Support specifying a list of regions to run on

- Rename the '_experimental_scheduler_placement' proto field to just
  'scheduler_placement'.
- Disallow specifying both 'region=' and
  '_experimental_scheduler_placement='.
- Make things backwards compatible, with
  '_experimental_scheduler_placement=...' and
  'SchedulerPlacement(region=...)', both at the API level and at the proto
  level. For the latter, the field is marked as deprecated and will be
  normalized away on the server.
- Support specifying regions for 'modal shell'.

modal/app.py

@@ -508,6 +508,7 @@ def function(
             bool
         ] = None,  # Set this to True if it's a non-generator function returning a [sync/async] generator object
         cloud: Optional[str] = None,  # Cloud provider to run the function on. Possible values are aws, gcp, oci, auto.
+        region: Optional[Union[str, Sequence[str]]] = None,  # Region or regions to run the function on.
         enable_memory_snapshot: bool = False,  # Enable memory checkpointing for faster cold starts.
         checkpointing_enabled: Optional[bool] = None,  # Deprecated
         block_network: bool = False,  # Whether to block network access
@@ -579,6 +580,12 @@ def wrapped(
             if is_generator is None:
                 is_generator = inspect.isgeneratorfunction(raw_f) or inspect.isasyncgenfunction(raw_f)
 
+            scheduler_placement: Optional[SchedulerPlacement] = _experimental_scheduler_placement
+            if region:
+                if scheduler_placement:
+                    raise InvalidError("`region` and `_experimental_scheduler_placement` cannot be used together")
+                scheduler_placement = SchedulerPlacement(region=region)
+
             function = _Function.from_args(
                 info,
                 app=self,
@@ -608,9 +615,9 @@ def wrapped(
                 allow_background_volume_commits=_allow_background_volume_commits,
                 block_network=block_network,
                 max_inputs=max_inputs,
+                scheduler_placement=scheduler_placement,
                 _experimental_boost=_experimental_boost,
                 _experimental_scheduler=_experimental_scheduler,
-                _experimental_scheduler_placement=_experimental_scheduler_placement,
             )
 
             self._add_function(function)
@@ -646,6 +653,7 @@ def cls(
         timeout: Optional[int] = None,  # Maximum execution time of the function in seconds.
         keep_warm: Optional[int] = None,  # An optional number of containers to always keep warm.
         cloud: Optional[str] = None,  # Cloud provider to run the function on. Possible values are aws, gcp, oci, auto.
+        region: Optional[Union[str, Sequence[str]]] = None,  # Region or regions to run the function on.
         enable_memory_snapshot: bool = False,  # Enable memory checkpointing for faster cold starts.
         checkpointing_enabled: Optional[bool] = None,  # Deprecated
         block_network: bool = False,  # Whether to block network access
@@ -687,6 +695,7 @@ def cls(
             interactive=interactive,
             keep_warm=keep_warm,
             cloud=cloud,
+            region=region,
             enable_memory_snapshot=enable_memory_snapshot,
             checkpointing_enabled=checkpointing_enabled,
             block_network=block_network,
@@ -730,6 +739,7 @@ async def spawn_sandbox(
         workdir: Optional[str] = None,  # Working directory of the sandbox.
         gpu: GPU_T = None,
         cloud: Optional[str] = None,
+        region: Optional[Union[str, Sequence[str]]] = None,  # Region or regions to run the sandbox on.
         cpu: Optional[float] = None,  # How many CPU cores to request. This is a soft limit.
         memory: Optional[
             Union[int, Tuple[int, int]]
@@ -769,6 +779,7 @@ async def spawn_sandbox(
             workdir=workdir,
             gpu=gpu,
             cloud=cloud,
+            region=region,
             cpu=cpu,
             memory=memory,
             network_file_systems=network_file_systems,

modal/cli/run.py

@@ -344,7 +344,11 @@ def shell(
     ),
     cloud: Optional[str] = typer.Option(
         default=None,
-        help="Cloud provider to run the function on. Possible values are `aws`, `gcp`, `oci`, `auto` (if not using FUNC_REF).",
+        help="Cloud provider to run the shell on. Possible values are `aws`, `gcp`, `oci`, `auto` (if not using FUNC_REF).",
+    ),
+    region: Optional[str] = typer.Option(
+        default=None,
+        help="Region(s) to run the shell on. Can be a single region or a comma-separated list to choose from (if not using FUNC_REF).",
     ),
 ):
     """Run an interactive shell inside a Modal image.
@@ -392,10 +396,19 @@ def shell(
             cpu=function_spec.cpu,
             memory=function_spec.memory,
             volumes=function_spec.volumes,
+            scheduler_placement=function_spec.scheduler_placement,
             _allow_background_volume_commits=True,
         )
     else:
         modal_image = Image.from_registry(image, add_python=add_python) if image else None
-        start_shell = partial(interactive_shell, image=modal_image, cpu=cpu, memory=memory, gpu=gpu, cloud=cloud)
+        start_shell = partial(
+            interactive_shell,
+            image=modal_image,
+            cpu=cpu,
+            memory=memory,
+            gpu=gpu,
+            cloud=cloud,
+            region=region.split(",") if region else [],
+        )
 
