borg/dedupestore/cache.py

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import hashlib
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import logging
import msgpack
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import os
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import zlib
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from .helpers import pack, unpack
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NS_ARCHIVES = 'A'
NS_CHUNKS = 'C'
NS_CINDEX = 'I'
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class Cache(object):
"""Client Side cache
"""
def __init__(self, store):
self.store = store
self.path = os.path.join(os.path.expanduser('~'), '.dedupestore', 'cache',
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'%s.cache' % self.store.uuid)
self.tid = -1
self.open()
if self.tid != self.store.tid:
self.init()
def open(self):
if not os.path.exists(self.path):
return
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data = open(self.path, 'rb').read()
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cache = unpack(data)
version = cache.get('version')
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if version != 1:
logging.error('Unsupported cache version %r' % version)
return
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if cache['store'] != self.store.uuid:
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raise Exception('Cache UUID mismatch')
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self.chunkmap = cache['chunkmap']
self.tid = cache['tid']
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def init(self):
"""Initializes cache by fetching and reading all archive indicies
"""
logging.info('Initializing cache...')
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self.chunkmap = {}
self.tid = self.store.tid
if self.store.tid == 0:
return
for id in list(self.store.list(NS_CINDEX)):
cindex = unpack(self.store.get(NS_CINDEX, id))
for id, size in cindex['chunks']:
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try:
count, size = self.chunkmap[id]
self.chunkmap[id] = count + 1, size
except KeyError:
self.chunkmap[id] = 1, size
self.save()
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def save(self):
assert self.store.state == self.store.OPEN
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cache = {'version': 1,
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'store': self.store.uuid,
'chunkmap': self.chunkmap,
'tid': self.store.tid,
}
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_, data = pack(cache)
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cachedir = os.path.dirname(self.path)
if not os.path.exists(cachedir):
os.makedirs(cachedir)
with open(self.path, 'wb') as fd:
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fd.write(data)
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def add_chunk(self, id, data):
if self.seen_chunk(id):
return self.chunk_incref(id)
_, data = pack(data)
csize = len(data)
self.store.put(NS_CHUNKS, id, data)
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self.chunkmap[id] = (1, csize)
return csize
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def seen_chunk(self, id):
count, size = self.chunkmap.get(id, (0, 0))
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return count
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def chunk_incref(self, id):
count, size = self.chunkmap[id]
self.chunkmap[id] = (count + 1, size)
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return size
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def chunk_decref(self, id):
count, size = self.chunkmap[id]
if count == 1:
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del self.chunkmap[id]
self.store.delete(NS_CHUNKS, id)
else:
self.chunkmap[id] = (count - 1, size)