Adding Override Option for TorchX Role (#956)

Summary:
Pull Request resolved: #956

Adds a generic way to override the internal values of the Role. Allows async overriding of role values and enable Async Packaging

Reviewed By: Sanjay-Ganeshan

Differential Revision: D62591176

torchx/specs/api.py

@@ -7,7 +7,9 @@
 
 # pyre-strict
 
+import asyncio
 import copy
+import inspect
 import json
 import re
 import typing
@@ -370,6 +372,24 @@ class Role:
     mounts: List[Union[BindMount, VolumeMount, DeviceMount]] = field(
         default_factory=list
     )
+    overrides: Dict[str, Any] = field(default_factory=dict)
+
+    # pyre-ignore
+    def __getattribute__(self, attrname: str) -> Any:
+        if attrname == "overrides":
+            return super().__getattribute__(attrname)
+        try:
+            ov = super().__getattribute__("overrides")
+        except AttributeError:
+            ov = {}
+        if attrname in ov:
+            if inspect.isawaitable(ov[attrname]):
+                result = asyncio.get_event_loop().run_until_complete(ov[attrname])
+            else:
+                result = ov[attrname]()
+            setattr(self, attrname, result)
+            del ov[attrname]
+        return super().__getattribute__(attrname)
 
     def pre_proc(
         self,

torchx/specs/test/api_test.py

@@ -7,6 +7,7 @@
 
 # pyre-strict
 
+import asyncio
 import os
 import time
 import unittest
@@ -276,6 +277,28 @@ def test_retry_policies(self) -> None:
             },
         )
 
+    def test_override_role(self) -> None:
+        default = Role(
+            "foobar",
+            "torch",
+            overrides={"image": lambda: "base", "entrypoint": lambda: "nentry"},
+        )
+        self.assertEqual("base", default.image)
+        self.assertEqual("nentry", default.entrypoint)
+
+    def test_async_override_role(self) -> None:
+        async def update(value: str, time_seconds: int) -> str:
+            await asyncio.sleep(time_seconds)
+            return value
+
+        default = Role(
+            "foobar",
+            "torch",
+            overrides={"image": update("base", 1), "entrypoint": update("nentry", 2)},
+        )
+        self.assertEqual("base", default.image)
+        self.assertEqual("nentry", default.entrypoint)
+
 
 class AppHandleTest(unittest.TestCase):
     def test_parse_malformed_app_handles(self) -> None: