From d464e4beb423881e49313aa432474d9e71ff0460 Mon Sep 17 00:00:00 2001
From: szeka9 <szkalman79@gmail.com>
Date: Tue, 24 Mar 2026 23:39:55 +0100
Subject: [PATCH] Add new exception for server busy state

Allow applications to indicate busy state
by raising ServerBusyError, resulting in 503.
---
 src/pyrobusta/bindings/socket_http.py |  6 +++-
 src/pyrobusta/protocol/http.py        |  6 ++++
 tests/functional/test_http.py         | 42 +++++++++++++++++++++++++--
 3 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/src/pyrobusta/bindings/socket_http.py b/src/pyrobusta/bindings/socket_http.py
index d1c51ec..955ba3b 100644
--- a/src/pyrobusta/bindings/socket_http.py
+++ b/src/pyrobusta/bindings/socket_http.py
@@ -8,7 +8,7 @@
 
 from ..stream.buffer import MemoryPool, SlidingBuffer, BufferFullError
 from ..transport.socket import SocketBase
-from ..protocol.http import HttpEngine
+from ..protocol.http import HttpEngine, ServerBusyError
 from ..utils.config import get_config
 from ..utils import logging
 
@@ -153,6 +153,10 @@ async def _run_state_machine(self):
             self._engine.on_failure(self._send_buf, b"Buffer full")
             await self._flush_response()
             return
+        except ServerBusyError:
+            self._engine.on_busy(self._send_buf)
+            await self._flush_response()
+            return
         except Exception as e:  # pylint: disable=W0718
             logging.warning(f"[SocketHttp] error in _run_state_machine: {e}")
             self._engine.on_failure(self._send_buf, str(e).encode("ascii"))
diff --git a/src/pyrobusta/protocol/http.py b/src/pyrobusta/protocol/http.py
index eb324a1..ddd9127 100644
--- a/src/pyrobusta/protocol/http.py
+++ b/src/pyrobusta/protocol/http.py
@@ -16,6 +16,12 @@ class HeaderParsingError(ValueError):
     pass
 
 
+class ServerBusyError(RuntimeError):
+    """Exception for applications to indicate busy state"""
+
+    pass
+
+
 class HttpEngine:
     """
     HTTP protocol parser state machine
diff --git a/tests/functional/test_http.py b/tests/functional/test_http.py
index a491d3e..76b084a 100644
--- a/tests/functional/test_http.py
+++ b/tests/functional/test_http.py
@@ -3,7 +3,11 @@
 
 from pyrobusta.server import http_server
 from pyrobusta.protocol import http_multipart
-from pyrobusta.protocol.http import HttpEngine, enable_optional_features
+from pyrobusta.protocol.http import (
+    HttpEngine,
+    enable_optional_features,
+    ServerBusyError,
+)
 from pyrobusta.utils import config
 
 #################################################
@@ -20,7 +24,7 @@ def test_assert(name, actual, expected):
         raise AssertionError(f"{actual} != {expected}")
 
 
-async def send_request(request, tls):
+async def send_request(request, tls=False):
     port = (
         http_server.HttpServer.LISTEN_PORT_HTTPS
         if tls
@@ -80,6 +84,11 @@ def multipart_callback(headers, body):
     return "multipart/form-data", ("text/plain", multipart_response(part_count))
 
 
+@HttpEngine.route("/test/busy", "POST")
+def busy_callback(headers, body):
+    raise ServerBusyError()
+
+
 async def test_simple_response(tls_enabled):
     setup_config(multipart=False, tls_enabled=tls_enabled)
 
@@ -164,6 +173,27 @@ async def test_multipart_response(tls_enabled):
     await server.terminate()
 
 
+async def test_server_busy():
+    setup_config()
+
+    server = http_server.HttpServer()
+    server_task = asyncio.create_task(server.run_server())
+    await asyncio.sleep_ms(100)
+
+    # Test: 1 part
+    plain_response = await send_request(
+        b"POST /test/busy HTTP/1.1\r\n" b"Host: localhost\r\n\r\n"
+    )
+    test_assert(
+        f"response is rejected by busy service with 503",
+        b"503 Service Unavailable" in plain_response,
+        True,
+    )
+
+    server_task.cancel()
+    await server.terminate()
+
+
 #################################################
 # Test methods
 #################################################
@@ -190,6 +220,12 @@ def test_registration():
         HttpEngine.ENDPOINTS[b"/test/multipart"][b"GET"],
     )
 
+    test_assert(
+        "busy endpoint registration",
+        busy_callback,
+        HttpEngine.ENDPOINTS[b"/test/busy"][b"POST"],
+    )
+
 
 def test_multipart_patches():
     setup_config(multipart=True)
@@ -209,5 +245,7 @@ def test_main():
     asyncio.run(test_multipart_response(tls_enabled=False))
     asyncio.run(test_multipart_response(tls_enabled=True))
 
+    asyncio.run(test_server_busy())
+
 
 test_main()