I'm using System.Runtime.Caching.MemoryCache to simulate a repeated task on a running .NET MVC application deployed on AppHarbor.
Entries in the cache are added using a CacheItemPolicy which contains an AbsoluteExpiration offset and a RemovedCallback that calls a method and retriggers the adding of the item in the cache (as described here)
MemoryCache is populated first time in Application_Start. It works fine locally, but doesn't seem to work once deployed on AppHarbor (tried also with HttpRuntime.Cache, same result).
My application is running under a CANOE (free) account on AppHarbor that only has one worker. Does this mean that I won't be able to simulate the background task until I upgrade to some paid plan?
Thanks!
Your application has to have visitors every once in a while for this to work. Other than StillAlive, Pingdom is also a good bet for generating requests to your app. You should also take a look at MomentApp. We expect to have background tasks ready shortly.
I don't think upgrading will help, they are working on adding background jobs to AppHarbor but to my knowledge they available yet.
What about using a service like https://stillalive.com/ to periodically hit a page on your site that then spins up a new thread and starts running your background task? Its available as a free add-on.
I was thinking of doing something like this while waiting for the background task functionality to be available.
Related
We are developing an app(iOS) in appcelerator which has a sync contact feature in it. This calls an API which syncs contacts with server. I want this to run in background of the app. It should not make the user stop on a screen. Can anyone help me on this?
If you use the iOS background it's only when the app goes to the background and has limitation set by the OS - so if, for example it takes too long to process, or if the OS needs memory - it will shut it down.
I'm guessing (correct me if I'm wrong) that you want to do the sync while the app is running, yet not compromise the user experience by freezing the app?
First of, know the the request to the server is made async - only processing the response is made on the js thread - so to make better use of your single thread I suggest you view the following presentation: http://www.slideshare.net/ronaldtreur/titanium-making-the-most-of-your-single-thread
If you truly want a background thread to do the job, currently you would have to write your own native module to do that.
Also, this is something to look forward to in future versions: https://github.com/appcelerator/cspec-titanium-multithreading
You can use the background service for that.
But be aware, that this services will stop after a few minutes
I have an ASP.WEB Web Api controller that needs to fire and forget some slow code. What would be a good way to do that? That is I want the controller to return an HTML response to the browser, while the slow code keeps running somewhere.
Is it a good idea to grab a worker thread from the tread pool and pass in a complex object created by the controller? Or do I need to write a separate windows service to do the work?
Your solution depends on the specifics or your situation and your workload.
You can certainly start of a new task Factory.StartNew when you receive a request.
There is nothing wrong with this technically.
Things you should think about though:
Do I have to return data back to the customer?
This task will use up web server resources so if those tasks take very long time and you get a lot of traffic you may run into situation where your customers are waiting in line to just start being processed. In this situation I think backend server with Windows Service be a much better idea.
All tasks above are subject to IIS Resets. They may be killed during processing your background task.
I have an application which contains a web application and a background worker.
I defined an AppHarbor.sln solution file, and included both projects. However, only the background worker gets deployed. Also, even the tests of the web application project seem to be ignored. I experimented with the project ordering in the solution file, but it's always the background worker that gets deployed.
Any ideas?
A free AppHarbor application only has a single worker associated by default. This can be either a background worker or a web worker (this is detected on the first successful build).
You probably just need to scale the number of web workers to 1 on the "Subscription" page, which will immediately trigger the deployment of the web application.
If the web application still isn't running you should check the build output to verify that it contains a web app.
AppHarbor has a FAQ which helps you troubleshoot problems like this. On your case I would recommend downloading the build output and verifying that everything is in order. Also feel free to contact AppHarbor support if you have any questions.
I observe the following weird behavior. I have an Azure web role which is deployed on love Azure cloud. Now I click "Configure" in the Azure Management Portal and change the number of instances - the portal shows some "activity". Now I open the browser and navigate to the URL assigned to my deployment and start refreshing the page something like once per two seconds. The page reloads fine many times and then fro some time it will stop reloading - the request will be rejected, then after something like half a minute the requests are handled normally.
