I've got two applications: Interface is a Rails app and Processor is for bash scripts.
I need to notify an Interface user's session if a bash process on Processor fails. I have access to the command line on Processor, so I can hit http://interface.com/process/12/error/:error_message with :error_message set on Processor.
I'm not sure how to make that work though. That route works from the browser, but I don't know how to redirect the user with the error message.
Any help would be great.
Thanks.
To answer this, I am going to make some assumptions about your setup. Please correct me if I don't have it right.
I assume that your Interface user is monitoring your site by visiting a page such as http://interface.com/process/12/monitor on the Interface server and you want the error message to pop up to let them know something went wrong.
Given that, consider having your call to http://interface.com/process/12/error/:error_message store the error in a related ProcessError table. Then, use javascript on the monitor page to poll the Interface server for "new" errors. The polling interval really depends on the situation. If you're the only user, every second would be fine, but if there are going to be lots of monitoring users at once, you would probably want to make the polling interval longer. How long depends on load and how important it is that the user is notified quickly.
A push solution would be more efficient, but is a bit harder to accomplish. If this is appealing to you, have a look at Faye, a publish-subscribe messaging system that supports Rails servers and html+javascript clients.
Hopefully this points you in the right direction!
Related
So this is something I've been racking my brain about a bit, consider the following scenario:
I'm working on my project, I build it, and in my bundle is a lazyloaded module: module-a-[oldhash].js, that will get lazyloaded at some point in time.
Everything is fine and dandy.
I do some more work on my project, create a new bundle, deploy, and now my content hash has changed: module-a-[newhash].js. I deploy, go to my page, my service worker calls skipWaiting, but my page still tries to request module-a-[oldhash].js, which now no longer exists.
How do I go about this? The only way that I can think of handling this, is show an 'update available' message that posts a skipWaiting message to the service worker, and reloads the page on controllerchange event. But I'm curious if theres no way to achieve to same thing without having to include such a notification/toast pattern and a reload.
Additionally, its my understanding that this would only pose a problem with lazyloaded resources
Is my understanding of these problems correct? What are some common patterns for dealing with this?
Pretty much everything you describe there is correct. I'll just point out that this is a problem that extends beyond the use of a service worker. It can easily happen with long-lived single page apps that attempt to lazy-load a URL that has been replaced server-side with a new deployment.
There's some general information about the problem and potential solutions collected on at this Paying Attention while Loading Lazily site and associated video.
In general, the best practice is to:
Always assume that lazy-loading might fail (for whatever reason) and handle those failures gracefully. One approach might be to ask a user to reload the page upon encountering a failure.
Using a cache-first service worker can help protect against lazy-loading failures, at the expense of delaying updates until the newly installed service worker moves from waiting to active. As you mentioned, the best practice tends to be to show something in your UI letting a user know that updates are available, and once they opt-in to accepting those updates, postMessage() to the service worker telling it to call skipWaiting(). And finally, listening for the controllerchange event and calling window.location.reload() when that's fired.
I have a requirement to inform every user to save their work and logout so that admin can reset iis or do some changes in the asp.net MVC application server.
looping through session object collection is not thread safe that is what i have learned.
any other ideas?
and even if i can get hold of active sessions how do i send a message to those clients ?
thanks in advance.
Save the message in a database and query the database for every request to see if a message exist.
This seems like a poorly-defined requirement.
Serious maintenance should be done at a specific time, and users should be alerted to that time window well in advance.
Simply restarting IIS is a pretty quick procedure... is there any reason users would lose their work when simply restarting IIS? While I've been filling out this StackOverflow answer, for instance, they could have restarted the server a dozen times. Once I hit Post, if the server is down, it'll either timeout and leave my work in the textarea, or else it will connect successfully if the server is back in time.
If I'm not submitting data, but just clicking a link, the same applies: either the browser times out, in which case a simple refresh is enough once the server is back up, or it eventually takes the user where they want to go.
If you're doing pure AJAX requests you will need to handle a missing server yourself, rather than relying on the browser to do it, but you'd need to work that out anyway because of the Eight Fallacies of Distributed Computing #1: "The network is reliable." (see http://en.wikipedia.org/wiki/Fallacies_of_Distributed_Computing)
So, I'd actually push back on that requirement. They're asking you to do something that won't really meet the need (users don't lose data, have a reasonably good experience), that will become complicated, and that will be a brittle solution in the end.
Sounds like a case for SignalR!
https://github.com/SignalR/SignalR
So after two days of googling incessantly and apparently asking the wrong questions, I think I have figured out a way to word it so I get the response I'm looking for.
