For example Zendesk has a feature called Agent Collision Notification - when you edit a ticket you get a note if somebody else its editing this ticket.
What is the Infrastructure to support a feature like this? This question seems to aim at the same thing but at a much lower level.
For the system to be completely dynamic (also notifying the first viewer) and reasonable fast, probably some comet or websocket like stuff is needed. But unlike in chat systems (a prime comet example) in a Ticket system users are constantly switching pages.
What would be the program flow and the server infrastructure for a thing like this?
If you want to allow realtime collaboration then this question that also mentions Operational Transforms will be of interest to you. And there's also a question about operational transformation libraries.
What would be the program flow and the server infrastructure for a thing like this?
I work for Pusher so I can tell you one solution using our technology.
User A opens page where there could be a 'collision'. Within the page subscribe to a channel for the page.
User A starts editing the page. Send an AJAX request to the server so there is some persisted state about the fact the page is being edited. Trigger an event on the channel stating that the user is editing the page.
User B opens the page. The page loads and can display the information from the persisted state that the page is being edited.
User A finishes editing and a request is made to the server to update the page state. Trigger an event indicating that nobody is editing the page. This event will be distributed to User B (the updated page can also be distributed via within the event or via an AJAX request when the event is received).
User B now knows he/she can edit the page. They begin editing (see step 2.) and User A is notified that User B is now editing the page.
It would also be quite cool to use presence so you could see who else was viewing the page and to allow the users to discuss changes as they happen.
Related
So I have an application that allows users to invite each other to different events. Previously I had a separate collection called Invites that contained an entry for each user and an array of events they were invited to. Since I'm building a prototype, I have insecure on, and I would simply update Invites from the client side.
Recently I changed this so that when a user invites another to an event, it calls a meteor method and updates both the inviter and the invitee's profiles on the client side.
Now my app is running very slowly and I'm not sure why. Even just loading the first page of the app (the login button for example, which uses accounts UI takes forever to load). Since the changes to invitations are the only changes I've made, I'm guessing this is the issue. Is storing invitations on each user's profile the wrong way to go about this? Any ideas about how to debug this slowness? I'm new to meteor/ web dev in general and I'm not sure what the best practices are for writing efficient code.
I would like to ask, if it is a good idea to use SinglR just for knowing if the current user now online or not?
For example I have an small website with log in system, and some where on the side i would like to show the logged in members.
Is this a good idea to use signalr for that?
And if it the case should I then on each page start the connection with hub? (In this case when user navigates on the pages, will be the ReConnected method called on hub, or OnDisconnected and OnConnected)?
I'm just starting with signalr, so curious what ppl think.
You could use SignalR though there might be better methods to do this. So when a user logs in, logs out or becomes inactive - you would have some sort of message being sent from the client to the server that indicates the change in status. You can store that information in a temporary database and whenever a value in the database changes you can use SignalR to relay that information to all the connected clients.
Signalr will get reconnected when the user moves from one page to another page. Whenever a user logs into a website the user security details will be persisted in a cookie assuming you are using Cookiebase authentication. So till the user logs out or session timesout the cookie will be active. So there is no real need for Signalr here.
I have been investigating the same thing. From my research, I would say that you COULD do this, but I'm on the fence of whether it's the best way to go about it. I would expect a LOT of disconnecting, connecting and reconnecting. If you're persisting this data in a database, you should anticipate a lot of database traffic. if you're only on a single server though, you could just persist this in memory.
Something to also note is that the ConnectionId changes with each page refresh. At first, I thought that was dumb because I wanted the connection id to be consistent so i could keep a handle on a user with it. However, if you open a link in a new tab and then close one of them, you have to still keep the other connection in storage. If the id was the same you would remove it on disconnect even though the other tab was open, so your user would incorrectly be marked as offline.
However, the other issue that i'm thinking about is that if you're just browsing around the site in a single tab, you will disconnect for a split second between each page load. So you might run into connection consistency issues with that.
I'd say online presence with signalr is more common to be used for a chat room or game lobby. So I'd say this is possible, but whether it's a good solution -- i'm unsure.
I am developing a matrimonial web application in asp.net. In that I want to display number of users in online (logged in).
I am planning to maintain a "login-status table" in dB. And will maintain the table every time the user have logged in and out. But there is problem if the user have closed the browser directly without logging out.
Is there any other easy way to achieve this. Pleas provide sample code.
And I want to know how can I update the table that if the user click the browser's close button.
I recently implemented something similar. The challenge I had is what defines "online". What if the user walks away from the computer, closes the browser, network is disconnected?
In the end I went with online means visited a page in the last 15 minutes. It avoids the issues with trying to detect when they walk away from the browser, or close it.
I did consider binding to the browsers onclose event and hitting a /user/closed/browser url. I have used that before in a call center website to unlock the call. But really the 15 minute rule was "good enough".
I coded it by keeping an in memory dictionary that I persisted to db every 5 minutes. Sorry I have no code to provide.
