java - Understanding Server-sent Events -

i'm trying update html5 table in real-time data database. here code:

html page:

<script type="text/javascript">     //check browser support     if(typeof(eventsource)!=="undefined") {         //create object, passing name , location of server side script         var esource = new eventsource("[some address]/api/sse");         //detect message receipt         esource.onmessage = function(event) {             //write received data page              document.getelementbyid("placeholder").innerhtml=table;          };     }     else {         [erro message]     } </script> 

and java restful service:

@path("/sse")    public class sseresource {    @context    private uriinfo context;     public sseresource() {    }     @get    @produces(ssefeature.server_sent_events)    public string getserversentevents() throws exception {         someobject o = new someobject();             final string mystring = o.somequery().getentity().tostring();             return "data: " + mystring + "\n\n";    } } 

this somequery() method queries database , returns want put on table. everythings looks great. want know if it's right or wrong, because if put log on somequery() method, see every 3 seconds query executed. may cause heavy duty, right? normal or code wrong?