/usr/lib/python2.7/dist-packages/fs/remote.py is in python-fs 0.4.0-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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fs.remote
=========
Utilities for interfacing with remote filesystems
This module provides reusable utility functions that can be used to construct
FS subclasses interfacing with a remote filesystem. These include:
* RemoteFileBuffer: a file-like object that locally buffers the contents of
a remote file, writing them back on flush() or close().
* ConnectionManagerFS: a WrapFS subclass that tracks the connection state
of a remote FS, and allows client code to wait for
a connection to be re-established.
* CacheFS: a WrapFS subclass that caches file and directory meta-data in
memory, to speed access to a remote FS.
"""
from __future__ import with_statement
import time
import stat as statinfo
from errno import EINVAL
import fs.utils
from fs.base import threading, FS
from fs.wrapfs import WrapFS, wrap_fs_methods
from fs.wrapfs.lazyfs import LazyFS
from fs.path import *
from fs.errors import *
from fs.local_functools import wraps
from fs.filelike import StringIO, SpooledTemporaryFile, FileWrapper
from fs import SEEK_SET, SEEK_CUR, SEEK_END
_SENTINAL = object()
class RemoteFileBuffer(FileWrapper):
"""File-like object providing buffer for local file operations.
Instances of this class manage a local tempfile buffer corresponding
to the contents of a remote file. All reads and writes happen locally,
with the content being copied to the remote file only on flush() or
close(). Writes to the remote file are performed using the setcontents()
method on the owning FS object.
The intended use-case is for a remote filesystem (e.g. S3FS) to return
instances of this class from its open() method, and to provide the
file-uploading logic in its setcontents() method, as in the following
pseudo-code::
def open(self,path,mode="r"):
rf = self._get_remote_file(path)
return RemoteFileBuffer(self,path,mode,rf)
def setcontents(self,path,file):
self._put_remote_file(path,file)
The contents of the remote file are read into the buffer on-demand.
"""
max_size_in_memory = 1024 * 8
def __init__(self, fs, path, mode, rfile=None, write_on_flush=True):
"""RemoteFileBuffer constructor.
The owning filesystem, path and mode must be provided. If the
optional argument 'rfile' is provided, it must be a read()-able
object or a string containing the initial file contents.
"""
wrapped_file = SpooledTemporaryFile(max_size=self.max_size_in_memory)
self.fs = fs
self.path = path
self.write_on_flush = write_on_flush
self._changed = False
self._readlen = 0 # How many bytes already loaded from rfile
self._rfile = None # Reference to remote file object
self._eof = False # Reached end of rfile?
if getattr(fs,"_lock",None) is not None:
self._lock = fs._lock.__class__()
else:
self._lock = threading.RLock()
if "r" in mode or "+" in mode or "a" in mode:
if rfile is None:
# File was just created, force to write anything
self._changed = True
self._eof = True
if not hasattr(rfile, "read"):
rfile = StringIO(unicode(rfile))
self._rfile = rfile
else:
# Do not use remote file object
self._eof = True
self._rfile = None
if rfile is not None and hasattr(rfile,"close"):
rfile.close()
super(RemoteFileBuffer,self).__init__(wrapped_file,mode)
# FIXME: What if mode with position on eof?
if "a" in mode:
# Not good enough...
self.seek(0, SEEK_END)
def __del__(self):
# Don't try to close a partially-constructed file
if "_lock" in self.__dict__:
if not self.closed:
try:
self.close()
except FSError:
pass
def _write(self,data,flushing=False):
with self._lock:
# Do we need to discard info from the buffer?
toread = len(data) - (self._readlen - self.wrapped_file.tell())
if toread > 0:
if not self._eof:
self._fillbuffer(toread)
else:
self._readlen += toread
self._changed = True
self.wrapped_file.write(data)
def _read_remote(self, length=None):
"""Read data from the remote file into the local buffer."""
chunklen = 1024 * 256
bytes_read = 0
while True:
toread = chunklen
if length is not None and length - bytes_read < chunklen:
toread = length - bytes_read
if not toread:
break
data = self._rfile.read(toread)
datalen = len(data)
if not datalen:
self._eof = True
break
bytes_read += datalen
self.wrapped_file.write(data)
if datalen < toread:
# We reached EOF,
# no more reads needed
self._eof = True
break
if self._eof and self._rfile is not None:
self._rfile.close()
self._readlen += bytes_read
def _fillbuffer(self, length=None):
"""Fill the local buffer, leaving file position unchanged.