     start_shell(app, cmd=[cmd], environment_name=env, timeout=3600)

modal/functions.py

@@ -250,6 +250,7 @@ class _FunctionSpec:
     cloud: Optional[str]
     cpu: Optional[float]
     memory: Optional[Union[int, Tuple[int, int]]]
+    scheduler_placement: Optional[SchedulerPlacement]
 
 
 class _Function(_Object, type_prefix="fu"):
@@ -303,7 +304,7 @@ def from_args(
         cloud: Optional[str] = None,
         _experimental_boost: bool = False,
         _experimental_scheduler: bool = False,
-        _experimental_scheduler_placement: Optional[SchedulerPlacement] = None,
+        scheduler_placement: Optional[SchedulerPlacement] = None,
         is_builder_function: bool = False,
         is_auto_snapshot: bool = False,
         enable_memory_snapshot: bool = False,
@@ -374,6 +375,7 @@ def from_args(
             cloud=cloud,
             cpu=cpu,
             memory=memory,
+            scheduler_placement=scheduler_placement,
         )
 
         if info.cls and not is_auto_snapshot:
@@ -397,7 +399,7 @@ def from_args(
                     cpu=cpu,
                     is_builder_function=True,
                     is_auto_snapshot=True,
-                    _experimental_scheduler_placement=_experimental_scheduler_placement,
+                    scheduler_placement=scheduler_placement,
                 )
                 image = _Image._from_args(
                     base_images={"base": image},
@@ -596,9 +598,7 @@ async def _load(self: _Function, resolver: Resolver, existing_object_id: Optiona
                 cloud_bucket_mounts=cloud_bucket_mounts_to_proto(cloud_bucket_mounts),
                 _experimental_boost=_experimental_boost,
                 _experimental_scheduler=_experimental_scheduler,
-                _experimental_scheduler_placement=_experimental_scheduler_placement.proto
-                if _experimental_scheduler_placement
-                else None,
+                scheduler_placement=scheduler_placement.proto if scheduler_placement else None,
             )
             request = api_pb2.FunctionCreateRequest(
                 app_id=resolver.app_id,

modal/sandbox.py

@@ -242,6 +242,7 @@ def _new(
         workdir: Optional[str] = None,
         gpu: GPU_T = None,
         cloud: Optional[str] = None,
+        region: Optional[Union[str, Sequence[str]]] = None,
         cpu: Optional[float] = None,
         memory: Optional[Union[int, Tuple[int, int]]] = None,
         network_file_systems: Dict[Union[str, os.PathLike], _NetworkFileSystem] = {},
@@ -261,6 +262,12 @@ def _new(
             raise InvalidError("network_file_systems must be a dict[str, NetworkFileSystem] where the keys are paths")
         validated_network_file_systems = validate_mount_points("Network file system", network_file_systems)
 
+        scheduler_placement: Optional[SchedulerPlacement] = _experimental_scheduler_placement
+        if region:
+            if scheduler_placement:
+                raise InvalidError("`region` and `_experimental_scheduler_placement` cannot be used together")
+            scheduler_placement = SchedulerPlacement(region=region)
+
         # Validate volumes
         validated_volumes = validate_volumes(volumes)
         cloud_bucket_mounts = [(k, v) for k, v in validated_volumes if isinstance(v, _CloudBucketMount)]
@@ -304,9 +311,7 @@ async def _load(self: _Sandbox, resolver: Resolver, _existing_object_id: Optiona
                 volume_mounts=volume_mounts,
                 pty_info=pty_info,
                 _experimental_scheduler=_experimental_scheduler,
-                _experimental_scheduler_placement=_experimental_scheduler_placement.proto
-                if _experimental_scheduler_placement
-                else None,
+                scheduler_placement=scheduler_placement.proto if scheduler_placement else None,
             )
 
             create_req = api_pb2.SandboxCreateRequest(app_id=resolver.app_id, definition=definition)

modal/scheduler_placement.py

@@ -1,5 +1,5 @@
 # Copyright Modal Labs 2024
-from typing import Optional
+from typing import Optional, Sequence, Union
 
 from modal_proto import api_pb2
 
@@ -11,7 +11,7 @@ class SchedulerPlacement:
 
     def __init__(
         self,
-        region: Optional[str] = None,
+        region: Optional[Union[str, Sequence[str]]] = None,
         zone: Optional[str] = None,
         spot: Optional[bool] = None,
     ):
@@ -20,8 +20,14 @@ def __init__(
         if spot is not None:
             _lifecycle = "spot" if spot else "on-demand"
 
