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import os |
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import time |
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3
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import fcntl |
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import psutil |
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import logging |
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7
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from contextlib import contextmanager |
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9
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# Constants needed for `open_with_dirlock` function. |
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MAX_ATTEMPTS = 1000 # This would correspond to be blocked for ~15min. |
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TIME_BETWEEN_ATTEMPTS = 1 # In seconds |
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def find_mount_point(path='.'): |
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""" Finds the mount point used to access `path`. """ |
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path = os.path.abspath(path) |
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while not os.path.ismount(path): |
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path = os.path.dirname(path) |
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return path |
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def get_fs(path='.'): |
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""" Gets info about the filesystem on which `path` lives. """ |
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mount = find_mount_point(path) |
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for fs in psutil.disk_partitions(True): |
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if fs.mountpoint == mount: |
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return fs |
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@contextmanager |
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def open_with_flock(*args, **kwargs): |
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""" Context manager for opening file with an exclusive lock. """ |
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f = open(*args, **kwargs) |
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try: |
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fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB) |
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except IOError: |
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logging.info("Can't immediately write-lock the file ({0}), waiting ...".format(f.name)) |
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fcntl.lockf(f, fcntl.LOCK_EX) |
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yield f |
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fcntl.lockf(f, fcntl.LOCK_UN) |
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f.close() |
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@contextmanager |
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def open_with_dirlock(*args, **kwargs): |
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""" Context manager for opening file with an exclusive lock using. """ |
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dirname = os.path.dirname(args[0]) |
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filename = os.path.basename(args[0]) |
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lockfile = os.path.join(dirname, "." + filename) |
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53
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54
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no_attempt = 0 |
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while no_attempt < MAX_ATTEMPTS: |
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try: |
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os.mkdir(lockfile) # Atomic operation |
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f = open(*args, **kwargs) |
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yield f |
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f.close() |
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os.rmdir(lockfile) |
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break |
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except OSError: |
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logging.info("Can't immediately write-lock the file ({0}), retrying in {1} sec. ...".format(filename, TIME_BETWEEN_ATTEMPTS)) |
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time.sleep(TIME_BETWEEN_ATTEMPTS) |
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no_attempt += 1 |
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68
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69
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def _fs_support_globalflock(fs): |
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if fs.fstype == "lustre": |
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return ("flock" in fs.opts) and "localflock" not in fs.opts |
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73
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elif fs.fstype == "gpfs": |
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return True |
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76
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return False # We don't know. |
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79
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# Determine if we can rely on the fcntl module for locking files on the cluster. |
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# Otherwise, fallback on using the directory creation atomicity as a locking mechanism. |
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fs = get_fs('.') |
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if _fs_support_globalflock(fs): |
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open_with_lock = open_with_flock |
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else: |
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logging.warn("Cluster does not support flock!") |
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open_with_lock = open_with_dirlock |
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SMART-Lab /
smartdispatch
