Split server in smaller modules

src/event_dispatcher.cpp

@@ -0,0 +1,77 @@
+#include "event_dispatcher.hpp"
+
+#include <duckdb.hpp>
+
+#define CPPHTTPLIB_OPENSSL_SUPPORT
+#include "httplib.hpp"
+
+namespace httplib = duckdb_httplib_openssl;
+
+// Chosen to be no more than half of the lesser of the two limits:
+//  - The default httplib thread pool size = 8
+//  - The browser limit on the number of server-sent event connections = 6
+#define MAX_EVENT_WAIT_COUNT 3
+
+namespace duckdb {
+namespace ui {
+// An empty Server-Sent Events message. See
+// https://html.spec.whatwg.org/multipage/server-sent-events.html#authoring-notes
+constexpr const char *EMPTY_SSE_MESSAGE = ":\r\r";
+constexpr idx_t EMPTY_SSE_MESSAGE_LENGTH = 3;
+
+bool EventDispatcher::WaitEvent(httplib::DataSink *sink) {
+  std::unique_lock<std::mutex> lock(mutex);
+  // Don't allow too many simultaneous waits, because each consumes a thread in
+  // the httplib thread pool, and also browsers limit the number of server-sent
+  // event connections.
+  if (closed || wait_count >= MAX_EVENT_WAIT_COUNT) {
+    return false;
+  }
+  int target_id = next_id;
+  wait_count++;
+  cv.wait_for(lock, std::chrono::seconds(5));
+  wait_count--;
+  if (closed) {
+    return false;
+  }
+  if (current_id == target_id) {
+    sink->write(message.data(), message.size());
+  } else {
+    // Our wait timer expired. Write an empty, no-op message.
+    // This enables detecting when the client is gone.
+    sink->write(EMPTY_SSE_MESSAGE, EMPTY_SSE_MESSAGE_LENGTH);
+  }
+  return true;
+}
+
+void EventDispatcher::SendEvent(const std::string &_message) {
+  std::lock_guard<std::mutex> guard(mutex);
+  if (closed) {
+    return;
+  }
+
+  current_id = next_id++;
+  message = _message;
+  cv.notify_all();
+}
+
+void EventDispatcher::SendConnectedEvent(const std::string &token) {
+  SendEvent(StringUtil::Format("event: ConnectedEvent\ndata: %s\n\n", token));
+}
+
+void EventDispatcher::SendCatalogChangedEvent() {
+  SendEvent("event: CatalogChangeEvent\ndata:\n\n");
+}
+
+void EventDispatcher::Close() {
+  std::lock_guard<std::mutex> guard(mutex);
+  if (closed) {
+    return;
+  }
+
+  current_id = next_id++;
+  closed = true;
+  cv.notify_all();
+}
+} // namespace ui
+} // namespace duckdb