This method is used for on-demand loading of data from the remote file
into the buffer. It reads 'length' bytes from rfile and writes them
into the buffer, seeking back to the original file position.
"""
curpos = self.wrapped_file.tell()
if length == None:
if not self._eof:
# Read all data and we didn't reached EOF
# Merge endpos - tell + bytes from rfile
self.wrapped_file.seek(0, SEEK_END)
self._read_remote()
self._eof = True
self.wrapped_file.seek(curpos)
elif not self._eof:
if curpos + length > self._readlen:
# Read all data and we didn't reached EOF
# Load endpos - tell() + len bytes from rfile
toload = length - (self._readlen - curpos)
self.wrapped_file.seek(0, SEEK_END)
self._read_remote(toload)
self.wrapped_file.seek(curpos)
def _read(self, length=None):
if length < 0:
length = None
with self._lock:
self._fillbuffer(length)
data = self.wrapped_file.read(length if length != None else -1)
if not data:
data = None
return data
def _seek(self,offset,whence=SEEK_SET):
with self._lock:
if not self._eof:
# Count absolute position of seeking
if whence == SEEK_SET:
abspos = offset
elif whence == SEEK_CUR:
abspos = offset + self.wrapped_file.tell()
elif whence == SEEK_END:
abspos = None
else:
raise IOError(EINVAL, 'Invalid whence')
if abspos != None:
toread = abspos - self._readlen
if toread > 0:
self.wrapped_file.seek(self._readlen)
self._fillbuffer(toread)
else:
self.wrapped_file.seek(self._readlen)
self._fillbuffer()
self.wrapped_file.seek(offset, whence)
def _truncate(self,size):
with self._lock:
if not self._eof and self._readlen < size:
# Read the rest of file
self._fillbuffer(size - self._readlen)
# Lock rfile
self._eof = True
elif self._readlen >= size:
# Crop rfile metadata
self._readlen = size if size != None else 0
# Lock rfile
self._eof = True
self.wrapped_file.truncate(size)
self._changed = True
self.flush()
if self._rfile is not None:
self._rfile.close()
def flush(self):
with self._lock:
self.wrapped_file.flush()
if self.write_on_flush:
self._setcontents()
def _setcontents(self):
if not self._changed:
# Nothing changed, no need to write data back
return
# If not all data loaded, load until eof
if not self._eof:
self._fillbuffer()
if "w" in self.mode or "a" in self.mode or "+" in self.mode:
pos = self.wrapped_file.tell()
self.wrapped_file.seek(0)
self.fs.setcontents(self.path, self.wrapped_file)
self.wrapped_file.seek(pos)
def close(self):
with self._lock:
if not self.closed:
self._setcontents()
if self._rfile is not None:
self._rfile.close()
super(RemoteFileBuffer,self).close()
class ConnectionManagerFS(LazyFS):
"""FS wrapper providing simple connection management of a remote FS.
The ConnectionManagerFS class is designed to wrap a remote FS object
and provide some convenience methods for dealing with its remote
connection state.
The boolean attribute 'connected' indicates whether the remote filesystem
has an active connection, and is initially True. If any of the remote
filesystem methods raises a RemoteConnectionError, 'connected' will
switch to False and remain so until a successful remote method call.
Application code can use the method 'wait_for_connection' to block
until the connection is re-established. Currently this reconnection
is checked by a simple polling loop; eventually more sophisticated
operating-system integration may be added.
Since some remote FS classes can raise RemoteConnectionError during
initialization, this class makes use of lazy initialization. The
remote FS can be specified as an FS instance, an FS subclass, or a
(class,args) or (class,args,kwds) tuple. For example::
>>> fs = ConnectionManagerFS(MyRemoteFS("http://www.example.com/"))
Traceback (most recent call last):
...
