Let me give a back ground for everybody before I go to my problem. My company hosts website for many clients, my company also contracts some of the work to another company.
So when we first set up a website with all the informations to our clients, we pass that information to the other company we contracted and three of us have the same data. Problem is once the site is up and running, our clients will change some data and when ever they do that we should be able to update our contracted company.
The way we transfer data to the contracted company is by using a web service (httppost, xml data). Now my question is what it the best way to write a program which sends updated data to the contracted company everytime our clients change some data.
1) Write a windows service having a timer inside my code where every 30min or so connects to the database and find all changes and send it to the contracted company
2) Write the same code as #1 (with out the timer in it) but this time make it a simple program and let windows scheduler wake it every 30min
3) Any other suggestion you may have
Techenologies available for me are VS 2008, SQLServer 2005
Scheduled task is the way to go. Jon wrote up a good summary of why services are not well suited for this sort of thing: http://weblogs.asp.net/jgalloway/archive/2005/10/24/428303.aspx
A service is easy to create and install and is more "professional" feeling so why not go that way? Using a non-service EXE would also work of course and would be slightly easier to get running (permissions, etc.) but I think the difference in setup between the two is nearly negligible.
One possible solution would be to add a timestamp column to your data tables.
Once this is done, you can have one entry in each table that has the last collected time by your contracted company. They can pull all records since that last time and update their records accordingly.
A Windows Service is more self contained, and you can easily configure it to start up automatically when the OS is starting up. You might also need to create additional configuration options, as well as some way to trigger the synchronization immediately.
It will also give you more room to grow your functionality for the service in the future.
A standalone app should be easier to develop though, however you are reliant on the windows scheduler to execute the task always. My experience has been that it is easier to mess up things with the windows scheduler and have it not run, for example in cases where you reboot the OS but no user has logged in.
If you want a more professional approach go with the service, even though it might mean a little bit more work.
A windows service makes more sense in this case. Think about what happens after your server is restarted:
With a Windows Application you need to have someone restart the application, or manually copy a shortcut to the startup folder to make sure the application gets launched
OR,
With a Windows Service you set it to start automatically and forget about it. When the machine reboots your service starts up and continues processing.
One more consideration, what happens when there is an error? A Windows application would likely show an error dialog and wait for input before continuing; whereas a service would log the error in the event log and carry on.
Related
I am having to design a client application that will be installed on all computers in our company that will collect and report hardware and software information for inventory purposes to a SQL database. The application may need to be updated remotely and possibly some parameters such as polling time period be updated remotely as well. I am not entirely sure of the best way to architect this type of application. In trying to research and think this through I have come up with the following options:
write a Windows Service that would always run automatically, anytime a computer booted up and on a Timer have it perform the necessary inventory functions.
write a Windows Service that acts like base platform for future expansions, but contain the actual inventory client in a Forms/WPF app that is minimized to the system tray and can be opened to change settings. The Windows Service would verify that the Forms/WPF app is always running and handle any management tasks such as possibly performing upgrades on the Forms/WPF app.
write just a Forms/WPF app that is configured to run on Startup. It would be minimized to the system tray and on a timer perform the inventory function and report to the database.
That is the three main options I have come up with. I'm hoping someone who has tackled a problem like this in the past can provide some insight into how they designed their project. Any advice is much appreciated.
In case anyone else has a similar question, the path I've ended up taking is to create a Windows Service that has all of its main logic in a separate dll and has a separate program for updating. The Update program stops the service, moves/overwrites the dll's for the service and then restarts the service. The main dll that the Service runs processes on a polling/timer feature and periodically checks for and downloads updates and then can schedule the Update program to run. I found a great example here.
Even though I've already chosen how I am going to implement this project, I am still open to hearing how others have handled similar situations.
I need to create an application that will run on a server and be able to be configured to run commands at certain times. For instance, there will be a web interface allowing a user to set an engage time and a disengage time. Once those values have been saved by the user I need for the server to be able to fire off those commands precisely at the time specified each day.
