Python: Add ASGI lifespan state support.

Lifespan state is a special dict in asgi lifespan scope, which allow
applications to persist data from the lifespan cycle to request/response
handling. The scope["state"] namespace provides a place to store these
sorts of things. The server will ensure that a shallow copy of the
namespace is passed into each subsequent request/response call into the
application.

Some frameworks are already taking advantage of this feature, for
example, starlette, and without this feature they wouldn't work
properly.

Signed-off-by: synodriver <diguohuangjiajinweijun@gmail.com>
Reviewed-by: Andrew Clayton <a.clayton@nginx.com>
[ Minor code tweaks to avoid lines > 80 chars, static a function and
  re-work the PyMemberDef structure initialisation for Python <3.7
  and -Wwrite-strings compatibility - Andrew ]
Tested-by: <https://github.com/synodriver>
Tested-by: <https://github.com/hawiliali>
Closes: <https://github.com/nginx/unit/issues/864>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

src/python/nxt_python_asgi.c

@@ -450,6 +450,7 @@ static void
 nxt_py_asgi_request_handler(nxt_unit_request_info_t *req)
 {
     PyObject                *scope, *res, *task, *receive, *send, *done, *asgi;
+    PyObject                *state, *newstate, *lifespan;
     PyObject                *stage2;
     nxt_python_target_t     *target;
     nxt_py_asgi_ctx_data_t  *ctx_data;
@@ -493,15 +494,41 @@ nxt_py_asgi_request_handler(nxt_unit_request_info_t *req)
     }
 
     req->data = asgi;
+    ctx_data = req->ctx->data;
     target = &nxt_py_targets->target[req->request->app_target];
-
-    scope = nxt_py_asgi_create_http_scope(req, target);
-    if (nxt_slow_path(scope == NULL)) {
+    lifespan = ctx_data->target_lifespans[req->request->app_target];
+    state = PyObject_GetAttr(lifespan, nxt_py_state_str);
+    if (nxt_slow_path(state == NULL)) {
+        nxt_unit_req_alert(req, "Python failed to get 'state' attribute");
         nxt_unit_request_done(req, NXT_UNIT_ERROR);
 
         goto release_done;
     }
 
+    newstate = PyDict_Copy(state);
+    if (nxt_slow_path(newstate == NULL)) {
+        nxt_unit_req_alert(req, "Python failed to call state.copy()");
+        nxt_unit_request_done(req, NXT_UNIT_ERROR);
+        Py_DECREF(state);
+        goto release_done;
+    }
+    Py_DECREF(state);
+
+    scope = nxt_py_asgi_create_http_scope(req, target);
+    if (nxt_slow_path(scope == NULL)) {
+        nxt_unit_request_done(req, NXT_UNIT_ERROR);
+        Py_DECREF(newstate);
+        goto release_done;
+    }
+
+    if (nxt_slow_path(PyDict_SetItem(scope, nxt_py_state_str, newstate)
+                      == -1))
+    {
+        Py_DECREF(newstate);
+        goto release_scope;
+    }
+    Py_DECREF(newstate);
+
     if (!target->asgi_legacy) {
         nxt_unit_req_debug(req, "Python call ASGI 3.0 application");
 
@@ -555,7 +582,6 @@ nxt_py_asgi_request_handler(nxt_unit_request_info_t *req)
         goto release_scope;
     }
 
-    ctx_data = req->ctx->data;
 
     task = PyObject_CallFunctionObjArgs(ctx_data->loop_create_task, res, NULL);
     if (nxt_slow_path(task == NULL)) {

src/python/nxt_python_asgi_lifespan.c

@@ -12,6 +12,8 @@
 #include <python/nxt_python_asgi.h>
 #include <python/nxt_python_asgi_str.h>
 
+#include <structmember.h>
+
 
 typedef struct  {
     PyObject_HEAD
@@ -25,6 +27,7 @@ typedef struct  {
     PyObject                *startup_future;
     PyObject                *shutdown_future;
     PyObject                *receive_future;
+    PyObject                *state;
 } nxt_py_asgi_lifespan_t;
 
 static PyObject *nxt_py_asgi_lifespan_target_startup(
@@ -41,6 +44,7 @@ static PyObject *nxt_py_asgi_lifespan_send_shutdown(
     nxt_py_asgi_lifespan_t *lifespan, int v, PyObject *dict);
 static PyObject *nxt_py_asgi_lifespan_disable(nxt_py_asgi_lifespan_t *lifespan);
 static PyObject *nxt_py_asgi_lifespan_done(PyObject *self, PyObject *future);
+static void nxt_py_asgi_lifespan_dealloc(PyObject *self);
 
 
 static PyMethodDef nxt_py_asgi_lifespan_methods[] = {
@@ -50,6 +54,26 @@ static PyMethodDef nxt_py_asgi_lifespan_methods[] = {
     { NULL, NULL, 0, 0 }
 };
 
