fix(proxy-wasm) cancel dispatches when immediately producing a response

Delete the posted event for dispatches that were sent in the latest
Proxy-Wasm step.

src/http/proxy_wasm/ngx_http_proxy_wasm_dispatch.c

@@ -387,6 +387,8 @@ ngx_http_proxy_wasm_dispatch(ngx_proxy_wasm_exec_t *pwexec,
 
     ngx_post_event(ev, &ngx_posted_events);
 
+    call->ev = ev;
+
     ngx_queue_insert_head(&pwexec->calls, &call->q);
 
     ngx_proxy_wasm_ctx_set_next_action(pwctx, NGX_PROXY_WASM_ACTION_PAUSE);
@@ -427,6 +429,12 @@ ngx_http_proxy_wasm_dispatch_destroy(ngx_http_proxy_wasm_dispatch_t *call)
 
     dd("enter");
 
+    if (call->ev) {
+        ngx_delete_posted_event(call->ev);
+        ngx_free(call->ev);
+        call->ev = NULL;
+    }
+
     ngx_wasm_socket_tcp_destroy(sock);
 
     if (call->host.data) {
@@ -461,6 +469,7 @@ ngx_http_proxy_wasm_dispatch_handler(ngx_event_t *ev)
     ngx_wasm_socket_tcp_t           *sock = &call->sock;
 
     ngx_free(ev);
+    call->ev = NULL;
 
     sock->resume_handler = ngx_http_proxy_wasm_dispatch_resume_handler;
     sock->data = call;

src/http/proxy_wasm/ngx_http_proxy_wasm_dispatch.h

@@ -49,6 +49,8 @@ struct ngx_http_proxy_wasm_dispatch_s {
     ngx_chain_t                            *req_body;
     ngx_chain_t                            *req_out;
 
+    ngx_event_t                            *ev;    /* initial posted event */
+
     ngx_wasm_http_reader_ctx_t              http_reader;
     ngx_http_proxy_wasm_dispatch_state_e    state;
     ngx_http_request_t                      fake_r;

t/03-proxy_wasm/hfuncs/133-proxy_dispatch_http_edge_cases.t

@@ -427,3 +427,29 @@ qr/\A\[error] .*? dispatch failed: tcp socket - Connection refused
 [crit]
 [emerg]
 [alert]
+
+
+
+=== TEST 13: proxy_wasm - dispatch_http_call() followed by a local response
+Cancels posted events of pending dispatches
+--- skip_no_debug
+--- valgrind
+--- load_nginx_modules: ngx_http_echo_module
+--- wasm_modules: hostcalls
+--- config
+    location /t {
+        proxy_wasm hostcalls 'on=request_headers \
+                              test=/t/dispatch_and_local_response \
+                              host=127.0.0.1:1';
+        echo_status 200;
+    }
+--- error_code: 201
+--- response_body
+--- grep_error_log eval: qr/proxy_wasm http dispatch cancelled/
+--- grep_error_log_out
+proxy_wasm http dispatch cancelled
+proxy_wasm http dispatch cancelled
+--- no_error_log
+[crit]
+[emerg]
+[alert]

t/lib/proxy-wasm-tests/hostcalls/src/types/test_http.rs

@@ -107,6 +107,13 @@ impl TestHttp {
                 return Action::Pause;
             }
 
+            /* edge case: dispatch + local response */
+            "/t/dispatch_and_local_response" => {
+                self.send_http_dispatch(0);
+                self.send_http_dispatch(0);
+                test_send_status(self, 201)
+            }
+
             /* shared memory */
             "/t/shm/get_shared_data" => test_get_shared_data(self),
             "/t/shm/set_shared_data" => test_set_shared_data(self),