I would also need to be able to set single use non recurring events that would occur... maybe 10 minutes from the time an event was triggered and have a command fired off when that 10 minute timer goes off.
I've already got a class library written that has the engage and disengage commands exposed. I would hope to be able to integrate this into whatever solution I end up with and simply be able to make calls directly to the class. Alternatively I could also compile the class library into an executable and have commands issued to it via command line. I'm hoping to not have to do the latter.
I've never written anything like this before. I've peeked a bit at Windows Services, but there is a lot of chatter out there saying that it isn't necessarily the best option. Can someone please guide me in the right direction please?
A windows service is not a bad idea, its perfect for this kind of application. Unless you end up using standard windows scheduled tasks as the trigger for your command, you need some sort of process that is always running to contain your scheduler. A windows service is an excellent candidate for this.
Using a windows service in conjunction with Quartz.NET and some sort of persistence layer so you can store your schedules (in case you need to restart the service or it crashes etc) would be a good way to go.
Alternatively, you could write an application that just adds and removes windows scheduled tasks, but considering you have existing class libraries, using Quartz.NET will fit in well with your existing libraries.
easiest solution:
make a console exe and run under scheduled task in windows.
Let web page to accept user input and modify a configuration file.
So this is my first stint with programmatically creating windows service or scheduled tasks and I am confused which one to choose. I had a look at various articles like http://weblogs.asp.net/jgalloway/archive/2005/10/24/428303.aspx , scheduled task or windows service and some more but can' t really decide btween the two
Here is my scenario :
My application will pick up the code paths of a few dlls from the db , execute the DLLs using MSTest.exe and log back the results to the Db. this will probably be repeated every 2-3 hours . Now I am leaning a bit towards scheduled tasks since i won't have to worry about memory related issues but need some expert advice on this.
P.S. : The DLLs contain test methods that make calls to web services of applications deployed on various servers
Thanks in advance for the help
A Scheduled Task would be more appropiate for your scenario. I don't think it make a lot of sense building a scheduling mechanism on a windows service when OS already provides scheduling infraestructure.
A Windows service is more appropiate for processes that have to respond to events at any moment and not at specific and fix periods. That's why they are running all the time. An example of this is the SQL Server Service.
An exception of this could be a task that needs to run every second or so. In that corner case, a Window Service could be the best solution. For your specific schedule, I have no doubts that a scheduled task would fit much more better.
Although this post is several months old, here's a possible resolution in case it's helpful to others for the "Run whether the user is logged on or not" issue : start with a console project then change type to Windows App as mentioned at Run code once and exit formless app: Windows Forms or WPF... does it matter?:
“If you never show a UI, you should start with a WinForms project (WPF projects set extra project metadata that you don't want), then delete the reference to System.Windows.Forms.dll. Alternatively, start with a console project, then change the Output type to Windows Application.”
I am developing a asp.net site that needs hit a few social media sites daily for blanket friend/follower data. I have chosen arvixe business class as my hosting. In the future if we grow, I'd love to get onto a dedicated server and run a windows service, however since that is not in the cards at this point I need another reliable way of running scheduled tasks. I am familiar with running a thread timer from the app_code(global.aspx). However the app pool recycling will cause some problems with the timer. I have never used task scheduling like quartz but have read a lot about it on stackoverflow. I was looking for some advise as to how to approach my goal. One big problem I have using either method is that I will need the crawler threads to sleep for up to an hour regularly due to api call limits. My first thoughts were to use the db to save the starting and ending of a job. When the app pool recycles I would clear out any parts not completed and only start parts that do not have a record of running on that day. What do the experts here think? any good links to sample architecture of this type of scheduling?
It doesn't really matter what method you use, whether you roll your own or use Quartz. You are at the mercy of ASP.NET/IIS because that's where you want to host it.
Do you have a spare computer laying around that can just run a scheduled task and upload data to a hosted database? To be honest, it's possibly safer (depending on your use case) to just do it that way then try to run a scheduler in ASP.NET.
Somewhat along the lines of Bryan's post;
Find a spare computer.
