I have been using PushSharp during these last 4 years without too much trouble, and I lately experience problems when sending to more than one device at a time. I was wondering if in a Web environment there is a need to run the PushSharp process in a separate thread in the background or if PushSharp will do that anyway. The reason is that if a web page triggers the push, it will kill the thread as soon as it finishes (although framework 4.5.2 introduced QueueBackgroundWorkItem that will continue to run, but I could not see any difference). On the second hand if the PushSharp task takes too long it will keep the web page busy for an unnecessary time that may be long if there a lot of notifications to send.
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Maybe it's a simple question, but I don't get it. When should I use concureency in my javafx project? Is it right that I should use for every task, which do some action in the background, the Concurrency API? So every action in my controller class, which has nothing to do with the UI should be executed in a single task?
I really don't get it how to use this right....
Whenever you have a task that may take sometime to get executed or there is a possibility of delayed response, you do not want your JavaFX Application thread to wait for it, because, as long as the JavaFX Application thread waits for the response, the UI becomes unresponsive.
A few examples where you may want to use a background thread is :
An I/O operation
A web service call
From the JavaFX documentation :
Implementing long-running tasks on the JavaFX Application thread inevitably makes an application UI unresponsive.
On the other hand, if you have minor calculations or some task which can be completed in a jiffy (I am not sure if this is the correct word, but I hope you can relate to what I want to say) and will not put the JavaFX Application thread on wait, you can execute them on the same thread.
I am working on windows azure cloud service. First time when i click on login button it takes 6 to 7 seconds but after sometime when i click on same login button it takes 2 seconds. I am not able to understand why it is happening so though the server side code is same for both processing but subsequent calls are quiet faster than first call ?.
"First-hit" delay is very common with ASP.NET applications. There is the overhead of JIT compilation, and various "pools" (database connections, threads, etc) may not be initialized. If you have an ASP.NET Web Forms application, each .aspx page is compiled the first time it is accessed, not when the server starts up. Also the various caching mechanisms (server or client) that make subsequent requests faster are not initialized on that first hit. And on the very first hit, any code in Application_Start will be run, setting up routing tables and doing any other initialization.
There are various things you can do to prevent your users from seeing this delay. The simplest is to write some kind of automated process that hits every page and run it after deploying a new release. There are also modules for IIS that will run code ahead of the Application_Start, when the site is actually deployed. Search for "ASP.NET warmup" to find those.
You may also experience delays after a period of inactivity, if your ASP.NET App Pool is recycled - this resets a bunch of things and causes start-up code to be run again on the next request. You can ameliorate this effect by setting up something to ping a page on your site frequently so that if the app pool is recycled it is warmed up again automatically, instead of on the next actual user request. Using an uptime monitoring service will work for this, or a Scheduled Task within the Azure ecosystem itself.
Technology used: EJB 3.1, Java EE 6, GlassFish 3.1.
I need to implement a background job that is execute every 2 minutes to check the status of a list of servers. I already implemented a timer and my function updateStatus get called every two minutes.
The problem is I want to use a thread to do the update because in case the timer is triggered again but my function called is not done, i will like to kill the thread and start a new one.
I understand I cannot use thread with EJB 3.1 so how should I do that? I don't really want to introduce JMS either.
You should simply use and EJB Timer for this.
When the job finishes, simply have the job reschedule itself. If you don't want the job to take more that some amount of time, then monitor the system time in the process, and when it goes to long, stop the job and reschedule it.
The other thing you need to manage is the fact that if the job is running when the server goes down, it will restart automatically when the server comes back up. You would be wise to have a startup process that scans the current jobs that exist in the Timer system, and if yours is not there, then you need to submit a new one. After that the job should take care of itself until your deploy (which erases existing Timer jobs).
The only other issue is that if the job is dependent upon some initialization code that runs on server startup, it is quite possible that the job will start BEFORE this happens when the server is firing up. So, may need to have to manage that start up race condition (or simply ensure that the job "Fails fast", and resubmits itself).
I have a site which sometimes takes particularly long to process a request (and that's not a defect). 99% of the time it's pretty quick because it almost doesn't do any processing.
I want to show a message that says "Loading" when the site takes long to process the request. My site uses mod_wsgi and Apache. The way I see it, I would respond saying 'Loading' before completing the processing and do one of two things right before:
-spawn a (daemon) thread to take care of the processing.
