services/fuse/arvados_fuse/fusefile.py

   1 import json
   2 import llfuse
   3 import logging
   4 import re
   5 import time
   6
   7 from fresh import FreshBase, convertTime
   8
   9 _logger = logging.getLogger('arvados.arvados_fuse')
  10
  11 class File(FreshBase):
  12     """Base for file objects."""
  13
  14     def __init__(self, parent_inode, _mtime=0):
  15         super(File, self).__init__()
  16         self.inode = None
  17         self.parent_inode = parent_inode
  18         self._mtime = _mtime
  19
  20     def size(self):
  21         return 0
  22
  23     def readfrom(self, off, size, num_retries=0):
  24         return ''
  25
  26     def writeto(self, off, size, num_retries=0):
  27         raise Exception("Not writable")
  28
  29     def mtime(self):
  30         return self._mtime
  31
  32     def clear(self, force=False):
  33         return True
  34
  35     def writable(self):
  36         return False
  37
  38     def flush(self):
  39         pass
  40
  41
  42 class FuseArvadosFile(File):
  43     """Wraps a ArvadosFile."""
  44
  45     def __init__(self, parent_inode, arvfile, _mtime):
  46         super(FuseArvadosFile, self).__init__(parent_inode, _mtime)
  47         self.arvfile = arvfile
  48
  49     def size(self):
  50         with llfuse.lock_released:
  51             return self.arvfile.size()
  52
  53     def readfrom(self, off, size, num_retries=0):
  54         with llfuse.lock_released:
  55             return self.arvfile.readfrom(off, size, num_retries, exact=True)
  56
  57     def writeto(self, off, buf, num_retries=0):
  58         with llfuse.lock_released:
  59             return self.arvfile.writeto(off, buf, num_retries)
  60
  61     def stale(self):
  62         return False
  63
  64     def writable(self):
  65         return self.arvfile.writable()
  66
  67     def flush(self):
  68         with llfuse.lock_released:
  69             if self.writable():
  70                 self.arvfile.parent.root_collection().save()
  71
  72
  73 class StringFile(File):
  74     """Wrap a simple string as a file"""
  75     def __init__(self, parent_inode, contents, _mtime):
  76         super(StringFile, self).__init__(parent_inode, _mtime)
  77         self.contents = contents
  78
  79     def size(self):
  80         return len(self.contents)
  81
  82     def readfrom(self, off, size, num_retries=0):
  83         return self.contents[off:(off+size)]
  84
  85
  86 class ObjectFile(StringFile):
  87     """Wrap a dict as a serialized json object."""
  88
  89     def __init__(self, parent_inode, obj):
  90         super(ObjectFile, self).__init__(parent_inode, "", 0)
  91         self.object_uuid = obj['uuid']
  92         self.update(obj)
  93
  94     def uuid(self):
  95         return self.object_uuid
  96
  97     def update(self, obj=None):
  98         self._mtime = convertTime(obj['modified_at']) if 'modified_at' in obj else 0
  99         self.contents = json.dumps(obj, indent=4, sort_keys=True) + "\n"
 100
 101     def persisted(self):
 102         return True
 103
 104
 105 class FuncToJSONFile(StringFile):
 106     """File content is the return value of a given function, encoded as JSON.
 107
 108     The function is called at the time the file is read. The result is
 109     cached until invalidate() is called.
 110     """
 111     def __init__(self, parent_inode, func):
 112         super(FuncToJSONFile, self).__init__(parent_inode, "", 0)
 113         self.func = func
 114
 115         # invalidate_inode() and invalidate_entry() are asynchronous
 116         # with no callback to wait for. In order to guarantee
 117         # userspace programs don't get stale data that was generated
 118         # before the last invalidate(), we must disallow dirent
 119         # caching entirely.
 120         self.allow_dirent_cache = False
 121
 122     def size(self):
 123         self._update()
 124         return super(FuncToJSONFile, self).size()
 125
 126     def readfrom(self, *args, **kwargs):
 127         self._update()
 128         return super(FuncToJSONFile, self).readfrom(*args, **kwargs)
 129
 130     def _update(self):
 131         if not self.stale():
 132             return
 133         self._mtime = time.time()
 134         obj = self.func()
 135         self.contents = json.dumps(obj, indent=4, sort_keys=True) + "\n"
 136         self.fresh()