[FLOC-3847] Prototype a dataset agent for remote filesystems like NFS

flocker/node/agents/blockdevice.py

@@ -1445,6 +1445,7 @@ class BlockDeviceCalculator(PClass):
     transitions = field(TransitionTable, mandatory=True,
                         factory=TransitionTable.create,
                         initial=DATASET_TRANSITIONS)
+    dataset_states = field(initial=DatasetStates)
 
     def _calculate_dataset_change(self, discovered_dataset, desired_dataset):
         """
@@ -1460,12 +1461,12 @@ def _calculate_dataset_change(self, discovered_dataset, desired_dataset):
         # we detach it.
         desired_state = (desired_dataset.state
                          if desired_dataset is not None
-                         else DatasetStates.NON_MANIFEST)
+                         else self.dataset_states.NON_MANIFEST)
         # If we haven't discovered a dataset, then it is doesn't
         # exist.
         discovered_state = (discovered_dataset.state
                             if discovered_dataset is not None
-                            else DatasetStates.NON_EXISTENT)
+                            else self.dataset_states.NON_EXISTENT)
         if desired_state != discovered_state:
             transition = self.transitions[desired_state][discovered_state]
             return transition.from_state_and_config(

flocker/node/agents/localfs.py

@@ -0,0 +1,61 @@
+"""
+Localhost implementation of ``IRemoteFilesystemAPI``, for testing.
+"""
+
+from uuid import UUID
+from subprocess import check_call
+
+from zope.interface import implementer
+
+from twisted.python.filepath import FilePath
+
+from .remotefs import IRemoteFilesystemAPI, RemoteFilesystem
+
+
+@implementer(IRemoteFilesystemAPI)
+class LocalFilesystem(object):
+    """
+    Local filesystem pretending to be remote filesystem.
+
+    Can't be used for movement across nodes, but otherwise useful for testing.
+    """
+    def __init__(self, root):
+        if not root.exists():
+            root.makedirs()
+        self.root = root()
+
+    def list(self):
+        return [self._to_fs(UUID(child))
+                for child in self.root.listdir()]
+
+    def _child(self, dataset_id):
+        return self.root.child(unicode(dataset_id))
+
+    def _to_fs(self, dataset_id):
+        storage_path = self._child(dataset_id)
+        local_mount_point = None
+        for line in FilePath(
+                b"/proc/self/mountinfo").getContent().splitlines():
+            # let's pretend there's no spaces in paths...
+            parts = line.split()
+            origin = parts[3]
+            destination = parts[4]
+            if origin == storage_path.path:
+                local_mount_point = FilePath(destination)
+                break
+        return RemoteFilesystem(dataset_id=dataset_id,
+                                local_mount_point=local_mount_point)
+
+    def create(self, dataset_id, metadata):
+        self._child(dataset_id).mkdir()
+        return self._to_fs(dataset_id)
+
+    def destroy(self, dataset_id):
+        self._child(dataset_id).remove()
+
+    def mount(self, dataset_id, path):
+        check_call([b"mount", b"--bind", self._child(dataset_id).path,
+                    path.path])
+
+    def umount(self, dataset_id, path):
+        check_call([b"umount", path.path])