Fix crash when HTTP pipeline data arrives during async response writing

http/server/HttpHandler.cpp

@@ -86,6 +86,11 @@ bool HttpHandler::Init(int http_version) {
         tid = hv_gettid();
     }
     parser->InitRequest(req.get());
+    hookHttpCb();
+    return true;
+}
+
+void HttpHandler::hookHttpCb() {
     // NOTE: hook http_cb
     req->http_cb = [this](HttpMessage* msg, http_parser_state state, const char* data, size_t size) {
         if (this->state == WANT_CLOSE) return;
@@ -105,23 +110,42 @@ bool HttpHandler::Init(int http_version) {
             break;
         }
     };
-    return true;
 }
 
 void HttpHandler::Reset() {
     state = WANT_RECV;
     error = 0;
-    req->Reset();
-    resp->Reset();
+    // Create new request/response to avoid race condition with async handlers
+    // that may still hold shared_ptr references to the old req/resp objects.
+    // This prevents crashes when HTTP pipeline data arrives while an async
+    // response is still being written.
+    req  = std::make_shared<HttpRequest>();
+    resp = std::make_shared<HttpResponse>();
+    if (protocol == HTTP_V2) {
+        resp->http_major = req->http_major = 2;
+        resp->http_minor = req->http_minor = 0;
+    }
     ctx = NULL;
     api_handler = NULL;
     closeFile();
     if (writer) {
-        writer->Begin();
+        // Retire old writer: mark DISCONNECTED and clear io_ so that
+        // ~Channel() won't close the hio_t when the async handler's
+        // shared_ptr reference is eventually released, and any
+        // further write attempts through the old writer fail gracefully.
+        writer->status = hv::SocketChannel::DISCONNECTED;
+        writer->io_ = NULL;
         writer->onwrite = NULL;
         writer->onclose = NULL;
     }
+    if (io) {
+        writer = std::make_shared<HttpResponseWriter>(io, resp);
+        writer->status = hv::SocketChannel::CONNECTED;
+    } else {
+        writer = NULL;
+    }
     parser->InitRequest(req.get());
+    hookHttpCb();
 }
 
 void HttpHandler::Close() {

http/server/HttpHandler.h

@@ -149,6 +149,7 @@ class HttpHandler {
     void  addResponseHeaders();
 
     // http_cb
+    void hookHttpCb();
     void onHeadersComplete();
     void onBody(const char* data, size_t size);
     void onMessageComplete();