self._lock = None

    # file-like interface ----------------------------------------------------

    def open(self, filename=None, mode='r', bufsize=-1):
        """ open the cache for reading/writing

        Typical usage:
            try:
                cache.open('r')  # open file, create locks
                data = cache.read()
            finally:
                cache.close()  # important to close file and remove locks

        @param filename: must be None (default - automatically determine filename)
        @param mode: 'r' (read, default), 'w' (write)
                     Note: if mode does not include 'b' (binary), it will be
                           automatically changed to include 'b'.
        @param bufsize: size of read/write buffer (default: -1 meaning automatic)
        @return: None (the opened file object is kept in self._fileobj and used
                 implicitely by read/write/close functions of CacheEntry object.
        """
        assert self._fileobj is None, 'caching: trying to open an already opened cache'
        assert filename is None, 'caching: giving a filename is not supported (yet?)'
        assert 'r' in mode or 'w' in mode, 'caching: mode must contain "r" or "w"'

        if 'b' not in mode:
            mode += 'b'  # we want to use binary mode, ever!
        self._mode = mode  # for self.close()

        if self.locking:
            self.lock(mode)
        try:
            if 'r' in mode:
                filename = self._fname
                self._fileobj = open(filename, mode, bufsize)
            elif 'w' in mode:
                # we do not write content to old inode, but to a new file
                # so we don't need to lock when we just want to read the file
                # (at least on POSIX, this works)
                filename = None
                fd, filename = tempfile.mkstemp('.tmp', self.key, self.arena_dir)
                self._tmp_fname = filename
                self._fileobj = os.fdopen(fd, mode, bufsize)
        except IOError, err:
            if 'w' in mode:
                # IOerror for 'r' can be just a non-existing file, do not log that,
                # but if open fails for 'w', we likely have some bigger problem:
                logging.error(str(err))
            raise CacheError(str(err))

    def read(self, size=-1):
        """ read data from cache file

        @param size: how many bytes to read (default: -1 == everything)
        @return: read data (str)
        """
        return self._fileobj.read(size)

    def write(self, data):
        """ write data to cache file

        @param data: write data (str)
        """
        self._fileobj.write(data)

    def close(self):
        """ close cache file (and release lock, if any) """
        try:
            if self._fileobj:
                self._fileobj.close()
                self._fileobj = None
                if 'w' in self._mode:
                    filesys.chmod(self._tmp_fname, 0666 & config.umask) # fix mode that mkstemp chose
                    # this is either atomic or happening with real locks set:
                    filesys.rename(self._tmp_fname, self._fname)
        finally:
            if self.locking:
                self.unlock()

    # ------------------------------------------------------------------------

    def update(self, content):
        try:
            if hasattr(content, 'read'):
                # content is file-like
                assert not (self.use_pickle or self.use_encode), 'caching: use_pickle and use_encode not supported with file-like api'
                try:
                    self.open(mode='w')
                    shutil.copyfileobj(content, self)
                finally:
                    self.close()
            else:
                # content is a string
                if self.use_pickle:
                    content = pickle.dumps(content, PICKLE_PROTOCOL)
                elif self.use_encode:
                    content = content.encode(config.charset)

                try:
                    self.open(mode='w')
                    self.write(content)
                finally:
                    self.close()
        except (pickle.PicklingError, OSError, IOError, ValueError), err:
            raise CacheError(str(err))

    def content(self):
        # no file-like api yet, we implement it when we need it
        try:
            try:
                self.open(mode='r')
                data = self.read()
            finally:
                self.close()
            if self.use_pickle:
                data = pickle.loads(data)
            elif self.use_encode:
                data = data.decode(config.charset)
            return data
        except (pickle.UnpicklingError, IOError, EOFError, ValueError), err:
            raise CacheError(str(err))

    def remove(self):
        if self.locking:
            self.lock('w')
        try:
            try:
                os.remove(self._fname)
            except OSError:
                pass
        finally:
            if self.locking:
                self.unlock()