How to restrict the page by accessing only one user at a time. Using asp.net can i use global.asax, is there any other way to restrict, if one user accessing the page, another user not able to access that page. we have to give message that one user is accessing the page. is it possible. can you help me or give some reference.
Although there are probably many better ways of dealing with this sort of problem, I'm going to assume that you do actually need this.
What I would do:
Make your application so that when the page is loaded(when it isn't "locked"), it logs to a database that the page was loaded and "lock" it. In the actual page, I'd have some kind of AJAX to constantly poll the web server every 5-15 seconds to tell your application the user is still on the page. And then make it so that the page becomes unlocked after 5-15 seconds from the time saved to the database by the last AJAX call.
Again, I really suspect that there is a better way around an issue like this, but this is a direct answer to your question
Based on this:
yeah sure, jupaol, it is depend on accounts, in my web application, one report has to approve only one user, but the approve authority having two users. if both of them accessing the same page and approve at a time, it will big mess. here i an not using database.
The problem is related with concurrency, there are several ways to face an issue like this, for example the easiest one is to use optimistic concurrency. Even when you are not using a database for this, you can emulate it.
You should be storing the result of the approvers somewhere, in order to mark the report as approved, with this in mind you should be able to do something like this:
Before render the page get the latest report status
If the report has not been approved, render normally
If the report was approved seconds before, render it in read-only mode reporting who approved it (or similar approach)
Add a validation to your ChangeStatus method, in this method do the following:
Get the latest status of the current report
If the report is still not validated, then block the thread (you could use a Mutex or similar) and mark the report as validate it
If the report was already validate it, raise a domain exception and handle it in your page correctly (perhaps render the page in read-only mode explaining that the report was already validate it)
If you want a more responsive application, (RIA), you might want to consider the following approaches:
Perhaps this would be the worst approach but it's still an option, you could keep a log tracking when a user request your page, then in subsequent requests check if the log is still valid, if it is not, then redirect to another page indicating the page is in use, otherwise allow access to the page. I believe this is an error-prone approach because you would be relying on this simple validation in order to prevent an inconsistency in your system, besides you would have the polling problem described in the following approach
Using AJAX to poll data from a service checking if the report has been approved. Perhaps this is the easiest way to accomplish this but it is not recommended it, because you would be polling your server constantly, and eventually you would have scalability problems
You could use Comet to get notified to the browser (client) whenever a server event has occurred, in this case when your report has been approved. The problem with this approach is that you have to keep an opened connection with the server in order to get notified.
The last approach and the most recommended these days is to use Web Sockets, this is the technology used in StackOverflow to get notifications in real time.
How do I disable offline caching for firefox in ASP.NET or in IIS? I found this post:
Disabling browser caching for all browsers from ASP.NET
This doesn't address the issue completely. It just disables caching from the back button (when not in off-line mode).
Here is a simple scenario:
If user A logs on to his bank. User A is doing transactions and he even goes to update some personal data. Finally user A is done and logs off from his bank website. User A leaves the browser on, because he has another tab open downloading a file that is a few gigs. User B would like to go on to his email to send out some emails, so user A doesn't close the browser. He knows the security risks, because he has read what must be done once you log off of the site, but he doesn't want to stop the download. For user A, to have to redownload is too much time for him and well he is just your typical user and doesn't think user B (being a good friend of his) will do anything malicious. So then user B uses the browser. The first thing user B does is "work offline". User B now has all data from user A. The page has an off-line cache for user B to see. User B is now able to open the history to view those cached pages, or just simply click back if the page was left open (either way works). User B now has all the pages that user A has browsed to. So any sensitive data is now his.
Does anyone know if this is possible to control at the server level. I know in firefox you go to about:config, but that is not an option for the server to tweak. Even so this can be told to the user, but not every user is going to be able to do this (being too complicated for some users) or some users will just ignore the warnings out of laziness or just not reading what the page says. I know there will be that one person that will say, "oh well that's their own fault and they deserve that". I honestly think ignorance in this sense is not the user's fault. Consider an older person in their 80s who is not technology-centric (like my father who I constantly give him the do's and don't's about online, but he still doesn't really understand the risks completely).
So I reiterate again, is it possible to disable this kind of off-line caching at the server level? I also found this post:
http://forums.asp.net/post/1386380.aspx
Would this help at all? Any help please. Please be constructive and not start a debate. I think I have been very clear, and I have done a lot of research on this with no luck. Please note that only the off-line caching on firefox is what is giving the problem, on every other browser (or on firefox onlinle) the caching has been disabled as expected.
Update:
I actually already have what the last link suggests (http://forums.asp.net/post/1386380.aspx) and it still doesn't prevent the problem.
Disabling cache from server side is kind of impossible because server can only request the browser to not store in cache. Rest is up to the browser to follow it or not.
The best option is not to send the data to browser , so it is never cached, instead fetch it on demand using json/Xml or any thing you are comfortable with.
The only trick that worked for me was to remove all sensitive information from loading via regular page methods, and load it via ajax/jquery on window.ready event. Once I implemented callback and ajax the back button and 'work offline' problem got solved but rolling out that with ajax callback was really a big task.