What is happening? Is the web server temporarily stopped? How do I change number of instances so that HTTP requests to the role are handled at all times?
When you change the configuration file, your current instance might be restarted. This might be the reason you met with, which your website didn't response in about 30 seconds.
Please have a look http://msdn.microsoft.com/en-us/library/microsoft.windowsazure.serviceruntime.roleenvironment.changing.aspx and check if it 's because of the role restarting.
What you are doing is manual. Have you looked at the SDK for autoscaling Azure?
http://channel9.msdn.com/posts/Autoscaling-Windows-Azure-applications
Check out the demo at the 18 minute mark. It doesn't answer your question directly, but its a much more configurable/dynamic way of scaling Azure.
Azure updates your roles one update domain at a time, so in theory you should see no downtime when updating the config (provided you have at least two instances). However, if you refresh the browser every couple of seconds, it's possible that your requests go always to the same instance due to keep-alive.
It would be interesting to know what the behavior is if you disable keep-alives for your webrole. Note that this will have a performance impact, so you'll probably want to re-enable keep-alives after the exercise.
I created two very simple Heroku apps to test out the service, but it's often taking several seconds to load the page when I first visit them:
Cropify - Basic Sinatra App (on github)
Textile2HTML - Even more basic Sinatra App (on github)
All I did was create a simple Sinatra app and deploy it. I haven't done anything to mess with or test the Heroku servers. What can I do to improve response time? It's very slow right now and I'm not sure where to start. The code for the projects are on github if that helps.
If your application is unused for a while it gets unloaded (from the server memory).
On the first hit it gets loaded and stays loaded until some time passes without anyone accessing it.
This is done to save server resources. If no one uses your app why keep resources busy and not let someone who really needs use them ?
If your app has a lot of continous traffic it will never be unloaded.
There is an official note about this.
You might also want to investigate the caching options you have on Heroku w/ Varnish and Memcached. These are persisted independent of the dynos.
For example, if you have an unchanging homepage, you can cache that for extended periods in Varnish by adding Cache-Control headers to the response. Then your users won't experience the load hit until they want to "do something" rather than when they arrive.
You should check out Tom Robinson's answer to "Scalability: How Does Heroku Work?" on Quora: http://www.quora.com/Scalability/How-does-Heroku-work
Heroku divides up server resources among many different customers/applications. Your app is allotted blocks of computing power. Heroku partitions based on resource demand. When you have a popular application that demands more power, you can pay for more 'dynos' (application containers) and then get a larger chunk of the pie in return.
In your case though, you are running a free app that few people--if any outside of you--are visiting/using. Therefore, Heroku cuts down on the resources you're getting by unloading your app--putting it in hibernation essentially--until there is a request made to your address. When that happens, and your app has been idling for a long time, it takes time to reload.
Add 1 extra dyno to keep your app from falling asleep, if that reload time is important.
I am having the same problem. I deployed a Rails 3 (1.9.2) app last night and it's slow. I know that 1.9.2/Rails 3 is in BETA on Heroku but the support ticket said it should be fine using some instructions they sent me.
I understand that the first request after a long time takes the longest. Makes sense. But simply loading pages that don't even connect to a DB taking 10 seconds sometimes is pretty bad.
Anyway, you might want to try what I'm going to do. That is profile my app and see how long it takes locally. If it's taking 400ms then something is wrong. But if I get 50ms locally and it still takes 10 seconds on Heroku then something is definitely wrong.
Obviously, caching helps but you only get 5MB for free and once again, with ONE person using the site, it shouldn't be that slow.
I had the same problem with every app I have put on via heroku's free account. Now there are options of adding dynos so that your app does not get offloaded while it is not being used for a while, you can also try using redis or memcached for caching. But I used a hacky solution for my small scale project, I basically built web scraper put it inside an infinite loop with sleep and tada the website actually had much better response times(I guess it was not getting offloaded because of the script).