HHVM does not appear to raise an error if the remote connection is closed and will never fail the pending write. stream_socket_get_name() appears to be a reliable way to detect the closed remote connection.

Author: lucasnetau

src/Query/TcpTransportExecutor.php

@@ -337,24 +337,28 @@ public function handleWritable()
             $written = \fwrite($this->socket, $this->writeBuffer);
         }
 
-        \restore_error_handler();
-
-        // Only report errors if *nothing* could be sent and an error has been raised.
+        // Only report errors if *nothing* could be sent and an error has been raised, or we are unable to retrieve the remote socket name (connection dead) [HHVM].
         // Ignore non-fatal warnings if *some* data could be sent.
         // Any hard (permanent) error will fail to send any data at all.
         // Sending excessive amounts of data will only flush *some* data and then
         // report a temporary error (EAGAIN) which we do not raise here in order
         // to keep the stream open for further tries to write.
         // Should this turn out to be a permanent error later, it will eventually
         // send *nothing* and we can detect this.
-        if (($written === false || $written === 0) && $errstr !== null) {
-            $this->closeError(
-                'Unable to send query to DNS server ' . $this->nameserver . ' (' . $errstr . ')',
-                $errno
-            );
-            return;
+        if (($written === false || $written === 0)) {
+            $name = @\stream_socket_get_name($this->socket, true);
+            if (!is_string($name) || $errstr !== null) {
+                \restore_error_handler();
+                $this->closeError(
+                    'Unable to send query to DNS server ' . $this->nameserver . ' (' . $errstr . ')',
+                    $errno
+                );
+                return;
+            }
         }
 
+        \restore_error_handler();
+
         if (false === $written) {
             return;
         } elseif (isset($this->writeBuffer[$written])) {