locks/storage plugins: access via Manager, eliminate global vars

Author: Adam Höse

Author: grahamc

nixops/locks/__init__.py

@@ -38,6 +38,3 @@ def lock(self, **kwargs) -> None:
     # the type definition allows adding new arguments later.
     def unlock(self, **kwargs) -> None:
         raise NotImplementedError
-
-
-lock_drivers: Dict[str, Type[LockDriver]] = {}

nixops/plugin.py

@@ -1,4 +1,4 @@
-from nixops.storage import BackendRegistration
+from nixops.storage import StorageBackend
 
 from nixops.storage.legacy import LegacyBackend
 from nixops.storage.memory import MemoryBackend
@@ -9,7 +9,7 @@
 
 
 class InternalPlugin(nixops.plugins.Plugin):
-    def storage_backends(self) -> BackendRegistration:
+    def storage_backends(self) -> Dict[str, Type[StorageBackend]]:
         return {"legacy": LegacyBackend, "memory": MemoryBackend}
 
     def lock_drivers(self) -> Dict[str, Type[LockDriver]]:

nixops/plugins/__init__.py

@@ -3,7 +3,7 @@
 from nixops.backends import MachineState
 from typing import List, Dict, Optional, Union, Tuple, Type
 
-from nixops.storage import BackendRegistration
+from nixops.storage import StorageBackend
 from nixops.locks import LockDriver
 from functools import lru_cache
 from typing import Generator
@@ -99,7 +99,7 @@ def docs(self) -> List[Tuple[str, str]]:
     def lock_drivers(self) -> Dict[str, Type[LockDriver]]:
         return {}
 
-    def storage_backends(self) -> BackendRegistration:
+    def storage_backends(self) -> Dict[str, Type[StorageBackend]]:
         """ Extend the core nixops cli parser
         :return a set of plugin parser extensions
         """

nixops/plugins/manager.py

@@ -4,11 +4,12 @@
 from typing import List, Dict, Generator, Tuple, Any, Set
 import importlib
 
-from nixops.storage import storage_backends
-from nixops.locks import lock_drivers
+from nixops.storage import StorageBackend
+from nixops.locks import LockDriver
 from . import get_plugins, MachineHooks, DeploymentHooks
 import nixops.ansi
 import nixops
+from typing import Type
 import sys
 
 
@@ -83,7 +84,9 @@ def docs() -> Generator[Tuple[str, str], None, None]:
             yield from plugin.docs()
 
     @staticmethod
-    def storage_backends():
+    def storage_backends() -> Dict[str, Type[StorageBackend]]:
+        storage_backends: Dict[str, Type[StorageBackend]] = {}
+
         for plugin in get_plugins():
             for name, backend in plugin.storage_backends().items():
                 if name not in storage_backends:
@@ -95,8 +98,12 @@ def storage_backends():
                         )
                     )
 
+        return storage_backends
+
     @staticmethod
-    def lock_drivers():
+    def lock_drivers() -> Dict[str, Type[LockDriver]]:
+        lock_drivers: Dict[str, Type[LockDriver]] = {}
+
         for plugin in get_plugins():
             for name, driver in plugin.lock_drivers().items():
                 if name not in lock_drivers:
@@ -107,3 +114,5 @@ def lock_drivers():
                             f"Two plugins tried to provide the '{name}' lock driver."
                         )
                     )
+
+        return lock_drivers

nixops/script_defs.py

@@ -30,8 +30,6 @@
 
 from nixops.plugins import get_plugin_manager
 from nixops.evaluation import eval_network
-from nixops.storage import storage_backends
-from nixops.locks import lock_drivers
 
 
 PluginManager.load()
@@ -49,6 +47,7 @@ def deployment(args: Namespace) -> Generator[nixops.deployment.Deployment, None,
 def network_state(args: Namespace) -> Generator[nixops.statefile.StateFile, None, None]:
     network_file: str = args.network_file
     network = eval_network(network_file)
+    storage_backends = PluginManager.storage_backends()
     storage_class: Optional[Type[StorageBackend]] = storage_backends.get(
         network.storage.provider
     )
@@ -63,6 +62,7 @@ def network_state(args: Namespace) -> Generator[nixops.statefile.StateFile, None
 
     lock: LockDriver
     lock_class: Type[LockDriver]
+    lock_drivers = PluginManager.lock_drivers()
     try:
         lock_class = lock_drivers[network.lock.provider]
     except KeyError:

nixops/storage/__init__.py

@@ -51,9 +51,3 @@ def onOpen(self, sf: nixops.statefile.StateFile, **kwargs) -> None:
     # the type definition allows adding new arguments later.
     def uploadFromFile(self, path: str, **kwargs) -> None:
         raise NotImplementedError
-
-
-BackendRegistration = Dict[str, Type[StorageBackend]]
-
-
-storage_backends: Dict[str, Type[StorageBackend]] = {}