I am developing Appcelerator Titanium Alloy mobile app for Android and iOS. I have a user case where a certain action is performed by other app user which trigger change of object state on server. App is connected with REST api. Then other users should be notified by this change and their app should sync and update app state.
I believed I should be using timers to continuously check the api which inform other users that change has happen on server for state. Once this change is update I shall remove timers...
Is this good approach to use Timers?
thanks
No timers. Should use sockets. I.e. when a change is made on the server, send a message via a web socket to all other users...
If you use timers you will always have to check because you're client will never know when a change happened... And you will waste many trips to the server asking 'anything new?' you can never remove your timer because you don't know when something changed.
Related
I am creating a video/audio calling web app and want to show users an incoming call notification just like it would show in a native calling app
So, is there a way to implement it?
I know I can implement simple push notifications but that is different from what a notification for an incoming call would look like.
when an incoming call comes in a native app, the phone's ringtone starts playing and the notification stays there until the call timeout happens or the user makes an action.
so I need something like that.
I have a nodejs server with a client app
Assuming:
User has allowed notifications on my website.
Service worker is installed and ready.
User sets a client side reminder to be reminded 24 hours from now.
No backend service or server to push the notification to the user.
How can I trigger a desktop notification if there is no backend server to push that notification? Is this possible?
The service worker will be shutdown by the browser if provided a timeout/interval and the web-alarm/task-scheduler specification is not yet ready for use. Is there no client side only approach to trigger a notification at some designated time in the future?
Is there a desktop notification that is strictly not a "push notification"? A push notification, by nature, is pushed from a server. Can a notification be triggered from the client side?
I do not believe this is possible at this point in time.
Push notifications are specified in RFC8030, from its abstract:
This document describes a simple protocol for the delivery of real-
time events to user agents. This scheme uses HTTP/2 server push.
Which implies the requirement for a server supporting HTTP/2 push.
I do love to rant at Javascript, and I do not seem to be able to find an Javascript implementation of an HTTP2 server to run in the browser (there is for node), which is a shame for me, and would be awesome to mock about.
So, looking for fame, http2-server.js is missing.
You might be able to consider using localStorage. However, this is only beneficial for users that utilize the same device and browser.
Below is a function that kicks off on page load. If you want it to occur periodically throughout a session, you could wrap it into a setInterval and check periodically. This is assuming it needs to be exactly 24 hours later to the millisecond.
// on page load
window.onload = () => {
const dayMs = 24*60*60*1000; // 1 day in milliseconds
const notificationTimer = localStorage.getItem('notificationTimer');
if(notificationTimer){
const sendNotification = (Date.now() - (new Date(notificationTimer)).getTime()) > dayMs;
if(sendNotification){
const notification = new Notification('Displaying next day reminder from yesterday');
}
}
};
When the user selects the next day reminder you can then set the notificationTimer:
localStorage.setItem(notificationTimer, Date.now());
You'd have to make some caveats about the next day reminder not working across browsers or devices, which may or may not be desirable.
As things stand while writing this (3rd Jan 2019):
There is no "desktop notification" that is not strictly "push notification" and works well cross platforms.
It is not possible to trigger a "desktop notification" without your app working in the background.
Service workers are not supposed to use timers and will be shut down.
The Operating System or other utility software may also suggest or even shut down your background application.
There is no client side only approach to trigger your notification at a precise time in the future. There are too many reasons for organisations not allowing this to happen at present.
Your only choice seems to be to use a different Push Notification Service coupled with an external scheduling service that would trigger the external notification based on custom schedules.
Your requirements as I understand them:
Each visitor would need to subscribe to push notifications
Record externally customer preference (for example: using some cloud scheduling)
Use the external scheduling service to trigger the push notification service.
PUSH NOTIFICATIONS are SERVER TRIGGERED not CLIENT REQUESTED
The main point of push notifications is that you should trigger the notification externally to avoid using resources on the end user device. This does not stop you collect notification preferences from users, save this information externally so you can trigger a notification externally when needed.
More information about PWA notification can be found in the following article:
https://developers.google.com/web/fundamentals/codelabs/push-notifications/
As far I know PWA Service Workers should not use timers!
As an alternative to using the PWA notifications, you may want to rightly consider using different notification service. For example FCM https://firebase.google.com/docs/cloud-messaging/
The idea could be to save externally the notification preference of the user and trigger the FCM notification via another cloud service when the scheduled time is reached.
Obviously those notifications will only ever work if the users are connected to the network. However this would have been also the case with any Notification service requiring network access.
I hope the above helps, Cheers and happy codding!
Assuming the notification data on your website will not be sent from the server. Using local storage will be the way to go.
You can store a variable to help track when to show the notification anytime the user hits your website:
localStorage.setItem("lastNotification", Date.now());
So you can have a script that does the following;
function notificationHelper(){
var lastTime = localStorage.getItem("lastNotification");
if(Date.now - lastTime > 86400000){
//Logic to show notication here
//set a new time at the end of the logic
}
//Otherwise Do Nothing
}
I am creating an Ionic 2 app with firebase and I need a way to listen to database changes (specifically on child_added) when the app is closed (I.e. in foreground,background and killed)
Basically, I want to use WebRTC to make calls within the app like whatsapp and I am following this post - https://websitebeaver.com/insanely-simple-webrtc-video-chat-using-firebase-with-codepen-demo
However, the only thing that puzzles me is how it will work when the app is closed. Can anyone please help me understand?
