CODEWITHSUNDEEP
apigoogle-chrome-extensionxmlhttprequest
user3081557
user3081557

Reputation: 125

Opening chrome should cause the extension to check the output of an API.How can this be possible?

Hi I am developing a website as my chrome extension.the extension periodically checks the output of a server file and then works according to the output of the server file.Now what I need is that presently it checks the output of the server file every 5 min.So what I need is that when the output of the server file changes at any time,at that moment I have to do some operations.How can I do this? Here is my background.js

var myNotificationID = null;
var oldChromeVersion = !chrome.runtime;
chrome.windows.onCreated.addListener(function (){ 
 updateIcon();
 });
chrome.tabs.onCreated.addListener(function (){ 
 updateIcon();
    });
    chrome.tabs.onUpdated.addListener(function (){ 
      updateIcon();
    });
 function getGmailUrl() {
  return "http://calpinemate.com/";
}

function isGmailUrl(url) {
  return url.indexOf(getGmailUrl()) == 0;
}
 chrome.windows.onCreated.addListener(function (){ 
  updateIcon();
   });
function onInit() {
  updateIcon();
  if (!oldChromeVersion) { 
    chrome.alarms.create('watchdog',{periodInMinutes:5,delayInMinutes:  0});
  }
}

function onAlarm(alarm) {
  if (alarm && alarm.name == 'watchdog') {
    onWatchdog();
  } 
  else {
    updateIcon();
  }
}

function onWatchdog() {
  chrome.alarms.get('refresh', function(alarm) {
  if (alarm) {
    console.log('Refresh alarm exists. Yay.');
  } 
  else {
    updateIcon();  
  }
});
}
if (oldChromeVersion) {
  updateIcon();
  onInit();
} 
else {
 chrome.runtime.onInstalled.addListener(onInit);
 chrome.alarms.onAlarm.addListener(onAlarm);
 }

It is the updateIcon() which reads the server file.And when there is change in the output of server file,I have to call the updateIcon() itself.Presently only in every 5 min,the output is checked and updated in extension.But I need it to happen at the moment the status of server file changes.Anyone please help me. In short,what I need is that when the output of API changes at any time at that time I have to call updateIcon().

Here is my updateIcon()

function updateIcon(){
  var urlPrefix = 'http://www.calpinemate.com/employees/attendanceStatus/';
  var urlSuffix = '/2';
  var req = new XMLHttpRequest();
  req.addEventListener("readystatechange", function() {
  if (req.readyState == 4) {
    if (req.status == 200) {    
       var item=req.responseText;


       if(item==1){

        .....//something   
      }

      else{
         // do something  
      } 
   else {

        alert("ERROR: status code " + req.status);

       }
      }
       });
    var url = urlPrefix + encodeURIComponent(localStorage.username) + urlSuffix;
    req.open("GET", url);
     req.send(null);     
   }

I need to periodically monitor the API for output.

Upvotes: 0

Views: 186

Answers (1)

gkalpak
gkalpak

Reputation: 48211

You could use a WebSocket to maintain a persistent, two-way channel between the server and your extension.

But, considering that PHP does not have native support for WebSockets (i.e. you would need to use an external library) and the fact that the interaction will be infrequent (only at log-in/-out), it might be unnecessary overhead.

I suggest you communicate the login-status directly from your web-page to your extension. For a more detailed description of the process, see my answer to one similar question of yours.

UPDATE:
Since it turned out you don't have control of the domain you need to "monitor", there is unfortunately no other option (that I know of) than polling at frequent intervals on that server-resource.

If you are using a non-persistent background-page (which is advisable due to its resource-friendliness) you must use the chrome.alarms API, which allows at most 1 triggering per minute: (in order to reduce the load on the user's machine - note: to help debug your extension, this limit is no imposed on unpacked extensions).

If you decide to use a persistent background-page, you can use setInterval() with an arbitrarily smal period (in milliseconds):

setInterval(function() {
    /* Check up on the server */
    ...
}, 30000);   // <-- trigger every 30.000 milliseconds (== 30 seconds)

Upvotes: 3

Related Questions