I have been given a task where it should be possible for a user to pass some information to a database table.
The table should be seen as a queue.
My question is:
Is it possible to execute some code on the webserver asynchronously, so the users can use the website for others tasks meanwhile processing the queue?
Is it possible to use the Thread class and how ?
Look into Asynchronous Pages as a start - it is teh easiest way to do what you describe.
http://msdn.microsoft.com/en-us/magazine/cc163725.aspx
You could use a service bus to get this done. If you feel up to it you could have a look at my open source esb:
http://shuttle.codeplex.com
It has an implementation that can use a sql table as a queue.
Related
I have a requirement where third party software running on a desktop will write to a local database and I need to send some of that information to a remote web service. I don't have any control over the thirdparty software that is doing the insert but I can read the database.
My approach is to have a windows service check the local table every second for an insert, if there is an insert send the webservice request. I don't like checking every second but this whole process needs to happen in a short amount of time after the insert. Is there a better way to go about this? Some kind of listener? I don't think I can use triggers.
This will be .NET and SQL Server if that matters.
Try using the SQLDependency class. Implement the onChange method of the class to handle your processing. The following article describes the process of configuring your environment and has some sample code for this.
http://www.codeproject.com/Articles/144344/Query-Notification-using-SqlDependency-and-SqlCach
I am using WebApi with Entity Framework to implement a REST service. I need to log the usage to the database. I can do this in the controller before it returns or in an ActionFilterAttribute. I want to be able to fire off a call to update the database, BUT I don't want to wait for completion. I want the response to return to the user without waiting for the update.
I was thinking about using a BackgroundWorker and passing in the objects.
Anyone have thoughts on if this is the good way to do this?
I think the question you should ask yourself is how much latency the database update can add to your overall response time. In most cases, it will be a lot simple to do the update as part of the request processing. Background worker is generally not a good solution but here is a good read related to that topic. If you absolutely need to do the database update outside of request processing, it will be better to consider a queueing mechanism like MSMQ, RabbitMQ, etc from the perspective of reliability.
I believe my performance problem is related to running in VS2012 debugger. When running the site directly, performance increased drastically. So I won't need to do any 'tuning tricks' if this proves out when deployed to test server.
Have you tried exploring NLog's async capabilities? We use NLog's async wrappers by wrapping a database logging target like so:
<targets async="true">
<target name="dbLog" xsi:type="Database" dbProvider="sqlserver" connectionString=".." />
.
.
</targets>
A quick startup on logging to MS SQL DB using NLog is found here
Moreover, you could make your logging method call async (.NET 4.5 required) and if you do not care for the result, choose not to await the method execution.
Look at this SO Thread for a sample NLog.config.
I have a program in which it insert a raw in a table after certain operations. I wan to call a web service in code behind to do some special tasks by the using of info that there is in the inserted row.
How I can do that?
Is it good idea to invoke this web service from a stored procedure or not? What are the other options?
More Details: Actually, I have an operation in my web application that take a long time to be completed and it is seriously time consuming operation. I don't want client wait until this process finish. That is why I decide write a web service to do this process in the background.
Therefore, I think it may be a good idea that when client request receive I insert his request in a table and call a web service to handle it. Moreover, I do not want to wait until web service return the result, so I will aware client from its result through the report. I do not know what is the best solution to handle it.
I usually keep myself far away from table triggers(it sounds like you're about to use an on insert trigger for a table).
I don't know your specific situation but you could either :
Call the webservice before or after you call the stored procedure, this way the data layer(stored proc) only handles data and nothing more. You're logical layer will handle the logic of calling an extra webservice.
Write a service that will periodicly read a table and notify the webservice of the latest modifications. More messy but it resembles more the effect you're trying to achieve.
There are probably more solutions but i'd need more information on what it exactly is you're doing. Right now it's kinda vague :)
It is never a good idea to call webservice from Stored procs or other DB objects. You can call it from your code, just after you execute the insert and commit it.
The problem it sounds like is that you cannot guarantee that the web service will be called unless you call it before committing the transaction. However, it sounds like the web service needs to be called after commit. In this case, it sounds like you should use a message queue. You could either build one in your database or you could use one off the shelf (http://aws.amazon.com/sqs/ or http://www.windowsazure.com/en-us/home/features/messaging/).
The steps would be:
Insert message into queue (after this is success you can return the call, depending on what your contract with the caller is)
Read message
Insert into table
Call web service
Delete message
The downside is that you will need to make the operations (inserting into the table and calling the web service) idempotent.
