fix: reconnect on demand when connection is down at send time

When async_send() finds the connection down, it calls reconnect()
but then unconditionally marks the request as unsent (-1) without
checking if reconnect succeeded. This causes requests to be lost
even when the server is already available.

Now after reconnect(), check isConnected() and fall through to
send if the connection was restored. Also change try_to_lock to
a timed lock (2.5s) so concurrent threads wait for an ongoing
reconnect instead of giving up immediately.

Author: testillano

src/Http2Client.cpp

@@ -124,12 +124,17 @@ void Http2Client::enableMetrics(ert::metrics::Metrics *metrics,
 
 void Http2Client::reconnect()
 {
-    std::unique_lock<std::shared_timed_mutex> lock(mutex_, std::try_to_lock);
+    std::unique_lock<std::shared_timed_mutex> lock(mutex_, std::chrono::milliseconds(2500));
     if (!lock.owns_lock())
     {
         return;
     }
 
+    if (connection_ && connection_->isConnected())
+    {
+        return; // another thread already reconnected
+    }
+
     connection_->reconnect();
 }
 
@@ -153,15 +158,22 @@ void Http2Client::async_send(
 
         reconnect();
 
-        // metrics
-        if (metrics_) {
-            auto& counter = observed_requests_unsents_counter_family_ptr_->Add({{"method", method}});
-            counter.Increment();
-        }
+        if (!connection_ || !connection_->isConnected())
+        {
+            // metrics
+            if (metrics_) {
+                auto& counter = observed_requests_unsents_counter_family_ptr_->Add({{"method", method}});
+                counter.Increment();
+            }
 
-        // Invoke callback
-        cb(Http2Client::response{"", -1});
-        return;
+            // Invoke callback
+            cb(Http2Client::response{"", -1});
+            return;
+        }
+        // Reconnect succeeded: fall through to send
+        LOGINFORMATIONAL(
+            ert::tracing::Logger::informational("Reconnection succeeded, proceeding with request", ERT_FILE_LOCATION);
+        );
     }
 
     // Ignore Body on GET, DELETE and HEAD: