cacheblock_suffix = ".keepcacheblock"
class DiskCacheSlot(object):
- __slots__ = ("locator", "ready", "content", "cachedir")
+ __slots__ = ("locator", "ready", "content", "cachedir", "filehandle")
def __init__(self, locator, cachedir):
self.locator = locator
self.ready = threading.Event()
self.content = None
self.cachedir = cachedir
+ self.filehandle = None
def get(self):
self.ready.wait()
final = os.path.join(blockdir, self.locator) + cacheblock_suffix
- f = tempfile.NamedTemporaryFile(dir=blockdir, delete=False, prefix="tmp", suffix=cacheblock_suffix)
- tmpfile = f.name
+ self.filehandle = tempfile.NamedTemporaryFile(dir=blockdir, delete=False, prefix="tmp", suffix=cacheblock_suffix)
+ tmpfile = self.filehandle.name
os.chmod(tmpfile, stat.S_IRUSR | stat.S_IWUSR)
# aquire a shared lock, this tells other processes that
# we're using this block and to please not delete it.
- fcntl.flock(f, fcntl.LOCK_SH)
+ fcntl.flock(self.filehandle, fcntl.LOCK_SH)
- f.write(value)
- f.flush()
+ self.filehandle.write(value)
+ self.filehandle.flush()
os.rename(tmpfile, final)
tmpfile = None
- self.content = mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ)
- except OSError as e:
- if e.errno == errno.ENODEV:
- _logger.error("Unable to use disk cache: The underlying filesystem does not support memory mapping.")
- elif e.errno == errno.ENOMEM:
- _logger.error("Unable to use disk cache: The process's maximum number of mappings would have been exceeded.")
- elif e.errno == errno.ENOSPC:
- _logger.error("Unable to use disk cache: Out of disk space.")
- else:
- traceback.print_exc()
- except Exception as e:
- traceback.print_exc()
+ self.content = mmap.mmap(self.filehandle.fileno(), 0, access=mmap.ACCESS_READ)
finally:
if tmpfile is not None:
# If the tempfile hasn't been renamed on disk yet, try to delete it.
os.remove(tmpfile)
except:
pass
- if self.content is None:
- # Something went wrong with the disk cache, fall back
- # to RAM cache behavior (the alternative is to cache
- # nothing and return a read error).
- self.content = value
- self.ready.set()
def size(self):
if self.content is None:
blockdir = os.path.join(self.cachedir, self.locator[0:3])
final = os.path.join(blockdir, self.locator) + cacheblock_suffix
try:
- with open(final, "rb") as f:
- # unlock
- fcntl.flock(f, fcntl.LOCK_UN)
- self.content = None
-
- # try to get an exclusive lock, this ensures other
- # processes are not using the block. It is
- # nonblocking and will throw an exception if we
- # can't get it, which is fine because that means
- # we just won't try to delete it.
- #
- # I should note here, the file locking is not
- # strictly necessary, we could just remove it and
- # the kernel would ensure that the underlying
- # inode remains available as long as other
- # processes still have the file open. However, if
- # you have multiple processes sharing the cache
- # and deleting each other's files, you'll end up
- # with a bunch of ghost files that don't show up
- # in the file system but are still taking up
- # space, which isn't particularly user friendly.
- # The locking strategy ensures that cache blocks
- # in use remain visible.
- #
- fcntl.flock(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
-
- os.remove(final)
- return True
+ fcntl.flock(self.filehandle, fcntl.LOCK_UN)
+
+ # try to get an exclusive lock, this ensures other
+ # processes are not using the block. It is
+ # nonblocking and will throw an exception if we
+ # can't get it, which is fine because that means
+ # we just won't try to delete it.
+ #
+ # I should note here, the file locking is not
+ # strictly necessary, we could just remove it and
+ # the kernel would ensure that the underlying
+ # inode remains available as long as other
+ # processes still have the file open. However, if
+ # you have multiple processes sharing the cache
+ # and deleting each other's files, you'll end up
+ # with a bunch of ghost files that don't show up
+ # in the file system but are still taking up
+ # space, which isn't particularly user friendly.
+ # The locking strategy ensures that cache blocks
+ # in use remain visible.
+ #
+ fcntl.flock(self.filehandle, fcntl.LOCK_EX | fcntl.LOCK_NB)
+
+ os.remove(final)
+ return True
except OSError:
pass
+ finally:
+ self.filehandle = None
+ self.content = None
return False
@staticmethod
content = mmap.mmap(filehandle.fileno(), 0, access=mmap.ACCESS_READ)
dc = DiskCacheSlot(locator, cachedir)
+ dc.filehandle = filehandle
dc.content = content
dc.ready.set()
return dc
return None
+ @staticmethod
+ def cache_usage(cachedir):
+ usage = 0
+ for root, dirs, files in os.walk(cachedir):
+ for name in files:
+ if not name.endswith(cacheblock_suffix):
+ continue
+
+ blockpath = os.path.join(root, name)
+ res = os.stat(blockpath)
+ usage += res.st_size
+ return usage
+
+
@staticmethod
def init_cache(cachedir, maxslots):
+ #
+ # First check the disk cache works at all by creating a 1 byte cache entry
+ #
+ checkexists = DiskCacheSlot.get_from_disk('0cc175b9c0f1b6a831c399e269772661', cachedir)
+ ds = DiskCacheSlot('0cc175b9c0f1b6a831c399e269772661', cachedir)
+ ds.set(b'a')
+ if checkexists is None:
+ # Don't keep the test entry around unless it existed beforehand.
+ ds.evict()
+
# map in all the files in the cache directory, up to max slots.
# after max slots, try to delete the excess blocks.
#
projects / arvados.git / blobdiff