+static PyMemberDef nxt_py_asgi_lifespan_members[] = {
+    {
+#if PY_VERSION_HEX >= NXT_PYTHON_VER(3, 7)
+        .name   = "state",
+#else
+        .name   = (char *)"state",
+#endif
+        .type   = T_OBJECT_EX,
+        .offset = offsetof(nxt_py_asgi_lifespan_t, state),
+        .flags  = READONLY,
+#if PY_VERSION_HEX >= NXT_PYTHON_VER(3, 7)
+        .doc    = PyDoc_STR("lifespan.state")
+#else
+        .doc    = (char *)PyDoc_STR("lifespan.state")
+#endif
+    },
+
+    { NULL, 0, 0, 0, NULL }
+};
+
 static PyAsyncMethods nxt_py_asgi_async_methods = {
     .am_await = nxt_py_asgi_await,
 };
@@ -59,13 +83,14 @@ static PyTypeObject nxt_py_asgi_lifespan_type = {
 
     .tp_name      = "unit._asgi_lifespan",
     .tp_basicsize = sizeof(nxt_py_asgi_lifespan_t),
-    .tp_dealloc   = nxt_py_asgi_dealloc,
+    .tp_dealloc   = nxt_py_asgi_lifespan_dealloc,
     .tp_as_async  = &nxt_py_asgi_async_methods,
     .tp_flags     = Py_TPFLAGS_DEFAULT,
     .tp_doc       = "unit ASGI Lifespan object",
     .tp_iter      = nxt_py_asgi_iter,
     .tp_iternext  = nxt_py_asgi_next,
     .tp_methods   = nxt_py_asgi_lifespan_methods,
+    .tp_members   = nxt_py_asgi_lifespan_members,
 };
 
 
@@ -163,12 +188,29 @@ nxt_py_asgi_lifespan_target_startup(nxt_py_asgi_ctx_data_t *ctx_data,
     lifespan->shutdown_called = 0;
     lifespan->shutdown_future = NULL;
     lifespan->receive_future = NULL;
+    lifespan->state = NULL;
 
     scope = nxt_py_asgi_new_scope(NULL, nxt_py_lifespan_str, nxt_py_2_0_str);
     if (nxt_slow_path(scope == NULL)) {
         goto release_future;
     }
 
+    lifespan->state = PyDict_New();
+    if (nxt_slow_path(lifespan->state == NULL)) {
+        nxt_unit_req_error(NULL,
+                           "Python failed to create 'state' dict");
+        goto release_future;
+    }
+
+    if (nxt_slow_path(PyDict_SetItem(scope, nxt_py_state_str,
+                                     lifespan->state) == -1))
+    {
+        nxt_unit_req_error(NULL,
+                           "Python failed to set 'scope.state' item");
+        Py_CLEAR(lifespan->state);
+        goto release_future;
+    }
+
     if (!target->asgi_legacy) {
         nxt_unit_req_debug(NULL, "Python call ASGI 3.0 application");
 
@@ -604,4 +646,14 @@ nxt_py_asgi_lifespan_done(PyObject *self, PyObject *future)
 }
 
 
+static void
+nxt_py_asgi_lifespan_dealloc(PyObject *self)
+{
+    nxt_py_asgi_lifespan_t *lifespan = (nxt_py_asgi_lifespan_t *)self;
+
+    Py_CLEAR(lifespan->state);
+    PyObject_Del(self);
+}
+
+
 #endif /* NXT_HAVE_ASGI */

src/python/nxt_python_asgi_str.c

@@ -55,6 +55,7 @@ PyObject  *nxt_py_subprotocol_str;
 PyObject  *nxt_py_subprotocols_str;
 PyObject  *nxt_py_text_str;
 PyObject  *nxt_py_type_str;
+PyObject  *nxt_py_state_str;
 PyObject  *nxt_py_version_str;
 PyObject  *nxt_py_websocket_str;
 PyObject  *nxt_py_websocket_accept_str;
@@ -110,6 +111,7 @@ static nxt_python_string_t nxt_py_asgi_strings[] = {
     { nxt_string("subprotocols"), &nxt_py_subprotocols_str },
     { nxt_string("text"), &nxt_py_text_str },
     { nxt_string("type"), &nxt_py_type_str },
+    { nxt_string("state"), &nxt_py_state_str },
     { nxt_string("version"), &nxt_py_version_str },
     { nxt_string("websocket"), &nxt_py_websocket_str },
     { nxt_string("websocket.accept"), &nxt_py_websocket_accept_str },

src/python/nxt_python_asgi_str.h

@@ -50,6 +50,7 @@ extern PyObject  *nxt_py_subprotocol_str;
 extern PyObject  *nxt_py_subprotocols_str;
 extern PyObject  *nxt_py_text_str;
 extern PyObject  *nxt_py_type_str;
+extern PyObject  *nxt_py_state_str;
 extern PyObject  *nxt_py_version_str;
 extern PyObject  *nxt_py_websocket_str;
 extern PyObject  *nxt_py_websocket_accept_str;