+        regions = []
+        if region:
+            if isinstance(region, str):
+                regions = [region]
+            else:
+                regions = list(region)
         self.proto = api_pb2.SchedulerPlacement(
-            _region=region,
+            regions=regions,
             _zone=zone,
             _lifecycle=_lifecycle,
         )

modal_proto/api.proto

@@ -915,15 +915,17 @@ message Function {
   // If set, tasks will be scheduled using the new scheduler, which also knows
   // to look at fine-grained placement constraints.
   bool _experimental_scheduler = 49;
-  optional SchedulerPlacement _experimental_scheduler_placement = 50;
+  optional SchedulerPlacement scheduler_placement = 50;
 }
 
 message SchedulerPlacement {
   // TODO(irfansharif):
   // - Fold in cloud, resource needs here too.
-  // - Allow specifying list of regions, zones, cloud, fallback and alternative
+  // - Allow specifying list of zones, cloud, fallback and alternative
   //   GPU types.
-  optional string _region = 1;
+  optional string _region = 1 [deprecated=true];
+
+  repeated string regions = 4;
   optional string _zone = 2;
   optional string _lifecycle = 3; // "on-demand" or "spot", else ignored
 }
@@ -1007,7 +1009,7 @@ message FunctionGetResponse {
   FunctionHandleMetadata handle_metadata = 2;
 }
 
- 
+
 message FunctionUpdateSchedulingParamsRequest {
   string function_id = 1;
   uint32 warm_pool_size_override = 2;
@@ -1572,7 +1574,7 @@ message Sandbox {
   // If set, tasks will be scheduled using the new scheduler, which also knows
   // to look at fine-grained placement constraints.
   bool _experimental_scheduler = 16;
-  optional SchedulerPlacement _experimental_scheduler_placement = 17;
+  optional SchedulerPlacement scheduler_placement = 17;
 }
 
 message SandboxCreateRequest {

test/scheduler_placement_test.py

@@ -15,21 +15,45 @@
         spot=False,
     ),
 )
-def f():
+def f1():
+    pass
+
+
+@app.function(
+    region="us-east-1",
+)
+def f2():
+    pass
+
+
+@app.function(
+    region=["us-east-1", "us-west-2"],
+)
+def f3():
     pass
 
 
 def test_fn_scheduler_placement(servicer, client):
     with app.run(client=client):
-        assert len(servicer.app_functions) == 1
-        fn = servicer.app_functions["fu-1"]
-        assert fn._experimental_scheduler
-        assert fn._experimental_scheduler_placement == api_pb2.SchedulerPlacement(
-            _region="us-east-1",
+        assert len(servicer.app_functions) == 3
+        fn1 = servicer.app_functions["fu-1"]  # f1
+        assert fn1._experimental_scheduler
+        assert fn1.scheduler_placement == api_pb2.SchedulerPlacement(
+            regions=["us-east-1"],
             _zone="us-east-1a",
             _lifecycle="on-demand",
         )
 
+        fn2 = servicer.app_functions["fu-2"]  # f2
+        assert fn2.scheduler_placement == api_pb2.SchedulerPlacement(
+            regions=["us-east-1"],
+        )
+
+        fn3 = servicer.app_functions["fu-3"]  # f3
+        assert fn3.scheduler_placement == api_pb2.SchedulerPlacement(
+            regions=["us-east-1", "us-west-2"],
+        )
+
 
 @skip_non_linux
 def test_sandbox_scheduler_placement(client, servicer):
@@ -39,19 +63,13 @@ def test_sandbox_scheduler_placement(client, servicer):
             "-c",
             "echo bye >&2 && sleep 1 && echo hi && exit 42",
             timeout=600,
+            region="us-east-1",
             _experimental_scheduler=True,
-            _experimental_scheduler_placement=SchedulerPlacement(
-                region="us-east-1",
-                zone="us-east-1a",
-                spot=False,
-            ),
         )
 
         assert len(servicer.sandbox_defs) == 1
         sb_def = servicer.sandbox_defs[0]
-        assert sb_def._experimental_scheduler
-        assert sb_def._experimental_scheduler_placement == api_pb2.SchedulerPlacement(
-            _region="us-east-1",
-            _zone="us-east-1a",
-            _lifecycle="on-demand",
+        assert sb_def.scheduler_placement == api_pb2.SchedulerPlacement(
+            regions=["us-east-1"],
         )
+        assert sb_def._experimental_scheduler