Instead of allowing DB access have it call up a web service on your site. This service call should be the initiator of the process you are trying to do. Don't try to put params into it, just something like "StartProcess()" should work fine.
As far as going to sleep and resuming later take a look at Workflow Foundation. There are some nice built in features to persist state.
Don't expose your DB to the outside world, instead expose that page or web service and wraps some security around that. WCF has some nice built in security features for that.
The best part is when you decide to move off, you can keep your web service and have it called from a Windows Service in the same manner.
As long as you use a persistent job store (like a database) and you write and schedule your jobs so that they can handle things like being killed half way through, having IIS recycle your process is not that big a deal.
The bigger issue is that IIS shuts your site down if it doesn't have traffic. If you can keep your site up, then just make sure you set the misfire policy appropriately and that your jobs store any state data needed to pick up where they left off, you should be able to pull it off.
If you are language-agnostic and don't mind writing your "job-activation-script" in your favourite, Linux-supported language...
One solution that has worked very well for me is:
Getting relatively cheap, stable Linux hosting(from reputable
companies),
Creating a WCF service on your .Net hosted platform that will contain the logic you want to run regularly (RESTfully or SOAP or XMLRPC... whichever suits you),
Handling the calls through your Linux hosted cron jobs, written in your language of choice(I use PHP).
Working very well, like I said. No VPS expense,configurable and externally activated. I have one central place where my jobs are activated, with 99 to 100% uptime(never had any failures).
I have been working on many applications which run as windows service or scheduled tasks.
Now, i want to make sure that these applications will be fault tolerant and reliable. For example; i have a service that runs every hour. if the service crashes while its operating or running, i d like the application to run again for the same period (there are several things involved with this including transactions of data processing) , to avoid data loss. moreover, i d like the program to report the error with details. My goal is to avoid data loss and not falling behind for running the program.
I have built a class library that a user can import into a project. Library is supposed to keep information of running instance of the program, ie. program reads and writes information of running interval, running status etc. This data is stored in a database.
I was curious, if there are some best practices to make the scheduled tasks/ windows services fault tolerant and reliable.
Edit : I am talking about independent tasks or services which on different servers. and my goal is to make sure that the service will keep running, report any failures and recover from them.
I'm interested in what other people have to say, but I'll give you a few points that I've stumbled across:
Make an event handler for Unhandled Exceptions. This way you can clean up resources, write to a log file, email an administrator, or anything you need to instead of having it crash.
AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(AppUnhandledExceptionEventHandler);
Override any servicebase event handlers you need in the main part of your application. OnStart and OnStop are pretty crucial, but there are many others you can use. http://msdn.microsoft.com/en-us/library/system.serviceprocess.servicebase%28v=VS.71%29.aspx
Beware of timers. Windows forms timers won't work right in a service. User System.Threading.Timers or System.Timers.Timer. Best Timer for using in a Windows service
If you are updating on a thread, make sure you use a lock() or monitor in key sections to make sure everything is threadsafe.
Be careful not to use anything user specific, as a service runs without a specific user context. I noticed some of my SQL connection strings were no longer working for windows authorizations, etc. Also have heard people having trouble with mapped drives.
Never make a service with a UI. In fact for Vista and 7 they make it nearly impossible to do anyway. It shouldn't require user interaction, the most you can do is send a message with a WIN32 function. MSDN claims making interactive services is bad practice. http://msdn.microsoft.com/en-us/library/ms683502%28VS.85%29.aspx
For debugging purposes, it is way cool to make a service run as a console application until you get it doing what you want it to. Awesome tutorial: http://mycomponent.blogspot.com/2009/04/create-debug-install-windows-service-in.html
Anyway, hope that helps a little, but that is just a couple thing I poked around to find on my own.
Something obvious - don't run all your tasks at the same time. Try to schedule them so only one task is using some expensive resource at any time (if possible). For example, if you need to send out newsletters and some specific notifications, schedule them at different times. If two tasks need to clean up something in the database, let the one run after another.
Also schedule tasks to run outside of normal business hours - at night obviously.