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import os |
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2
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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 logging |
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5
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6
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from contextlib import contextmanager |
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7
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8
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have_psutil = True |
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9
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try: |
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10
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import psutil |
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11
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except ImportError: |
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12
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have_psutil = False |
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13
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14
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# Constants needed for `open_with_dirlock` function. |
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15
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MAX_ATTEMPTS = 1000 # This would correspond to be blocked for ~15min. |
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16
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TIME_BETWEEN_ATTEMPTS = 1 # In seconds |
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17
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18
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19
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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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22
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while not os.path.ismount(path): |
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path = os.path.dirname(path) |
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25
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return path |
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26
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27
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28
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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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30
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mount = find_mount_point(path) |
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31
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32
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for fs in psutil.disk_partitions(True): |
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33
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if fs.mountpoint == mount: |
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return fs |
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35
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36
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37
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@contextmanager |
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def open_with_flock(*args, **kwargs): |
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39
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""" Context manager for opening file with an exclusive lock. """ |
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40
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f = open(*args, **kwargs) |
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41
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try: |
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42
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fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB) |
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43
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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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45
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fcntl.lockf(f, fcntl.LOCK_EX) |
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46
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47
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yield f |
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48
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fcntl.lockf(f, fcntl.LOCK_UN) |
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49
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f.close() |
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50
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51
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52
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@contextmanager |
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53
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def open_with_dirlock(*args, **kwargs): |
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54
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""" Context manager for opening file with an exclusive lock using. """ |
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55
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dirname = os.path.dirname(args[0]) |
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56
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filename = os.path.basename(args[0]) |
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57
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lockfile = os.path.join(dirname, "." + filename) |
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58
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59
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no_attempt = 0 |
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60
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while no_attempt < MAX_ATTEMPTS: |
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61
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try: |
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62
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os.mkdir(lockfile) # Atomic operation |
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63
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f = open(*args, **kwargs) |
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64
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yield f |
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65
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f.close() |
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66
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os.rmdir(lockfile) |
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67
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break |
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68
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except OSError: |
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69
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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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70
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time.sleep(TIME_BETWEEN_ATTEMPTS) |
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71
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no_attempt += 1 |
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72
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73
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74
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# Determine if we can rely on the fcntl module for locking files on the cluster. |
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75
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# Otherwise, fallback on using the directory creation atomicity as a locking mechanism. |
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76
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open_with_lock = open_with_dirlock |
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77
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if have_psutil: |
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78
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fs = get_fs('.') |
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79
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if fs.fstype == "lustre" and "localflock" not in fs.opts: |
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80
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print("Cluster supports flock.") |
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81
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open_with_lock = open_with_flock |
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82
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SMART-Lab /
smartdispatch
