Files
dvc/tests/unit/test_rwlock.py
T
Ruslan Kuprieiev e384685715 dvc: release locks when running a command
Currently only one instance of dvc could run in a particular repo
because of the `.dvc/lock`. That gets furstrating when you are running
some long-running command and blocked from doing anything else.
This PR solved that issue for `dvc run` by releasing the repo lock
while running the command. To protect against conflicts, we now use
rwlock, which keeps the list of readers and writers for particular
paths. The process looks like this:

1) aquire read locks for deps;
2) aquire write locks for outs;
3) release repo lock;
4) run cmd;
5) aquire repo lock;
6) release write locks for outs;
7) release read locks for outs;

We also take rwlocks for operations such as `import`, `add` and `checkout`
to ensure that we won't hit the same files that are being used by
another `dvc run` in the background.

We don't aquire rwlocks for the stage file itself, as we don't really
care about anyone overwriting a stage file, as there is a very little
difference here between parallel runs and sequential runs that overwrite
the same stage file.

Next steps might be to release repo lock on `import`(when dowloading
stuff) and when computing checksums or copying files.

Fixes #755
2019-12-13 10:38:10 +02:00

99 lines
2.6 KiB
Python

from __future__ import unicode_literals
import os
import pytest
from dvc.rwlock import (
rwlock,
_edit_rwlock,
RWLockFileFormatError,
RWLockFileCorruptedError,
)
from dvc.lock import LockError
from dvc.utils.compat import fspath
from dvc.path_info import PathInfo
def test_rwlock(tmp_path):
path = fspath(tmp_path)
foo = PathInfo("foo")
with rwlock(path, "cmd1", [foo], []):
with pytest.raises(LockError):
with rwlock(path, "cmd2", [], [foo]):
pass
with rwlock(path, "cmd1", [], [foo]):
with pytest.raises(LockError):
with rwlock(path, "cmd2", [foo], []):
pass
with rwlock(path, "cmd1", [], [foo]):
with pytest.raises(LockError):
with rwlock(path, "cmd2", [], [foo]):
pass
def test_rwlock_reentrant(tmp_path):
path = fspath(tmp_path)
foo = PathInfo("foo")
with rwlock(path, "cmd1", [], [foo]):
with rwlock(path, "cmd1", [], [foo]):
pass
with _edit_rwlock(path) as lock:
assert lock == {
"read": {},
"write": {"foo": {"cmd": "cmd1", "pid": os.getpid()}},
}
with rwlock(path, "cmd", [foo], []):
with rwlock(path, "cmd", [foo], []):
pass
with _edit_rwlock(path) as lock:
assert lock == {
"read": {"foo": [{"cmd": "cmd", "pid": os.getpid()}]},
"write": {},
}
def test_rwlock_subdirs(tmp_path):
path = fspath(tmp_path)
foo = PathInfo("foo")
subfoo = PathInfo("foo/subfoo")
with rwlock(path, "cmd1", [foo], []):
with pytest.raises(LockError):
with rwlock(path, "cmd2", [], [subfoo]):
pass
with rwlock(path, "cmd1", [], [subfoo]):
with pytest.raises(LockError):
with rwlock(path, "cmd2", [foo], []):
pass
with rwlock(path, "cmd1", [], [subfoo]):
with pytest.raises(LockError):
with rwlock(path, "cmd2", [], [foo]):
pass
with rwlock(path, "cmd1", [subfoo], []):
with rwlock(path, "cmd2", [foo], []):
pass
def test_broken_rwlock(tmp_path):
dir_path = fspath(tmp_path)
path = tmp_path / "rwlock"
path.write_text('{"broken": "format"}', encoding="utf-8")
with pytest.raises(RWLockFileFormatError):
with _edit_rwlock(dir_path):
pass
path.write_text("{broken json", encoding="utf-8")
with pytest.raises(RWLockFileCorruptedError):
with _edit_rwlock(dir_path):
pass