X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/2403cd9fd5a508252fe4570d6eed9c9c4efa366a..0e0cbc43912e4bd8ad3fda616e552380d61c3f8d:/services/fuse/arvados_fuse/fusefile.py

diff --git a/services/fuse/arvados_fuse/fusefile.py b/services/fuse/arvados_fuse/fusefile.py
index 77b70f5992..cedb4fb451 100644
--- a/services/fuse/arvados_fuse/fusefile.py
+++ b/services/fuse/arvados_fuse/fusefile.py
@@ -1,7 +1,12 @@
-import logging
-import re
+# Copyright (C) The Arvados Authors. All rights reserved.
+#
+# SPDX-License-Identifier: AGPL-3.0
+
 import json
 import llfuse
+import logging
+import re
+import time
 
 from fresh import FreshBase, convertTime
 
@@ -10,6 +15,8 @@ _logger = logging.getLogger('arvados.arvados_fuse')
 class File(FreshBase):
     """Base for file objects."""
 
+    __slots__ = ("inode", "parent_inode", "_mtime")
+
     def __init__(self, parent_inode, _mtime=0):
         super(File, self).__init__()
         self.inode = None
@@ -28,8 +35,8 @@ class File(FreshBase):
     def mtime(self):
         return self._mtime
 
-    def clear(self, force=False):
-        return True
+    def clear(self):
+        pass
 
     def writable(self):
         return False
@@ -37,21 +44,27 @@ class File(FreshBase):
     def flush(self):
         pass
 
+
 class FuseArvadosFile(File):
     """Wraps a ArvadosFile."""
 
+    __slots__ = ('arvfile',)
+
     def __init__(self, parent_inode, arvfile, _mtime):
         super(FuseArvadosFile, self).__init__(parent_inode, _mtime)
         self.arvfile = arvfile
 
     def size(self):
-        return self.arvfile.size()
+        with llfuse.lock_released:
+            return self.arvfile.size()
 
     def readfrom(self, off, size, num_retries=0):
-        return self.arvfile.readfrom(off, size, num_retries, exact=True)
+        with llfuse.lock_released:
+            return self.arvfile.readfrom(off, size, num_retries, exact=True)
 
     def writeto(self, off, buf, num_retries=0):
-        return self.arvfile.writeto(off, buf, num_retries)
+        with llfuse.lock_released:
+            return self.arvfile.writeto(off, buf, num_retries)
 
     def stale(self):
         return False
@@ -90,8 +103,47 @@ class ObjectFile(StringFile):
         return self.object_uuid
 
     def update(self, obj=None):
+        if obj is None:
+            # TODO: retrieve the current record for self.object_uuid
+            # from the server. For now, at least don't crash when
+            # someone tells us it's a good time to update but doesn't
+            # pass us a fresh obj. See #8345
+            return
         self._mtime = convertTime(obj['modified_at']) if 'modified_at' in obj else 0
         self.contents = json.dumps(obj, indent=4, sort_keys=True) + "\n"
 
     def persisted(self):
         return True
+
+
+class FuncToJSONFile(StringFile):
+    """File content is the return value of a given function, encoded as JSON.
+
+    The function is called at the time the file is read. The result is
+    cached until invalidate() is called.
+    """
+    def __init__(self, parent_inode, func):
+        super(FuncToJSONFile, self).__init__(parent_inode, "", 0)
+        self.func = func
+
+        # invalidate_inode() is asynchronous with no callback to wait for. In
+        # order to guarantee userspace programs don't get stale data that was
+        # generated before the last invalidate(), we must disallow inode
+        # caching entirely.
+        self.allow_attr_cache = False
+
+    def size(self):
+        self._update()
+        return super(FuncToJSONFile, self).size()
+
+    def readfrom(self, *args, **kwargs):
+        self._update()
+        return super(FuncToJSONFile, self).readfrom(*args, **kwargs)
+
+    def _update(self):
+        if not self.stale():
+            return
+        self._mtime = time.time()
+        obj = self.func()
+        self.contents = json.dumps(obj, indent=4, sort_keys=True) + "\n"
+        self.fresh()