Wait for http request completion with condition variable (#1524)

Author: pifopi

include/dpp/queues.h

@@ -30,6 +30,7 @@
 #include <vector>
 #include <functional>
 #include <atomic>
+#include <condition_variable>		
 #include <dpp/httpsclient.h>
 
 namespace dpp {
@@ -240,6 +241,22 @@ class DPP_EXPORT http_request {
 	 */
 	std::unique_ptr<https_client> cli;
 
+	/**
+	 * @brief Mutex for this_captured_signal and this_captured
+	 */
+	std::mutex this_captured_mutex;
+
+	/**
+	 * @brief Condition variable to signal this is no longer captured by an ongoing lambda
+	 */
+	std::condition_variable this_captured_signal;
+
+
+	/**
+	 * @brief True if this is currently captured in a lambda and cannot be deleted
+	 */
+	bool this_captured{false};
+
 public:
 	/**
 	 * @brief Endpoint name

src/dpp/queues.cpp

@@ -107,7 +107,10 @@ http_request::http_request(const std::string &_url, http_completion_event comple
 {
 }
 
-http_request::~http_request()  = default;
+http_request::~http_request() {
+	std::unique_lock<std::mutex> lock(this_captured_mutex);
+	this_captured_signal.wait(lock, [this] { return !this_captured; });
+}
 
 void http_request::complete(const http_request_completion_t &c) {
 	if (complete_handler) {
@@ -260,6 +263,10 @@ http_request_completion_t http_request::run(request_concurrency_queue* processor
 				processor->buckets[this->endpoint] = newbucket;
 
 				/* Transfer it to completed requests */
+				{
+					std::lock_guard<std::mutex> lock(this_captured_mutex);
+					this_captured = true;
+				}
 				owner->queue_work(0, [owner, this, result, hci, _url]() {
 					try {
 						complete(result);
@@ -271,6 +278,11 @@ http_request_completion_t http_request::run(request_concurrency_queue* processor
 						owner->log(ll_error, "Uncaught exception thrown in HTTPS callback for " + std::string(request_verb[method]) + " "  + hci.hostname + ":" + std::to_string(hci.port) + _url + ": <non exception value>");
 					}
 					completed = true;
+					{
+						std::lock_guard<std::mutex> lock(this_captured_mutex);
+						this_captured = false;
+					}
+					this_captured_signal.notify_all();
 				});
 			}
 		);