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Viewing changes to bzrlib/trace.py

updated log file creation to avoid race based on implementation by Martin [gz]
https://code.launchpad.net/~parthm/bzr/no-chown-if-bzrlog-exists/+merge/22197

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bzrlib/trace.py
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    This sets the global _bzr_log_filename.
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    """
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    global _bzr_log_filename
 
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    def create_log_file(filename):
 
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        """Create a log file in while avoiding race.
 
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        """
 
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        buffering = 0 # unbuffered
 
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        mode = os.O_WRONLY | os.O_APPEND | osutils.O_TEXT
 
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        try:
 
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            fd = os.open(filename, mode)
 
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            logfile = os.fdopen(fd, 'at', buffering)
 
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            return logfile
 
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        except OSError, e:
 
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            if e.errno != errno.ENOENT:
 
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                raise
 
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        try:
 
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            fd = os.open(filename, mode | os.O_CREAT | os.O_EXCL)
 
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            logfile = os.fdopen(fd, 'at', buffering)
 
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        except OSError, e:
 
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            if e.errno != errno.EEXIST:
 
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                raise
 
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        else:
 
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            # Copy ownership from parent directory
 
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            osutils.copy_ownership(filename)
 
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            return logfile
 
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    _bzr_log_filename = _get_bzr_log_filename()
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    _rollover_trace_maybe(_bzr_log_filename)
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    try:
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        buffering = 0 # unbuffered
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        if os.path.exists(_bzr_log_filename):
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            bzr_log_file = open(_bzr_log_filename, 'at', buffering=buffering)
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        else:
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            # create log file with ownership of containing directory
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            bzr_log_file = osutils.open_with_ownership(_bzr_log_filename,
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                'at', buffering)
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        # bzr_log_file.tell() on windows always return 0 until some writing done
 
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        bzr_log_file = create_log_file(_bzr_log_filename)
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        bzr_log_file.write('\n')
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        if bzr_log_file.tell() <= 2:
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            bzr_log_file.write("this is a debug log for diagnosing/reporting problems in bzr\n")