diff --git a/opensearchpy/connection/http_requests.py b/opensearchpy/connection/http_requests.py
index 9bf83004..5eb7bc70 100644
--- a/opensearchpy/connection/http_requests.py
+++ b/opensearchpy/connection/http_requests.py
@@ -88,6 +88,7 @@ def __init__(
         pool_maxsize: Any = None,
         **kwargs: Any
     ) -> None:
+        self.kwargs=kwargs
         if not REQUESTS_AVAILABLE:
             raise ImproperlyConfigured(
                 "Please install requests to use RequestsHttpConnection."
@@ -166,6 +167,10 @@ def perform_request(  # type: ignore
         ignore: Collection[int] = (),
         headers: Optional[Mapping[str, str]] = None,
     ) -> Any:
+        
+        calculate_service_time=False
+        if "calculate_service_time" in self.kwargs:
+            calculate_service_time=self.kwargs["calculate_service_time"]
         url = self.base_url + url
         headers = headers or {}
         if params:
@@ -176,7 +181,6 @@ def perform_request(  # type: ignore
             body = self._gzip_compress(body)
             headers["content-encoding"] = "gzip"  # type: ignore
 
-        start = time.time()
         request = requests.Request(method=method, headers=headers, url=url, data=body)
         prepared_request = self.session.prepare_request(request)
         settings = self.session.merge_environment_settings(
@@ -187,6 +191,7 @@ def perform_request(  # type: ignore
             "allow_redirects": allow_redirects,
         }
         send_kwargs.update(settings)
+        start = time.time()
         try:
             response = self.session.send(prepared_request, **send_kwargs)
             duration = time.time() - start
@@ -194,6 +199,7 @@ def perform_request(  # type: ignore
         except reraise_exceptions:
             raise
         except Exception as e:
+            duration = time.time() - start
             self.log_request_fail(
                 method,
                 url,
@@ -207,7 +213,11 @@ def perform_request(  # type: ignore
             if isinstance(e, requests.Timeout):
                 raise ConnectionTimeout("TIMEOUT", str(e), e)
             raise ConnectionError("N/A", str(e), e)
-
+        
+        # Add the service time to the raw_data
+        if calculate_service_time:
+            raw_data = raw_data.rstrip()[:-1] + f', "__client": {{"Service_Time": "{duration}"}}' + '}'
+            
         # raise warnings if any from the 'Warnings' header.
         warnings_headers = (
             (response.headers["warning"],) if "warning" in response.headers else ()