I have a Project Management application, written in MVC3. Sometimes, the users have to attach large files and upload them to the applications. (100-200 mb) is typical. The problem of course is that this is currently handled synchronously, and varying network speeds mean that the application can be completely blocked for 10 minutes to an hour if someone's on a slow connection. FTP is NOT an option here (my hands are tied by our network guys on that one).
So I am looking for a way to do the following workflow:
user clicks Upload File
user selects File to upload
user clicks "Go" or whatever button
Application says "your file is being uploaded. You will be notified when it's complete"
user continues to use the application as normal.
Some things to be aware of: I already have an internal messaging system implemented. So when I say that the app will notify the user when it's complete - all it needs to do is insert a new message into the queue. It DOES NOT need to notify the user's current screen or anything like that - so I'm not worried about a return value of any kind. I also have a background Error log implemented, so I can insert a message into the log if something goes wrong and again - inform the user via the internal messaging system.
So I am stumped on how to implement this. I thought an Async Controller was the right way to go, but if I understand all the stuff I've been seeing - it's not. Feel free to correct me. I implemented a version using Async but when addressing the one problem it had, I was informed that I was doing it wrong anyway.
So uh...help? I'm all ears.
If you can use 3rd party controls then take a look at the Telerik controls:
http://www.telerik.com/products/aspnet-mvc/upload.aspx
It has an Asynchronous File Upload control.
I would like to make an emailing in my symfony project.
The user admin log-in in the backend and click on the button "start emailing", then 8000 emails is sending (2 per second). The admin user can close his page and go back a few moment later to see the emailing's progression. (10%...., then 20%... etc).
How can i do ? I think a have to use CRON TASK, but i'm not sure...
Maybe there is a better/other solution ?
Can you explain me the best way to program my emailing ?
Thanks, and sorry for my english!
The best way to rate the sending would be setting your MTA to do that for you. If it's a application requirement then go for Gearman. There is this awesome wrapper for the PHP interface (http://www.symfony-project.org/plugins/sfGearmanPlugin). It works really well.
Cron tasks do not know if the previous running instance has finished the job. It really messes thing easily up. For those cases, like yours, that you need to back processing, the best choice is a solution like Gearman.
We are looking at setting up an internal web application (ASP.NET MVC) as a kiosk for the employees that don't have a dedicated computer. We currently do not have this kiosk setup. Each employee will have their own login to look at some basic payroll information and request leaves of absence. This same web application will be used by the office workers with a dedicated PC at their desk.
I am going to go out on a limb and say that no matter how many times we tell the employees, the employees will not click log off when they walk away from the kiosk. What would you do to help prevent this from happening?
lets try to fix the users instead of the code :) , i guess that your log out button is like the one here on stackoverflow. its a little text link "logout" some where in the upper right corner. thats perfect for people who use webapps day by day and are aware of the fact that they need to logout before someone comes along a does havoc to thier facebook profile, but less tech savy users wont think of that and walk away.
you need to the get the attention of your users to this logout-button and teach them that logging-out is a good thing.
try the following
give the logout button more visual weight then usally make it bigger, make it a real button instead of a textlink and even change its color to something more alerting (red, orange, ... whatever fits your ci)
if they dont loggout, use the session timeout and some javascript the refresh the page after any amount of inactivity, but also set a flag that this user has not logged out after his last visit. that way you can greet him on his next login with a nice confirmation dialog, and tell him once again why logging out is so important and where your logout-button is located.
The naive solution would be to enforce a timeout. If there's no activity from the user within a certain time limit (say, a minute or so), log them out. Of course, this won't prevent someone from walking up immediately after an employee is done and seeing how much money they make.
ATMs handle this, I think, by timing out after a minute or two, which isn't super-secure but at least offers some minimal security.
If the employees have any kind of RFID card or other security token, you could require them to put it in a reader slot, and log them out whenever the card disappears. Handling this within a web app, though, could get complicated.
The simple way is to use a little javascript.
Just have it set to something like 30 seconds of inactivity. If the user hasn't clicked on anything have the javascript send it back to a login page.
Here's a link to get you started.
Assuming you've already thought of the obvious (aggressive session timeouts, non-persistent authentication cookies, etc); how about a bit of an "out there" suggestion?
I'm not sure how do-able this would be with a web-based interface; but what about using some form of IR sensor with a usb/serial interface and an API you can tie into? This may make it possible to invoke some form of "logout" operation when someone walks away from the kiosk.
Perhaps someone has a better suggestion for external hardware, but this was the first thing that lept to my mind as a out-of-the-box approach.
I found a jQuery version that seems to work quite well. I'll start by using that and see how that goes.