Tidy up changes added with PR#115 and limit it to only work with Python3.12 in Lambda. (#124)

* Tidy up changes added with PR#115 andlimit it to only work with Python3.12 in Lambda.
---------

Co-authored-by: Pushkar Chawda <chawdapu@amazon.com>

Author: pushkarchawda

awslambdaric/bootstrap.py

@@ -462,8 +462,14 @@ def run(app_root, handler, lambda_runtime_api_addr):
     sys.stdout = Unbuffered(sys.stdout)
     sys.stderr = Unbuffered(sys.stderr)
 
+    use_thread_for_polling_next = (
+        os.environ.get("AWS_EXECUTION_ENV") == "AWS_Lambda_python3.12"
+    )
+
     with create_log_sink() as log_sink:
-        lambda_runtime_client = LambdaRuntimeClient(lambda_runtime_api_addr)
+        lambda_runtime_client = LambdaRuntimeClient(
+            lambda_runtime_api_addr, use_thread_for_polling_next
+        )
 
         try:
             _setup_logging(_AWS_LAMBDA_LOG_FORMAT, _AWS_LAMBDA_LOG_LEVEL, log_sink)

awslambdaric/lambda_runtime_client.py

@@ -3,8 +3,8 @@
 """
 
 import sys
-from concurrent.futures import ThreadPoolExecutor
 from awslambdaric import __version__
+from .lambda_runtime_exception import FaultException
 
 
 def _user_agent():
@@ -49,8 +49,9 @@ class LambdaRuntimeClient(object):
     and response. It allows for function authors to override the the default implementation, LambdaMarshaller which
     unmarshals and marshals JSON, to an instance of a class that implements the same interface."""
 
-    def __init__(self, lambda_runtime_address):
+    def __init__(self, lambda_runtime_address, use_thread_for_polling_next=False):
         self.lambda_runtime_address = lambda_runtime_address
+        self.use_thread_for_polling_next = use_thread_for_polling_next
 
     def post_init_error(self, error_response_data):
         # These imports are heavy-weight. They implicitly trigger `import ssl, hashlib`.
@@ -69,9 +70,23 @@ def post_init_error(self, error_response_data):
             raise LambdaRuntimeClientError(endpoint, response.code, response_body)
 
     def wait_next_invocation(self):
-        with ThreadPoolExecutor() as e:
-            fut = e.submit(runtime_client.next)
-        response_body, headers = fut.result()
+        # Calling runtime_client.next() from a separate thread unblocks the main thread,
+        # which can then process signals.
+        if self.use_thread_for_polling_next:
+            try:
+                from concurrent.futures import ThreadPoolExecutor
+
+                with ThreadPoolExecutor(max_workers=1) as executor:
+                    future = executor.submit(runtime_client.next)
+                response_body, headers = future.result()
+            except Exception as e:
+                raise FaultException(
+                    FaultException.LAMBDA_RUNTIME_CLIENT_ERROR,
+                    "LAMBDA_RUNTIME Failed to get next invocation: {}".format(str(e)),
+                    None,
+                )
+        else:
+            response_body, headers = runtime_client.next()
         return InvocationRequest(
             invoke_id=headers.get("Lambda-Runtime-Aws-Request-Id"),
             x_amzn_trace_id=headers.get("Lambda-Runtime-Trace-Id"),

awslambdaric/lambda_runtime_exception.py

@@ -12,6 +12,7 @@ class FaultException(Exception):
     BUILT_IN_MODULE_CONFLICT = "Runtime.BuiltInModuleConflict"
     MALFORMED_HANDLER_NAME = "Runtime.MalformedHandlerName"
     LAMBDA_CONTEXT_UNMARSHAL_ERROR = "Runtime.LambdaContextUnmarshalError"
+    LAMBDA_RUNTIME_CLIENT_ERROR = "Runtime.LambdaRuntimeClientError"
 
     def __init__(self, exception_type, msg, trace=None):
         self.msg = msg

tests/test_lambda_runtime_client.py

@@ -84,6 +84,21 @@ def test_wait_next_invocation(self, mock_runtime_client):
         self.assertEqual(event_request.content_type, "application/json")
         self.assertEqual(event_request.event_body, response_body)
 
+        # Using ThreadPoolExecutor to polling next()
+        runtime_client = LambdaRuntimeClient("localhost:1234", True)
+
+        event_request = runtime_client.wait_next_invocation()
+
+        self.assertIsNotNone(event_request)
+        self.assertEqual(event_request.invoke_id, "RID1234")
+        self.assertEqual(event_request.x_amzn_trace_id, "TID1234")
+        self.assertEqual(event_request.invoked_function_arn, "FARN1234")
+        self.assertEqual(event_request.deadline_time_in_ms, 12)
+        self.assertEqual(event_request.client_context, "client_context")
+        self.assertEqual(event_request.cognito_identity, "cognito_identity")
+        self.assertEqual(event_request.content_type, "application/json")
+        self.assertEqual(event_request.event_body, response_body)
+
     @patch("http.client.HTTPConnection", autospec=http.client.HTTPConnection)
     def test_post_init_error(self, MockHTTPConnection):
         mock_conn = MockHTTPConnection.return_value