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#!/usr/bin/env python
# BSD Licensed, Copyright (c) 2006-2008 MetaCarta, Inc.
"""This is intended to be run as a command line tool. Use --help to determine
arguments to this program. It is a tool to keep a certain directory
to a maximum size by removing least recently accessed files from the
import sys, os, heapq, time
from optparse import OptionParser
MAX_HEAP_SIZE = 1000000
def walk_disk_cache (rootdir, max_entries):
"""Walk a directory structure, building a heap of up to max_entries."""
heap = []
cache_size = 0
start = time.time()
for root, dirs, files in os.walk(rootdir):
for file in files:
path = os.path.join(root, file)
stat = os.stat(path)
size = stat.st_size
if hasattr(stat, 'st_blocks'):
size = stat.st_blocks * stat.st_blksize
# strip off rootdir to keep RAM use down
path = path[len(rootdir):]
heapq.heappush(heap, (stat.st_atime, size, path))
cache_size += size
del heap[max_entries:]
return heap, cache_size
def clean_disk_cache (rootdir, max_size, max_entries):
"""Remove files from directory until its size is less than max_size (which
is megabytes). Up to max_entries will be removed per-run."""
heap, cache_size = walk_disk_cache(rootdir, max_entries)
max_size <<= 20 # megabytes
print "Cache entries found: %d" % len(heap)
removed_files = 0
while heap and cache_size > max_size:
atime, size, path = heapq.heappop(heap)
cache_size -= size
path = rootdir + path
removed_files += 1
except OSError, e:
print >>sys.stderr, "Error removing tile %s: %s" % (path, e)
print "Removed %d files." % removed_files
if __name__ == "__main__":
usage = "usage: %prog [options] <cache_location>"
parser = OptionParser(usage=usage, version="%prog 1.0")
parser.add_option("-s", "--size", action="store", type="int",
dest="size", default = MAX_CACHE_SIZE,
help="Maximum cache size, in megabytes.")
parser.add_option("-e", "--entries", action="store", type="int",
dest="entries", default=MAX_HEAP_SIZE,
help="""Maximum cache entries. This limits the
amount of memory that will be used to store
information about tiles to remove.""")
(options, args) = parser.parse_args()
if not len(args):
parser.error("Missing required cache_location argument.")
clean_disk_cache(args[0], options.size, options.entries)
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