To make AJAX call from Kibana Visualization to external web service.

 $.ajax({
     type: "GET",
     url: 'http://localhost/es',
     headers: {'Content-Type':'application/x-www-form-urlencoded'},
     success: function(my_result) {
          console.log(my_result);
     },
     error: function() {
          alert("error1");
     },
});

There are two separate headers that are necessary here: access-control-allow-origin and access-control-allow-headers. You’re currently setting access-control-allow-origin but I don’t see anywhere you’re setting access-control-allow-headers.