Fix Patch Provider pulling in parallel

varats-core/varats/provider/patch/patch_provider.py

@@ -18,6 +18,7 @@
 
 from varats.project.project_util import get_local_project_git_path
 from varats.provider.provider import Provider, ProviderType
+from varats.utils.filesystem_util import lock_file
 from varats.utils.git_commands import pull_current_branch, fetch_repository
 from varats.utils.git_util import (
     CommitHash,
@@ -237,12 +238,10 @@ class PatchProvider(Provider):
     def __init__(self, project: tp.Type[Project]):
         super().__init__(project)
 
-        # BB only performs a fetch so our repo might be out of date
-        pull_current_branch(self._get_patches_repository_path())
+        self._update_local_patches_repo()
+        repo_path = self._get_patches_repository_path()
 
-        patches_project_dir = Path(
-            self._get_patches_repository_path() / self.project.NAME
-        )
+        patches_project_dir = repo_path / self.project.NAME
 
         if not patches_project_dir.is_dir():
             warnings.warn(
@@ -316,6 +315,12 @@ def create_default_provider(
 
     @classmethod
     def _get_patches_repository_path(cls) -> Path:
-        cls.patches_source.fetch()
-
         return Path(target_prefix()) / cls.patches_source.local
+
+    @classmethod
+    def _update_local_patches_repo(cls):
+        lock_path = Path(target_prefix()) / "patch_provider.lock"
+
+        with lock_file(lock_path):
+            cls.patches_source.fetch()
+            pull_current_branch(cls._get_patches_repository_path())

varats-core/varats/utils/filesystem_util.py

@@ -1,6 +1,8 @@
 """Utility functions for handling filesystem related tasks."""
-
+import fcntl
+import os.path
 import typing as tp
+from contextlib import contextmanager
 from pathlib import Path
 
 
@@ -13,3 +15,15 @@ def __init__(self, folder: tp.Union[Path, str]) -> None:
             f"Folder: '{str(folder)}' should be created "
             "but was already present."
         )
+
+
+@contextmanager
+def lock_file(lock_path: Path, lock_mode: int = fcntl.LOCK_EX) -> tp.Generator:
+    open_mode = os.O_RDWR | os.O_CREAT | os.O_TRUNC
+    lock_fd = os.open(lock_path, open_mode)
+    try:
+        fcntl.flock(lock_fd, lock_mode)
+        yield
+    finally:
+        fcntl.flock(lock_fd, fcntl.LOCK_UN)
+        os.close(lock_fd)