Thanks!
It's not possible to actively listen to database changes using the Firebase client SDK in exactly the same way that you can when your app's code is running.
If you want your app to receive information about changes to your database, you can instead use Firebase Cloud Messaging to send your app a notification with a small payload that contains information about the change. When your app receives the notification, it can then make a decision about what to do. There are some limitations with web support, so be sure to read about that.
Also look into Cloud Functions for Firebase to make it easier to write some server side code that can trigger in response to a database change and send a notification when those changes happen.
Hello I am developing an auction app like tophatter.com. I want to implement an application that has background process in it. I want this process to run forever until I stop it
http://eoction.com thatss our current site. The problem on our site when we refresh the page the auction also restart. We need something like a continuous process like tophatter.com if you refresh the page it will load the updated auction process.
I found this great service called pubnub. I am thinking we need a background process for this? This will process the auction on the pubnub blocks and then when we visit the site we will just need to query on its updated process?
Does pubnub support something like this?
PubNub Web Page Best Practices
When user refreshes your web app page or navigates to another page there are things you need to consider as a web app developer no matter what technologies you may be using. I will address, at a high level, the things you need to do when PubNub is integrated into your web page.
Restore Parameter
Whether the user interrupts your connection to PubNub or it is a network failure, you will want PubNub to reconnect and continue where it left off as much as possible. The PubNub JavaScript SDK has a initialization parameter called restore that when set to true, will reconnect to PubNub and get missed messages after the connection is dropped and reestablished.
var pubnub = new PubNub({
subscribeKey: "mySubscribeKey",
publishKey: "myPublishKey",
ssl: true,
uuid: getUUID();
restore: true
});
Reuse UUID
It is important to reuse the same UUID for each end user as this will allow PubNub to identify that user uniquely when it comes to Presence so that it doesn't produce new join events for the same end user. The PubNub JavaScript SDK actually generates a UUID and stores it in localStrorage and reuses it by default but very likely you have your own UUID that you would like to use for each of your end users.
Last Message Received Timetoken
If the network disruption is brief as is the case with a page refresh or page navigation, then missed messages are retrieved when restore:true is implemented in the init as stated above. But when the user is offline for more than say 5 minutes, you may want to retrieve missed messages on one or more channels. The best way to do this is to keep track of the timetoken of the last received message by storing it in localStorage every time a message is received via subscribe callback. When the user comes back online and it is has been more than 5 minutes since they were last online, call history using this last received message timetoken on each channel that you need to get missed message from.
Subscribe to Channels
Finally, you'll want to make sure that the user is subscribed to the channel they expect to be based on what their state prior to the connection disruption. If it is a page refresh, you likely just want to resubscribe them to the same list of channels. To do this, you just need to keep a list of channels they are currently subscribed to, once again, in localStorage. If the user navigates to a new page and this causes a full page reload (modern web apps should not require this, but...) then you may want to unsubscribe from some channel(s) and subscribe to new channel(s), it just depends on what that page navigation means to your app. Modern web app frameworks do not require full page reload for page navigation since the web app acts more like a desktop app than older web apps. And again, if the the user was offline for quite some time (more than 5 minutes) then it may not make sense to subscribe them to the same channels that they were subscribed to before. Really depends on your use case.
And by the way, Tophatter uses PubNub ;) but all of the above are generic best practice guidelines and recommendations and is not referencing any one app in particular.
EDIT: To address you question specifically, as pointed out in comments below...
You can't implement long-running process in PubNub BLOCKS (not currently, anyways), so you will need a server process for this. When the user refreshes the page, you just need to hit your server for current state. If using PubNub to keep this progress bar updated in realtime, you just subscribe to that channel that is sending the state of that progress bar and update your client. Using the same best practices I provided above are still necessary.
I want to know if it is possible to use javascript/html or php, etc... to create a page that receives continuous updates from a feed that uses PubSubHubbub?
How can I do this?
I am new to this, and any tips would be helpful.
Random suggestion - booth WebHooks and PubSubHubbub look cool. Article:
Webhooks let applications talk to each
other using very simple HTTP. Webhook
enabled applications run (so far) on
app hosting sites in the cloud. What
makes them different is that they
constantly scan for POSTS to a
designated URL. To use the
application, you register your
application with the other webhook
enabled application and provide a
callback URL. You POST data from
your app to the url of the receiving
app, and monitor the callback URL for
its response. Your app then takes the
POST it received and processes it.
Pubsubhubbub (PSHB) is a realtime,
multicasting webhooks enabled publish
and subscribe system. Historically on
the net, most information is received
after it is pulled. For example, we
set up receive intervals for our
email. Our browsers update our RSS
feeds at pre determined intervals. We
repeat the same searches over and
over, just looking to see if there is
anything new. Even when we get alerts
for new email or information, the
alerts are generated by actively
polling the source. PSHB changes that.