Add requestsBufferSize function (#2124)

examples/client_example/main.cc

@@ -72,6 +72,8 @@ int main()
                     std::cout << "count=" << nth_resp << std::endl;
                 });
         }
+        std::cout << "requestsBufferSize:" << client->requestsBufferSize()
+                  << std::endl;
     }
 
     app().run();

lib/inc/drogon/HttpClient.h

@@ -21,6 +21,7 @@
 #include <drogon/HttpRequest.h>
 #include <trantor/utils/NonCopyable.h>
 #include <trantor/net/EventLoop.h>
+#include <cstddef>
 #include <functional>
 #include <memory>
 #include <future>
@@ -178,6 +179,12 @@ class DROGON_EXPORT HttpClient : public trantor::NonCopyable
      */
     virtual void setSockOptCallback(std::function<void(int)> cb) = 0;
 
+    /**
+     * @brief Return the number of unsent http requests in the current http
+     * client cache buffer
+     */
+    virtual std::size_t requestsBufferSize() = 0;
+
     /// Set the pipelining depth, which is the number of requests that are not
     /// responding.
     /**

lib/src/HttpClientImpl.h

@@ -19,6 +19,9 @@
 #include <trantor/net/EventLoop.h>
 #include <trantor/net/Resolver.h>
 #include <trantor/net/TcpClient.h>
+#include <cstddef>
+#include <functional>
+#include <future>
 #include <list>
 #include <mutex>
 #include <queue>
@@ -115,6 +118,21 @@ class HttpClientImpl final : public HttpClient,
         sockOptCallback_ = std::move(cb);
     }
 
+    std::size_t requestsBufferSize() override
+    {
+        if (loop_->isInLoopThread())
+        {
+            return requestsBuffer_.size();
+        }
+        else
+        {
+            std::promise<std::size_t> bufferSize;
+            loop_->queueInLoop(
+                [&] { bufferSize.set_value(requestsBuffer_.size()); });
+            return bufferSize.get_future().get();
+        }
+    }
+
   private:
     std::shared_ptr<trantor::TcpClient> tcpClientPtr_;
     trantor::EventLoop *loop_;