particle-os/debian-forge
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

objectstore: copy on write semantics for Object

Browse source 
Since Object knows its base now, the initialization of the tree
with the content of its base can be delayed until the moment
someone wants to actually modify the tree, thus implementing
copy on write semantics. For this a new `write` method is added
that will initialize the base and return the writable tree. It
should be used instead of `path` whenever the a client wants to
write to the tree of the Object.
Adapt the pipeline and the tests to use the new `write` method
in all the appropriate places.
NB: since the intention can not be inferred when using `path`
directly, the Object is still being initialized there.
This commit is contained in:
Christian Kellner 2020-02-18 09:50:55 +01:00 • committed by Tom Gundersen
parent 0874b80734
commit 39213b7f44
3 changed files with 27 additions and 11 deletions
Download patch file Download diff file Expand all files Collapse all files

14
osbuild/objectstore.py
View file

@ -73,12 +73,22 @@ class Object:
@contextlib.contextmanager
def open(self):
"""Open the directory and return the file descriptor"""
if self._base_path and not self._init:
path = self._base_path
else:
path = self._tree
try:
fd = os.open(self.path, os.O_DIRECTORY)
fd = os.open(path, os.O_DIRECTORY)
yield fd
finally:
os.close(fd)
def write(self) -> str:
"""Return a path that can be written to"""
self.init()
return self._tree
def store_tree(self, destination: str):
"""Store the tree at destination and reset itself
@ -167,8 +177,8 @@ class ObjectStore:
if base_id:
# if we were given a base id, resolve its path and set it
# as the base_path of the object
# NB: `obj` does not get initialized explicitly here
obj.base_path = self.resolve_ref(base_id)
obj.init()
yield obj

4
osbuild/pipeline.py
View file

@ -272,7 +272,7 @@ class Pipeline:
try:
with object_store.new(self.tree_id, base_id=base) as tree:
for stage in self.stages[base_idx + 1:]:
r = stage.run(tree.path,
r = stage.run(tree.write(),
self.runner,
build_tree,
store,
@ -298,7 +298,7 @@ class Pipeline:
r = self.assembler.run(tree,
self.runner,
build_tree,
output_dir=output_dir.path,
output_dir=output_dir.write(),
interactive=interactive,
libdir=libdir,
var=store)

20
test/test_objectstore.py
View file

@ -25,7 +25,8 @@ class TestObjectStore(unittest.TestCase):
with tempfile.TemporaryDirectory(dir="/var/tmp") as tmp:
object_store = objectstore.ObjectStore(tmp)
with object_store.new("a") as tree:
p = Path(f"{tree.path}/A")
path = tree.write()
p = Path(f"{path}/A")
p.touch()
assert os.path.exists(f"{object_store.refs}/a")
@ -35,9 +36,10 @@ class TestObjectStore(unittest.TestCase):
assert len(os.listdir(f"{object_store.refs}/a/")) == 1
with object_store.new("b") as tree:
p = Path(f"{tree.path}/A")
path = tree.write()
p = Path(f"{path}/A")
p.touch()
p = Path(f"{tree.path}/B")
p = Path(f"{path}/B")
p.touch()
assert os.path.exists(f"{object_store.refs}/b")
@ -51,12 +53,14 @@ class TestObjectStore(unittest.TestCase):
with tempfile.TemporaryDirectory(dir="/var/tmp") as tmp:
object_store = objectstore.ObjectStore(tmp)
with object_store.new("a") as tree:
p = Path(f"{tree.path}/A")
path = tree.write()
p = Path(f"{path}/A")
p.touch()
with object_store.new("b") as tree:
path = tree.write()
shutil.copy2(f"{object_store.refs}/a/A",
f"{tree.path}/A")
f"{path}/A")
assert os.path.exists(f"{object_store.refs}/a")
assert os.path.exists(f"{object_store.refs}/a/A")
@ -70,10 +74,12 @@ class TestObjectStore(unittest.TestCase):
def test_snapshot(self):
object_store = objectstore.ObjectStore(self.store)
with object_store.new("b") as tree:
p = Path(f"{tree.path}/A")
path = tree.write()
p = Path(f"{path}/A")
p.touch()
object_store.snapshot(tree, "a")
p = Path(f"{tree.path}/B")
path = tree.write()
p = Path(f"{path}/B")
p.touch()
# check the references exist