Add multi-region support via MODAL_REGION env var

Pass region to modal.Sandbox.create() when set. Supports
us-east-1, us-west-2, eu-west-1, ap-southeast-1.

Author: manascb1344

app.py

@@ -107,6 +107,8 @@ def format(self, record: logging.LogRecord) -> str:
 
 CACHE_VOLUME_NAME = os.environ.get("CACHE_VOLUME_NAME", "") or None
 
+MODAL_REGION = os.environ.get("MODAL_REGION", "") or None
+
 
 def _get_gpu_config(gpu_key: str):
     attr_name = GPU_LABEL_TO_ATTR.get(gpu_key)
@@ -676,10 +678,7 @@ async def github_webhook(request: Request):
             " && exec ./run.sh --jitconfig $GHA_JIT_CONFIG"
         )
 
-        sandbox = modal.Sandbox.create(
-            "bash",
-            "-c",
-            cmd,
+        sandbox_kwargs = dict(
             image=runner_image,
             app=app,
             timeout=TIMEOUT_SECONDS,
@@ -690,6 +689,15 @@ async def github_webhook(request: Request):
             volumes=sandbox_volumes,
             experimental_options={"enable_docker": True},
         )
+        if MODAL_REGION:
+            sandbox_kwargs["region"] = MODAL_REGION
+
+        sandbox = modal.Sandbox.create(
+            "bash",
+            "-c",
+            cmd,
+            **sandbox_kwargs,
+        )
 
         sandbox.set_tags({"job_id": str(job_id)})