I need to run a long running task like report export, report import feature which will take few minutes to hour to complete the task. I want to start the task as soon as user gives command from the asp.net mvc view.
I found various web portals, but I couldn't find the exact solution I was looking for or might be I didn't got their idea (or, limited by my experience). I don't need something that runs at certain time interval or at certain time-stamp of the day/week. I only need the background job to be executed on user request and update the task as completed in DB after it's done. So, the background job need to be always triggered by user only.
I assume the ideal solution will be something like, Background service/job is always in ready state to accept trigger from my web application in some kind of port and as soon as it receives command from web application, it (a) either send everything to job when requested for action (b) or, just poke job to start its task (based on the updated db table entry made just before the call action) . So, the user can browse through other pages in the application and can view the progress of all such tasks in one of the view (where he can even cancel or see the completed task). Note, that there can be simultaneous request for the job from different web users which should be treated as separate job (As data export differs based on user access-rights).
I want to go with the simple method, with 100% assurance of task to be done/not done as recorded in db (no crashing of service). What are the best approaches (except azure jobs) as i want to implement the service within same server and I have access to the server/virtual machine to install windows services/packages if needed.
Take look at this great article that Hanselman wrote:
How to run Background Tasks in ASP.NET
Also Hangfire is a mature library that can make development of application long running process more easy.
Hangfire is an open-source framework that helps you to create, process and manage your background jobs, i.e. operations you don't want to put in your request processing pipeline
Related
Scenario
I have an web application which needs some calculations and processing on data. This job is a long running job(few hours). Job is initiated by user.
Requirement.
User Clicks on Process Data.
Some functions are called to start data processing.
Data Processing runs for hours.
User is given feedback of percentage completed etc.
Even if user logs off and then again log on he should get this feedback.
The requirement is somewhat similar to Spiceworks. Where it runs in background to detect the devices/computers in network and the user is notified in his page about the progress. But spicework uses windows service. We don't want to us windows service.
Now the question is.
What if user closes the page, will the task still run in background.
This task has to be completed fully.If terminated in between output will not have any meaning.
How to actually to design this long running process. In ASP.Net environment.
Also is there a way to show all/same user who logs in the status of processing.
There are multiple ways to schedule a job in the background. You can use SQL Job, Windows Service or Scheduled Tasks.
I would design it like this:
From my ASP.NET page - I will store an indication in the database for the job to start which will then be picked by the scheduled task. This task is nothing but a console application which pulls data from the database to see which tasks user initiated and then take the next action in there.. For the percetage complete you can store those values from your job into DB and your page will access the dB to show it to user anytime they come to the page.
Here is another thread where long running tasks in IIS are discussed:
Can I use threads to carry out long-running jobs on IIS?
The ASP.NET runtime is meant for short work loads that can be run in parallel. I need to be able to schedule periodic events and background tasks that may or may not run for much longer periods.
Given the above I have the following problems to deal with:
The AppDomain can shutdown due to changes (Web.config, bin, App_Code, etc.)
IIS recycles the AppPool on a regular basis (daily)
IIS itself might restart, or for that matter the server might crash
I'm not convinced that running this code inside ASP.NET is not the right thing to do, becuase it would allow for a simpler programming model. But doing so would require that an external service periodically makes requests to the app so that the application is keept running and that all background tasks are programmed with utter most care. They will have to be able to pause and resume thier work, in the event of an unexpected error.
My current line of thinking goes something like this:
If all jobs are registered in the database, it should be possible to use the database as a bookkeeping mechanism. In the case of an error, the database would contain all state necessary to resume the operation at the next opportunity given.
I'd really appriecate some feedback/advice, on this matter. I've been considering running a windows service and using some RPC solution as well, but it doesn't have the same appeal to me. And I'd instead have a lot of deployment issues and sycnhronizing tasks and code cross several applications. Due to my business needs this is less than optimial.
This is a shot in the dark since I don't know what database you use, but I'd recommend you to consider dialog timers and activation. Assuming that most of the jobs have to do some data manipulation, and is likely that all have to do only data manipulation, leveraging activation and timers give an extremely reliable job scheduling solution, entirely embedded in the database (no need for an external process/service, not dependencies outside the database bounds like msdb), and is a solution that ensures scheduled jobs can survive restarts, failover events and even disaster recovery restores. Simply put, once a job is scheduled it will run even if the database is restored one week later on a different machine.
Have a look at Asynchronous procedure execution for a related example.
And if this is too radical, at least have a look at Using Tables as Queues since storing the scheduled items in the database often falls under the 'pending queue' case.
I recommend that you have a look at Quartz.Net. It is open source and it will give you some ideas.
Using the database as a state-keeping mechanism is a completely valid idea. How complex it will be depends on how far you want to take it. In many cases you will ended up pairing your database logic with a Windows service to achieve the desired result.
FWIW, it is typically not a good practice to manually use the thread pool inside an ASP.Net application, though (contrary to what you may read) it actually works quite nicely other than the huge caveat that you can't guarantee it will work.
So if you needed a background thread that examined the state of some object every 30 seconds and you didn't care if it fired every 30 seconds or 29 seconds or 2 minutes (such as in a long app pool recycle), an ASP.Net-spawned thread is a quick and very dirty solution.
Asynchronously fired callbacks (such as on the ASP.Net Cache object) can also perform a sort of "behind the scenes" role.
I have faced similar challenges and ultimately opted for a Windows service that uses a combination of building blocks for maximum flexibility. Namely, I use:
1) WCF with implementation-specific types OR
2) Types that are meant to transport and manage objects that wrap a job OR
3) Completely generic, serializable objects contained in a custom wrapper. Since they are just a binary payload, this allows any object to be passed to the service. Once in the service, the wrapper defines what should happen to the object (e.g. invoke a method, gather a result, and optionally make that result available for return).
Ultimately, the web site is responsible for querying the service about its state. This querying can be as simple as polling or can use asynchronous callbacks with WCF (though I believe this also uses some sort of polling behind the scenes).
I tell you what I have do.
I have create a class called Atzenta that have a timer (1-2 second trigger).
I have also create a table on my temporary database that keep the jobs. The table knows the jobID, other parameters, priority, job status, messages.
I can add, or delete a job on this class. When there is no action to be done the timer is stop. When I add a job, then the timer starts again. (the timer is a thread by him self that can do parallel work). I use the System.Timers and not other timers for this.
The jobs can have different priority.
Now let say that I place a job on this table using the Atzenta class. The next time that the timer is trigger is check the query on this table and find the first available job and just run it. No other jobs run until this one is end.
Every synchronize and flags are done from the table. In the table I have flags for every job that show if its |wait to run|request to run|run|pause|finish|killed|
All jobs are all ready known functions or class (eg the creation of statistics).
For stop and start, I use the global.asax and the Application_Start, Application_End to start and pause the object that keep the tasks. For example when I do a job, and I get the Application_End ether I wait to finish and then stop the app, ether I stop the action, notify the table, and start again on application_start.
So I say, Atzenta.RunTheJob(Jobs.StatisticUpdate, ProductID); and then I add this job on table, open the timer, and then on trigger this job is run and I update the statistics for the given product id.
I use a table on a database to synchronize many pools that run the same web app and in fact its work that way. With a common table the synchronize of the jobs is easy and you avoid 2 pools to run the same job at the same time.
On my back office I have a simple table view to see the status of all jobs.
I would like to know the best way to deal with long running processes started on demand from an ASP.NET webpage.
The process may consist of various steps (like upload files to the server, run SSIS packages on them, execute some stored procedures etc.) and sometimes the process could take up to couple of hours to finish.
If I go for asynchronous execution using a WCF service, then what happens if the user closes the browser while the process is running, how the process success or failure result should be displayed to the user? To solve this, I choose one-way WCF service calls, but the problem with this is I need to create a process table and store the result (and error messages if it fails in any of the steps and which steps have completed successfully) in that table which is an additional overhead because there are many such processes with various steps that the user can invoke from the web page and user needs to be made aware of the progress (in simplest case, the status can be "process xyz running") and once it is done, the output needs to be displayed to the user (for example by running a stored procedure).
What is the best way to design the solution for this?
As I see it, you have three options
Have a long running page where the user waits for the response. If this is several hours, you're going to have many usability problems, so I wouldn't even consider it.
Create a process table to store the results of operations. Run service functions asynchronously and delegate logging the results to the service. There can be a page that the user refreshes which gets the latest results of this table.
If you really don't want to create a table, then store all the current process details in the users' session state, and have a current processes page as above. You have the possible issue that the session might timeout, or the web app might restart and you'll lose all this.
I can't see that number 2 is such a great hardship. You could make the table fairly generic to encompass all types of processes: process details could just be encoded as binary or xml and interpreted by the web application. You then have the most robust solution.
I cant say what the best way would be but using Windows Workflow Foundation for such long running processes is definitely one way to go about it.
You can do tracking of the process to see what stage it is at, even persist it if you have steps where it is awaiting user input etc.
WF provides a lot of features out of the box (especially if your storage medium is SQL Server) and may be a good option to consider.
http://www.codeproject.com/KB/WF/WF4Extensions.aspx might help give you some more insight into the same.
I think you are in the right track. You should run the process asynchronously, store the execution somewhere (a table), and keep status of the running process in there.
Your user should see a pending display label while the process is executing, and a finished label with the result when the process finished. If the user closed the browser, she will see the result of her running process next time she logs in.
What are your most successful ways of running a long process, like 2 hours, in asp.net and return information to the client on the progress.
I've heard creating a windows service, httphandler and remoting can be successful.
Just a suggestion...
If you have logic that you are tyring to utilize already in asp.net... You could make an external app (windows service, console app, etc.) that calls a web service on your asp.net page.
For example, I had a similiar problem where the code I needed was asp.net and I needed to update about 3000 clients using this code. It started timing out, so I exposed the code through a web service. Then, instead of trying to run the whole 3000 clients at through asp.net all at once, I used a console app that is run by a nightly sql server job that ran the web service once for each client. This way all the time consuming processing was handled by the console app that doesn't have the time out issue, but the code we had already wrote in asp.net did not have to be recreated. In the end slighty modifying the design of my existing architecture allowed me easily get around this problem.
It really depends on the environment and constraints you have to deal with...Hope this helps.
There are two ways that I have handled this. First, you can simply run the process and let the client time out. This has two drawbacks: the UI isn't in synch and you are tying up an IIS thread for non-html purposes (I did this for a process that used to return quickly enough but that grew beyond time-out limits).
The better way to handle this is to write a "Service" application that handles the request as passed through a database table (put the details of the request there). Then you can create a window that gives the user a "window" into ongoing progress on the task (e.g. how many records have been processed or emails sent). This status window can either have a link to permit the user to refresh or you can automate the refresh using Ajax callbacks on a timer.
This isn't directly applicable but I wrote code that will let you run processes similar to "scheduled tasks" inside of ASP.NET without needing to use windows services or any type of cron jobs.
Scheduled Tasks in ASP.NET!
I very much prefer WCF service to scheduled tasks. You might (off the top of my head) pass an addr to the WCF service as a sort of 'callback' that the service can call with progress reports as it works.
I'd shy away from scheduled tasks... too course grained.
We have an ASP.Net application that provides administrators to work with and perform operations on large sets of records. For example, we have a "Polish Data" task that an administrator can perform to clean up data for a record (e.g. reformat phone numbers, social security numbers, etc.) When performed on a small number of records, the task completes relatively quickly. However, when a user performs the task on a larger set of records, the task may take several minutes or longer to complete. So, we want to implement these kinds of tasks using some kind of asynchronous pattern. For example, we want to be able to launch the task, and then use AJAX polling to provide a progress bar and status information.
I have been looking into using the BackgroundWorker class, but I have read some things online that make me pause. I would love to get some additional advice on this.
For example, I understand that the BackgroundWorker will actually use the thread pool from the current application. In my case, the application is an ASP.Net web site. I have read that this can be a problem because when the application recycles, the background workers will be terminated. Some of the jobs I mentioned above may take 3 minutes, but others may take a few hours.
Also, we may have several hundred administrators all performing similar operations during the day. Will the ASP.Net application thread pool be able to handle all of these background jobs efficiently while still performing it's normal request processing?
So, I am trying to determine if using the BackgroundWorker class and approach is right for our needs. Should I be looking at an alternative approach?
Thanks and sorry for such a long post!
Kevin
In your case it actually sounds like the solution you will be looking for is multifaceted (and not a simple in and done project).
Since you said that some processes can last for hours that is absolutely not something for ASP.NET to own. This should be ran inside a windows service and managed with native windows threading.
You will need to implement some type of work queue in your service and a way to communicate with the queue. One way is to expose a WCF service for all actions your service will govern. Another would be to have service poll a database table and pick up work from the table.
To be able express the status of the process you will want the ASP.NET application to be able to have some reference to the processID for example the WCF service returns a guid identifier. Then you have a method that when you give it the processID it will return the status of the process. You can then implement the polling of that service call using AJAX and display any type of modal you wish.
Another thing to remember is that you need to design your processes to have knowledge of where it is and where it will be when it is finished so it can track the state it's in. For example, BatchJobA is run and will have 1000 records to process. The service needs to know what record it's on or what the current % of competition is for it to be able to return information to the UI. For sql queries that take a very long time to execute this can be very problematic to accurately gauge where it is unless you do alot of pre and post processing of temp tables that you can in the middle of it read the status of the temp tables to understand where it is.
Based on what you are saying I think that BackgroundWorker is not a good choice.
Furthermore keeping this functionality as a part of your main app can be problematic, specifically because you do not want the submitted processing to be interrupted if the main app recycles. You can play with asynch processing but it still will be a part of the main app AppDomain - all of it will die if the app recycles.
I would suggest buidling a separate app implementing this functionality. In a similar situation I separated background processing to a Windows service and hosted a web service in it as a means of communication
You might consider a slightly different approach.
For example, have a command and control table in which you send commands like "REFORMAT PHONE NUMBERS" or whatever.
Then have a windows service monitoring that table. Whenever a record shows up, run the command.
This eliminates any sort of worry about a background thread. Further you have a bit more flexibility with regards to what's in the queue, order of operations including priority, etc. Finally, you would have a definitive list of what is running or needs to run.
As an option, instead of a windows service you might just use a SQL job to execute every so often to watch your control table and perform the requested action.