RemoteConnectionError: couldn't connect to "http://www.example.com/"
>>> fs = ConnectionManagerFS((MyRemoteFS,["http://www.example.com/"]))
>>> fs.connected
False
>>>
"""
poll_interval = 1
def __init__(self,wrapped_fs,poll_interval=None,connected=True):
super(ConnectionManagerFS,self).__init__(wrapped_fs)
if poll_interval is not None:
self.poll_interval = poll_interval
self._connection_cond = threading.Condition()
self._poll_thread = None
self._poll_sleeper = threading.Event()
self.connected = connected
def setcontents(self, path, data, chunk_size=64*1024):
return self.wrapped_fs.setcontents(path, data, chunk_size=chunk_size)
def __getstate__(self):
state = super(ConnectionManagerFS,self).__getstate__()
del state["_connection_cond"]
del state["_poll_sleeper"]
state["_poll_thread"] = None
return state
def __setstate__(self,state):
super(ConnectionManagerFS,self).__setstate__(state)
self._connection_cond = threading.Condition()
self._poll_sleeper = threading.Event()
def wait_for_connection(self,timeout=None,force_wait=False):
self._connection_cond.acquire()
try:
if force_wait:
self.connected = False
if not self.connected:
if not self._poll_thread:
target = self._poll_connection
self._poll_thread = threading.Thread(target=target)
self._poll_thread.daemon = True
self._poll_thread.start()
self._connection_cond.wait(timeout)
finally:
self._connection_cond.release()
def _poll_connection(self):
while not self.connected and not self.closed:
try:
self.wrapped_fs.getinfo("/")
except RemoteConnectionError:
self._poll_sleeper.wait(self.poll_interval)
self._poll_sleeper.clear()
except FSError:
break
else:
break
self._connection_cond.acquire()
try:
if not self.closed:
self.connected = True
self._poll_thread = None
self._connection_cond.notifyAll()
finally:
self._connection_cond.release()
def close(self):
if not self.closed:
try:
super(ConnectionManagerFS,self).close()
except (RemoteConnectionError,):
pass
if self._poll_thread:
self.connected = True
self._poll_sleeper.set()
self._poll_thread.join()
self._poll_thread = None
def _ConnectionManagerFS_method_wrapper(func):
"""Method wrapper for ConnectionManagerFS.
This method wrapper keeps an eye out for RemoteConnectionErrors and
adjusts self.connected accordingly.
"""
@wraps(func)
def wrapper(self,*args,**kwds):
try:
result = func(self,*args,**kwds)
except RemoteConnectionError:
self.connected = False
raise
except FSError:
self.connected = True
raise
else:
self.connected = True
return result
return wrapper
wrap_fs_methods(_ConnectionManagerFS_method_wrapper,ConnectionManagerFS)
class CachedInfo(object):
"""Info objects stored in cache for CacheFS."""
__slots__ = ("timestamp","info","has_full_info","has_full_children")
def __init__(self,info={},has_full_info=True,has_full_children=False):
self.timestamp = time.time()
self.info = info
self.has_full_info = has_full_info
self.has_full_children = has_full_children
def clone(self):
new_ci = self.__class__()
new_ci.update_from(self)
return new_ci
def update_from(self,other):
self.timestamp = other.timestamp
self.info = other.info
self.has_full_info = other.has_full_info
self.has_full_children = other.has_full_children
@classmethod
def new_file_stub(cls):
info = {"info" : 0700 | statinfo.S_IFREG}
return cls(info,has_full_info=False)
@classmethod
def new_dir_stub(cls):
info = {"info" : 0700 | statinfo.S_IFDIR}
return cls(info,has_full_info=False)
class CacheFSMixin(FS):
"""Simple FS mixin to cache meta-data of a remote filesystems.
This FS mixin implements a simplistic cache that can help speed up
access to a remote filesystem. File and directory meta-data is cached
but the actual file contents are not.
If you want to add caching to an existing FS object, use the CacheFS
class instead; it's an easy-to-use wrapper rather than a mixin.
This mixin class is provided for FS implementors who want to use
caching internally in their own classes.
FYI, the implementation of CacheFS is this:
class CacheFS(CacheFSMixin,WrapFS):
pass
"""
def __init__(self,*args,**kwds):
"""CacheFSMixin constructor.
The optional keyword argument 'cache_timeout' specifies the cache
timeout in seconds. The default timeout is 1 second. To prevent
cache entries from ever timing out, set it to None.
The optional keyword argument 'max_cache_size' specifies the maximum
number of entries to keep in the cache. To allow the cache to grow
without bound, set it to None. The default is 1000.
