Optimize UDP buffer and WSGI/ASGI defaults

- Replace list with deque for UDP datagram buffer to get O(1) popleft
  instead of O(n) pop(0) operations
- Define WSGI/ASGI environ/scope defaults as compile-time constants
  to avoid map allocation on each request

Author: benoitc

priv/erlang_loop.py

@@ -1208,7 +1208,7 @@ def __init__(self, loop, sock, protocol, address=None, extra=None):
         self._sock = sock
         self._protocol = protocol
         self._address = address  # Default remote address (for connected UDP)
-        self._buffer = []  # List of (data, addr) tuples
+        self._buffer = deque()  # Deque of (data, addr) tuples for O(1) popleft
         self._closing = False
         self._conn_lost = 0
         self._fileno = sock.fileno()  # Cache fileno to avoid repeated calls
@@ -1286,14 +1286,14 @@ def _write_ready(self):
             except (BlockingIOError, InterruptedError):
                 return
             except OSError as exc:
-                self._buffer.pop(0)
+                self._buffer.popleft()
                 self._protocol.error_received(exc)
                 return
             except Exception as exc:
                 self._fatal_error(exc, 'Fatal write error on datagram transport')
                 return
 
-            self._buffer.pop(0)
+            self._buffer.popleft()
 
         self._loop.remove_writer(self._fileno)
         if self._closing:

src/py_asgi.erl

@@ -64,6 +64,20 @@
     scope_opts/0
 ]).
 
+%% Pre-defined ASGI scope defaults (compile-time constant for zero allocation)
+%% Note: raw_path is set dynamically based on path in ensure_scope_defaults/1
+-define(ASGI_SCOPE_DEFAULTS, #{
+    type => <<"http">>,
+    asgi => #{<<"version">> => <<"3.0">>, <<"spec_version">> => <<"2.3">>},
+    http_version => <<"1.1">>,
+    method => <<"GET">>,
+    scheme => <<"http">>,
+    query_string => <<>>,
+    root_path => <<>>,
+    headers => [],
+    state => #{}
+}).
+
 %% ASGI scope dictionary.
 -type scope() :: #{
     type := binary(),
@@ -149,18 +163,13 @@ build_scope(Scope, Opts) ->
 %%% ============================================================================
 
 %% @private
-%% Ensure all required ASGI scope fields have defaults
+%% Ensure all required ASGI scope fields have defaults.
+%% Uses compile-time constant ?ASGI_SCOPE_DEFAULTS to avoid
+%% map allocation on each request.
 ensure_scope_defaults(Scope) ->
-    Defaults = #{
-        type => <<"http">>,
-        asgi => #{<<"version">> => <<"3.0">>, <<"spec_version">> => <<"2.3">>},
-        http_version => <<"1.1">>,
-        method => <<"GET">>,
-        scheme => <<"http">>,
-        raw_path => maps:get(path, Scope, <<"/">>),
-        query_string => <<>>,
-        root_path => <<>>,
-        headers => [],
-        state => #{}
-    },
-    maps:merge(Defaults, Scope).
+    %% raw_path defaults to path if not provided
+    WithRawPath = case maps:is_key(raw_path, Scope) of
+        true -> Scope;
+        false -> Scope#{raw_path => maps:get(path, Scope, <<"/">>)}
+    end,
+    maps:merge(?ASGI_SCOPE_DEFAULTS, WithRawPath).

src/py_wsgi.erl

@@ -57,6 +57,22 @@
     environ/0
 ]).
 
+%% Pre-defined WSGI environ defaults (compile-time constant for zero allocation)
+-define(WSGI_ENVIRON_DEFAULTS, #{
+    <<"REQUEST_METHOD">> => <<"GET">>,
+    <<"SCRIPT_NAME">> => <<>>,
+    <<"PATH_INFO">> => <<"/">>,
+    <<"QUERY_STRING">> => <<>>,
+    <<"SERVER_NAME">> => <<"localhost">>,
+    <<"SERVER_PORT">> => <<"80">>,
+    <<"SERVER_PROTOCOL">> => <<"HTTP/1.1">>,
+    <<"wsgi.version">> => {1, 0},
+    <<"wsgi.url_scheme">> => <<"http">>,
+    <<"wsgi.multithread">> => true,
+    <<"wsgi.multiprocess">> => true,
+    <<"wsgi.run_once">> => false
+}).
+
 %% WSGI environ dictionary.
 -type environ() :: #{
     binary() => binary() | integer() | atom()
@@ -100,20 +116,8 @@ run(Module, Callable, Environ, Opts) ->
 %%% ============================================================================
 
 %% @private
-%% Ensure all required WSGI environ fields have defaults
+%% Ensure all required WSGI environ fields have defaults.
+%% Uses compile-time constant ?WSGI_ENVIRON_DEFAULTS to avoid
+%% map allocation on each request.
 ensure_environ_defaults(Environ) ->
-    Defaults = #{
-        <<"REQUEST_METHOD">> => <<"GET">>,
-        <<"SCRIPT_NAME">> => <<>>,
-        <<"PATH_INFO">> => <<"/">>,
-        <<"QUERY_STRING">> => <<>>,
-        <<"SERVER_NAME">> => <<"localhost">>,
-        <<"SERVER_PORT">> => <<"80">>,
-        <<"SERVER_PROTOCOL">> => <<"HTTP/1.1">>,
-        <<"wsgi.version">> => {1, 0},
-        <<"wsgi.url_scheme">> => <<"http">>,
-        <<"wsgi.multithread">> => true,
-        <<"wsgi.multiprocess">> => true,
-        <<"wsgi.run_once">> => false
-    },
-    maps:merge(Defaults, Environ).
+    maps:merge(?WSGI_ENVIRON_DEFAULTS, Environ).