-communicate through socket with other process and tell it to take care of the processing (most likely send request to http://localhost:8080/do_processing).
What are the pros and cons of one approach vs the other?
Using a separate process is better. It does not have to be hard at all as suggested in another answer as you can use an existing system for doing exactly that such as Celery (http://celeryproject.org/). Relying on in process threads is not necessarily a good idea unless you are going to implement an internal job queueing system of your own to prevent blowing out of number of threads. Also, in a multiprocess server configuration you cant be guaranteed a request comes back to the same process and so not easy to get status of a running operation. Finally, the web server processes could get killed off and thus your background task could also be killed before it finishes. You would need to have a mechanism for holding state which can survive such an event if that was important. Far easier to use something like Celery.
The process route requires quite a bit of a system processing. Creation of a separate process is relatively expensive and slow. However if your process crashes it doesn't affect your main governing process (you will receive the exit status code and will have an opportunity to respawn a new working process). You will also need some sort of InterProcessCommunication layer (can be a socket, pipe, shared memory, etc...) which is adds to complexity if your project.
Threads are lightweight and cheap. All you need to do is to manage concurrent access to shared resources. So it really depends on the task you have in mind. Threads probably will be more likely the appropriate way to implement your task.
We are having a web application build using asp.net 3.5 & SQL server as database which is quite big and used by around 300 super users for managing around 5000 staffs.
Now we are implementing SMS functionality into the application which means the users will be able to send and receive SMS. Every two minute the SMS server of the third party is pinged to check whether there are any new messages. Also SMS are hold in queue and send every time interval of 15 to 30 minutes.
I want this checking and sending process to run in the background of the application all the time, even if the user closes the browser window.
I need some advice on how do I do this?
Will using thread will achieve this or do I need to create a windows service for it or are there any other options?
More information:
I want to execute a task in a timer, what will happen if I close the browser window, the task wont be completed isn't it so.
For example I am saving 10 records to the database in a time interval of 5 minutes, which means every 5 minutes when the timer tick event fires, a record is inserted into the database.
How do I run this task if I close the browser window?
I tried looking at windows service but how do I pass a generic collection of data to it for processing.
There really is no thread or service choice, a service can (and usually is!) multi threaded, a thread can start a service.
There are three basic choices you can:-
Somehow start another thread running when a user logs in -- this is probably a very poor choice for what you want, as you cannot really keep it running once the user session is lost.
Write a fully fledged windows service which is starts on OS startup and continues running unitl the server is shutdown. You can make this dependant on the SQLserver service, so it starts after the DB is available. This is the "best" solution but may be overkill for your purposes. Aslo you need to know the services API to write it properly as you need to respond correctly to shutdown and status requests.
You can schedule your task periodically using either the Windows schedular, or, preferably the schedular which is built in to SQLServer, I think this would be the most suitable option for your needs.
Distinguish between what the browser is doing and what's happening server-side.
Your Web App is sitting server-side waiting for requests from whatever browsers may be running, and servicing those requests, in servicing those requests I guess it may well put messages on a queue and have a look in a database for any new messages.
You want the daemon processor, which talks to the third-party SMS, to be triggered by time rather than by browser function. Either of your suggestions would work:
A competely independent service could run and work against the queues and database.
Your web app, which I assume is already a service, could spawn a thread
In either case we have a few technical questions of avoiding any race conditions between the browser-request processing and the daemon - but databases and queueing systems can deal with that.
So I would decide between stand-alone daemon and background thread like this:
Which is easier to implement? I'm a Java EE developer, I know in my app server I have an API for specifying code to be run according to a timer, the API deals with the threading issues. So for me that's very easy. I don't know what you have available. Timers are not quite as trivial as they may appear - so having a reliable API is beneficial. If this was a more complex requirement, where the daemon code were gnarly and might possibly interfere with the WebApp code then I might prefer to keep it conspicuously separate.
Which is easier to deploy and administer? Deploy separate Web App and daemon, or deploy one thing. In the Java EE world we could have a single Enterprise Application with all the code, so that's a single thing to deploy, start and control.
One other thing to consider: Scaling and Resilience. You might choose to have more than one copy of your web app running, either to provide fail-over capabilities or just because you need the extra power. In which case how many daemons would you have? Would it be a problem to have two daemons running? You might need some extra code to mediate between two daemons, for example log in the database the time of last work, each daemon can say "Oh, my buddy balready did the 10:30 job, I'll go back to sleep"