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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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4
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import psutil |
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5
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import logging |
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6
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import errno |
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7
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8
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from contextlib import contextmanager |
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9
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10
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# Constants needed for `open_with_dirlock` function. |
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11
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MAX_ATTEMPTS = 1000 # This would correspond to be blocked for ~15min. |
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12
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TIME_BETWEEN_ATTEMPTS = 2 # In seconds |
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13
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14
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15
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def find_mount_point(path='.'): |
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16
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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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22
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23
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24
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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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26
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mount = find_mount_point(path) |
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27
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28
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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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31
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32
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33
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@contextmanager |
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34
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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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36
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f = open(*args, **kwargs) |
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37
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try: |
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38
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fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB) |
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39
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except IOError: |
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40
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no_attempt = 0 |
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41
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while no_attempt < MAX_ATTEMPTS: |
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42
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try: |
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43
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logging.info("Can't immediately write-lock the file ({0}), waiting.".format(f.name)) |
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44
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start_time = time.time() |
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45
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fcntl.lockf(f, fcntl.LOCK_EX) |
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46
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break |
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47
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except IOError as e: |
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48
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if e.errno == errno.EDEADLK: |
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49
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logging.warn("The OS complained because the process have been waiting on the lockf for {0} sec with the error ({1}: {2}). Retrying. ".format(time.time() - start_time), e.errno, e.strerror) |
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50
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no_attempt += 1 |
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51
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else: |
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52
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raise e |
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53
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54
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if no_attempt == MAX_ATTEMPTS: |
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55
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raise IOError("Failed to lock {0} {1} times.".format(f.name, MAX_ATTEMPTS)) |
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56
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57
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try: |
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yield f |
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59
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finally: |
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60
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fcntl.lockf(f, fcntl.LOCK_UN) |
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61
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f.close() |
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62
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63
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64
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@contextmanager |
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65
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def open_with_dirlock(*args, **kwargs): |
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66
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""" Context manager for opening file with an exclusive lock using. """ |
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67
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dirname = os.path.dirname(args[0]) |
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68
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filename = os.path.basename(args[0]) |
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69
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lockfile = os.path.join(dirname, "." + filename) |
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70
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71
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no_attempt = 0 |
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72
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while no_attempt < MAX_ATTEMPTS: |
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73
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try: |
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74
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os.mkdir(lockfile) # Atomic operation |
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75
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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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79
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no_attempt += 1 |
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80
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81
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if no_attempt == MAX_ATTEMPTS: |
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82
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raise IOError("Failed to lock {0} {1} times.".format(filename, MAX_ATTEMPTS)) |
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83
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84
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try: |
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85
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with open(*args, **kwargs) as f: |
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86
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yield f |
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87
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finally: |
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88
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os.rmdir(lockfile) |
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89
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90
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91
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def _fs_support_globalflock(fs): |
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92
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if fs.fstype == "lustre": |
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93
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return ("flock" in fs.opts) and "localflock" not in fs.opts |
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94
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95
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elif fs.fstype == "gpfs": |
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96
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return True |
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97
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98
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return False # We don't know. |
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99
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100
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101
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# Determine if we can rely on the fcntl module for locking files on the cluster. |
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102
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# Otherwise, fallback on using the directory creation atomicity as a locking mechanism. |
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103
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fs = get_fs('.') |
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104
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if _fs_support_globalflock(fs): |
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105
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open_with_lock = open_with_flock |
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106
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else: |
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107
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logging.warn("Cluster does not support flock! Falling back to folder lock.") |
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108
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open_with_lock = open_with_dirlock |
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109
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SMART-Lab /
smartdispatch
