php - server sent events while loop takes so much time for page load, when page is refreshed or F5 is pressed -

i using server sent events query database new records , display events user

here code

javascript

window.onload = function setdatasource() {  if (!!window.eventsource) { var source = new eventsource("polling.php");  source.addeventlistener("message", function(e) {   console.log(e.data); }, false);  source.addeventlistener("open", function(e) {   console.log("opened"); }, false);  source.addeventlistener("error", function(e) {   console.log(e);   if (e.readystate == eventsource.closed) {     console.log("closed");   } }, false); } else {}} 

php

  <?php   header("content-type: text/event-stream\n\n");   include_once dirname(__file__) . '/db.php';   session_start();     while (1) {    $response = getnewmessages();    echo 'data: message '. json_encode1($response)."\n\n";    ob_flush();    flush();    sleep(5);     }   function getnewmessages () { // query database , new records.  } 

it works fine , gets new records every 5 seconds. problem here when refresh page manually,it takes time page load.

when page loading, can figure out while loop still executes (at least thrice) , pauses page. after time page starts loading normally. doubt while loop pausing execution

can please suggest me how overcome situation ? or how can replace while loop?

two problems: 1. php file-based sessions lock session file while it's in use 2. php cannot detect client has disconnected until after tries output

so, worst case, refresh script runs, dumps out updates, , sleeps 5 seconds. if client refreshes @ exact same moment, take 5 loop iteration occur, , output produced, allowing php realize connection's closed.

quick fix: session_write_close() release lock on session file, allowing parallel requests occur.

long term fix: use better polling loop check messages, e.g. websockets.