minor ext fixes (#16684)

## Summary & Motivation

Grab bag of non-user-facing fixes for consistency in variable names etc.

## How I Tested These Changes

Existing test suite.

python_modules/dagster-ext/MANIFEST.in

@@ -1,3 +1,3 @@
 include README.md
 include LICENSE
-include dagster_external/py.typed
+include dagster_ext/py.typed

python_modules/dagster-ext/dagster_ext/__init__.py

@@ -66,7 +66,7 @@ class ExtMessage(TypedDict):
     params: Optional[Mapping[str, Any]]
 
 
-# ##### EXTERNAL EXECUTION CONTEXT
+# ##### EXT CONTEXT
 
 
 class ExtContextData(TypedDict):
@@ -624,11 +624,11 @@ def __init__(
         message_channel: ExtMessageWriterChannel,
     ) -> None:
         self._data = data
-        self.message_channel = message_channel
+        self._message_channel = message_channel
 
     def _write_message(self, method: str, params: Optional[Mapping[str, Any]] = None) -> None:
         message = ExtMessage(method=method, params=params)
-        self.message_channel.write_message(message)
+        self._message_channel.write_message(message)
 
     # ########################
     # ##### PUBLIC API

python_modules/dagster/dagster/_core/ext/utils.py

@@ -35,9 +35,6 @@
 _CONTEXT_INJECTOR_FILENAME = "context"
 _MESSAGE_READER_FILENAME = "messages"
 
-_CONTEXT_INJECTOR_FILENAME = "context"
-_MESSAGE_READER_FILENAME = "messages"
-
 
 class ExtFileContextInjector(ExtContextInjector):
     def __init__(self, path: str):
@@ -112,7 +109,7 @@ def read_messages(
     ) -> Iterator[ExtParams]:
         with tempfile.TemporaryDirectory() as tempdir:
             with ExtFileMessageReader(
-                os.path.join(tempdir, _CONTEXT_INJECTOR_FILENAME)
+                os.path.join(tempdir, _MESSAGE_READER_FILENAME)
             ).read_messages(handler) as params:
                 yield params
 
@@ -199,15 +196,15 @@ def ext_protocol(
     that need to be provided to the external process.
     """
     context_data = build_external_execution_context_data(context, extras)
-    msg_handler = ExtMessageHandler(context)
+    message_handler = ExtMessageHandler(context)
     with context_injector.inject_context(
         context_data,
     ) as ci_params, message_reader.read_messages(
-        msg_handler,
+        message_handler,
     ) as mr_params:
         yield ExtOrchestrationContext(
             context_data=context_data,
-            message_handler=msg_handler,
+            message_handler=message_handler,
             context_injector_params=ci_params,
             message_reader_params=mr_params,
         )

python_modules/libraries/dagster-aws/dagster_aws/ext.py

@@ -13,7 +13,7 @@
 
 
 class ExtS3MessageReader(ExtBlobStoreMessageReader):
-    def __init__(self, *, interval: int = 10, bucket: str, client: boto3.client):
+    def __init__(self, *, interval: float = 10, bucket: str, client: boto3.client):
         super().__init__(interval=interval)
         self.bucket = check.str_param(bucket, "bucket")
         self.key_prefix = "".join(random.choices(string.ascii_letters, k=30))

python_modules/libraries/dagster-k8s/dagster_k8s/ext.py

@@ -158,15 +158,15 @@ def run(
             extras=extras,
             context_injector=self.context_injector,
             message_reader=self.message_reader,
-        ) as ext_process:
+        ) as ext_context:
             namespace = namespace or "default"
             pod_name = get_pod_name(context.run_id, context.op.name)
             pod_body = build_pod_body(
                 pod_name=pod_name,
                 image=image,
                 command=command,
                 env_vars={
-                    **ext_process.get_external_process_env_vars(),
+                    **ext_context.get_external_process_env_vars(),
                     **(self.env or {}),
                     **(env or {}),
                 },