"""
self.cache_timeout = kwds.pop("cache_timeout",1)
self.max_cache_size = kwds.pop("max_cache_size",1000)
self.__cache = PathMap()
self.__cache_size = 0
self.__cache_lock = threading.RLock()
super(CacheFSMixin,self).__init__(*args,**kwds)
def clear_cache(self,path=""):
with self.__cache_lock:
self.__cache.clear(path)
try:
scc = super(CacheFSMixin,self).clear_cache
except AttributeError:
pass
else:
scc()
def __getstate__(self):
state = super(CacheFSMixin,self).__getstate__()
state.pop("_CacheFSMixin__cache",None)
state.pop("_CacheFSMixin__cache_size",None)
state.pop("_CacheFSMixin__cache_lock",None)
return state
def __setstate__(self,state):
super(CacheFSMixin,self).__setstate__(state)
self.__cache = PathMap()
self.__cache_size = 0
self.__cache_lock = threading.RLock()
def __get_cached_info(self,path,default=_SENTINAL):
try:
info = self.__cache[path]
if self.cache_timeout is not None:
now = time.time()
if info.timestamp < (now - self.cache_timeout):
with self.__cache_lock:
self.__expire_from_cache(path)
raise KeyError
return info
except KeyError:
if default is not _SENTINAL:
return default
raise
def __set_cached_info(self,path,new_ci,old_ci=None):
was_room = True
with self.__cache_lock:
# Free up some room in the cache
if self.max_cache_size is not None and old_ci is None:
while self.__cache_size >= self.max_cache_size:
try:
to_del = iter(self.__cache).next()
except StopIteration:
break
else:
was_room = False
self.__expire_from_cache(to_del)
# Atomically add to the cache.
# If there's a race, newest information wins
ci = self.__cache.setdefault(path,new_ci)
if ci is new_ci:
self.__cache_size += 1
else:
if old_ci is None or ci is old_ci:
if ci.timestamp < new_ci.timestamp:
ci.update_from(new_ci)
return was_room
def __expire_from_cache(self,path):
del self.__cache[path]
self.__cache_size -= 1
for ancestor in recursepath(path):
try:
self.__cache[ancestor].has_full_children = False
except KeyError:
pass
def open(self,path,mode="r",**kwds):
# Try to validate the entry using the cached info
try:
ci = self.__get_cached_info(path)
except KeyError:
if path in ("","/"):
raise ResourceInvalidError(path)
try:
ppath = dirname(path)
pci = self.__get_cached_info(ppath)
except KeyError:
pass
else:
if not fs.utils.isdir(super(CacheFSMixin,self),ppath,pci.info):
raise ResourceInvalidError(path)
if pci.has_full_children:
raise ResourceNotFoundError(path)
else:
if not fs.utils.isfile(super(CacheFSMixin,self),path,ci.info):
raise ResourceInvalidError(path)
f = super(CacheFSMixin,self).open(path,mode,**kwds)
if "w" in mode or "a" in mode or "+" in mode:
with self.__cache_lock:
self.__cache.clear(path)
f = self._CacheInvalidatingFile(self,path,f,mode)
return f
class _CacheInvalidatingFile(FileWrapper):
def __init__(self,owner,path,wrapped_file,mode=None):
self.path = path
sup = super(CacheFSMixin._CacheInvalidatingFile,self)
sup.__init__(wrapped_file,mode)
self.owner = owner
def _write(self,string,flushing=False):
with self.owner._CacheFSMixin__cache_lock:
self.owner._CacheFSMixin__cache.clear(self.path)
sup = super(CacheFSMixin._CacheInvalidatingFile,self)
return sup._write(string,flushing=flushing)
def _truncate(self,size):
with self.owner._CacheFSMixin__cache_lock:
self.owner._CacheFSMixin__cache.clear(self.path)
sup = super(CacheFSMixin._CacheInvalidatingFile,self)
return sup._truncate(size)
def exists(self,path):
try:
self.getinfo(path)
except ResourceNotFoundError:
return False
else:
return True
def isdir(self,path):
try:
self.__cache.iternames(path).next()
return True
except StopIteration:
pass
except RuntimeError:
pass
try:
info = self.getinfo(path)
except ResourceNotFoundError:
return False
else:
return fs.utils.isdir(super(CacheFSMixin,self),path,info)
def isfile(self,path):
try:
self.__cache.iternames(path).next()
return False
except StopIteration:
pass
except RuntimeError:
pass
try:
info = self.getinfo(path)
except ResourceNotFoundError:
return False
else:
return fs.utils.isfile(super(CacheFSMixin,self),path,info)
def getinfo(self,path):
try:
ci = self.__get_cached_info(path)
if not ci.has_full_info:
raise KeyError
info = ci.info
except KeyError:
info = super(CacheFSMixin,self).getinfo(path)
self.__set_cached_info(path,CachedInfo(info))
return info
def listdir(self,path="",*args,**kwds):
return list(nm for (nm, _info) in self.listdirinfo(path,*args,**kwds))
def ilistdir(self,path="",*args,**kwds):
for (nm, _info) in self.ilistdirinfo(path,*args,**kwds):
yield nm
def listdirinfo(self,path="",*args,**kwds):
items = super(CacheFSMixin,self).listdirinfo(path,*args,**kwds)
with self.__cache_lock:
names = set()
for (nm,info) in items:
names.add(basename(nm))
cpath = pathjoin(path,basename(nm))
ci = CachedInfo(info)
self.__set_cached_info(cpath,ci)
to_del = []
for nm in self.__cache.names(path):
if nm not in names:
to_del.append(nm)
for nm in to_del:
self.__cache.clear(pathjoin(path,nm))
#try:
# pci = self.__cache[path]
#except KeyError:
# pci = CachedInfo.new_dir_stub()
# self.__cache[path] = pci
#pci.has_full_children = True
return items
def ilistdirinfo(self,path="",*args,**kwds):
items = super(CacheFSMixin,self).ilistdirinfo(path,*args,**kwds)
for (nm,info) in items:
cpath = pathjoin(path,basename(nm))
ci = CachedInfo(info)
self.__set_cached_info(cpath,ci)
yield (nm,info)
def getsize(self,path):
return self.getinfo(path)["size"]
def setcontents(self, path, contents="", chunk_size=64*1024):
supsc = super(CacheFSMixin,self).setcontents
res = supsc(path, contents, chunk_size=chunk_size)
with self.__cache_lock:
self.__cache.clear(path)
self.__cache[path] = CachedInfo.new_file_stub()
return res
def createfile(self, path):
super(CacheFSMixin,self).createfile(path)
with self.__cache_lock:
self.__cache.clear(path)
self.__cache[path] = CachedInfo.new_file_stub()
def makedir(self,path,*args,**kwds):
super(CacheFSMixin,self).makedir(path,*args,**kwds)
with self.__cache_lock:
self.__cache.clear(path)
self.__cache[path] = CachedInfo.new_dir_stub()
def remove(self,path):
super(CacheFSMixin,self).remove(path)
with self.__cache_lock:
self.__cache.clear(path)
def removedir(self,path,**kwds):
super(CacheFSMixin,self).removedir(path,**kwds)
with self.__cache_lock:
self.__cache.clear(path)
def rename(self,src,dst):
super(CacheFSMixin,self).rename(src,dst)
with self.__cache_lock:
for (subpath,ci) in self.__cache.items(src):
self.__cache[pathjoin(dst,subpath)] = ci.clone()
self.__cache.clear(src)
def copy(self,src,dst,**kwds):
super(CacheFSMixin,self).copy(src,dst,**kwds)
with self.__cache_lock:
for (subpath,ci) in self.__cache.items(src):
self.__cache[pathjoin(dst,subpath)] = ci.clone()
def copydir(self,src,dst,**kwds):
super(CacheFSMixin,self).copydir(src,dst,**kwds)
with self.__cache_lock:
for (subpath,ci) in self.__cache.items(src):
self.__cache[pathjoin(dst,subpath)] = ci.clone()
def move(self,src,dst,**kwds):
super(CacheFSMixin,self).move(src,dst,**kwds)
with self.__cache_lock:
for (subpath,ci) in self.__cache.items(src):
self.__cache[pathjoin(dst,subpath)] = ci.clone()
self.__cache.clear(src)
def movedir(self,src,dst,**kwds):
super(CacheFSMixin,self).movedir(src,dst,**kwds)
with self.__cache_lock:
for (subpath,ci) in self.__cache.items(src):
self.__cache[pathjoin(dst,subpath)] = ci.clone()
self.__cache.clear(src)
def settimes(self,path,*args,**kwds):
super(CacheFSMixin,self).settimes(path,*args,**kwds)
with self.__cache_lock:
self.__cache.pop(path,None)
class CacheFS(CacheFSMixin,WrapFS):
"""Simple FS wrapper to cache meta-data of a remote filesystems.
This FS mixin implements a simplistic cache that can help speed up
access to a remote filesystem. File and directory meta-data is cached
but the actual file contents are not.
"""
pass
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