Team:
I need to invoke a WF activity (XAML) from a WF service (XAMLX) asynchronously. I am already referencing the Microsoft.Activities.Extensions framework and I'm running on the Platform Update 1 for the state machine -- so if the solution is already in one of those libraries I'm ready!
Now, I need to invoke that activity (XAML) asynchronously -- but it has an output parameter that needs to set a variable in the service (XAMLX). Can somebody please provide me a solution to this?
Thanks!
* UPDATE *
Now I can post pictures, * I think *, because I have enough reputation! Let me put a couple out here and try to better explain my problem. The first picture is the WF Service that has the two entry points for the workflow -- the second is the workflow itself.
This workflow is an orchestration mechanism that constantly restarts itself, and has some failover mechanisms (e.g. exit on error threshold and soft exit) so that we can manage our queue of durable transactions using WF!
Now, we had this workflow working great when it was all one WF Service because we could call the service, get a response back and send the value of that response back into another entry point in a trigger to issue a soft exit. However, a new requirement has arrisen asking us to make the workflow itself a WF activity in another project and have the Receive/Send-Reply sequences in the WF Service Application project.
However, we need to be able to startup this workflow and forget about it -- then let it know somehow that a soft exit is necessary later on down the road -- but since WF executes on a single thread this has become a bit challenging at best.
Strictly speaking in XAML activities Parallel and ParallelForEach are how you perform asynchrony.
The workflow scheduler only uses a single thread (much like UI) so any activity that is running will typically be running on the same thread, unless it implements AsyncCodeActivity, in which case you are simply handing back the scheduler thread to the runtime while waiting for a callback from whichever async code your AsyncCodeActivity implementation is calling.
Therefore are you sure this is what you want to achieve? Do you mean you want to run it after you have sent your initial response? In this case place your activity after the Send Reply.
Please provide more info if these suggestions don't answer your question./
Update:
The original requirement posed (separating implementation from the service Receive/Send activities) may actually be solved by hosting the target activity as a service. See the following link
http://blog.petegoo.com/index.php/2011/09/02/building-an-enterprise-workflow-system-with-wf4/
Problem: Some 300 candidates make a test using Flex. A test consist of some 100 exercises. After each exercise a .NET service is called to store the result. If a candidate finishes a test, all the data of his/her test is denormalized by Asp.NET. This denormalization can take some cpu and can take 5 to 10 seconds. Now, most of the times, some of the candidates have finished their test earlier than the rest, but still some 200 of them wait until their time is up. At that moment, 200 candidates finish their test and 200 sessions are denormalized at the same time. At this point, server load (cpu) is too high and cause calls to the webserver to go wrong. Now, instead of all these sessions being normalized concurrently, I would like to add them to a queue using MSMQ.
Question:
How do you process the Queue?
Do you start a separate thread in the Application_Start of global.asax that listens to the queue? If there are messages, they are dealt one at the time.
Is it necessary to do this in a separate thread? What if in the global.asax you just call a singleton for instance that starts listening to the queue? In what thread will this singleton run? (what's the thread that calls global.asax)
What are best practices to implement this? Links? Resources? Tutorials? Examples?
I don't like the idea, but could you put an exe on the root of your website, an exe that starts a process listening to the queue...
If you get a message out of the queue, do you remove it when you pull it out or do you remove it if denormalization for this session was successful? If you remove it when you pull it out and something goes wrong...
I could also create my own queue in memory, but restarting the webserver would empty the queue and a lot of sessions would end up not being normalized, so I guess this is really a bad idea.
Is MSMQ a good choice or are there better alternatives?
You could consider using a WCF-Service with MSMQ transport. I used this approach in an application that calculates commissions:
User completes asp.net wizard configuring calculation parameters
Calculation Job is sent to WCF-Service using MSMQ transport
Service transaction is completed as soon as Job entered MSMQ
New transaction scope is created for processing Job instances
One drawback is that the transaction will require MSDTC which will add some overhead when targeting MS SQL Server and even more when dealing with Oracle.
IDesign provides a lot of useful samples and best practices on WCF queueing.
Personally, I use a servicebus for scenario's like that. I know this sounds like an overkill, but I think the .net servicebusses are so good that they require the least amount of code written by you, because it's not easy to create a good scheduler for background processes without disturbing the threads of the application pool the webapp is running in. NServicebus and MassTransit are both good an well enough documented servicebuses for your scenario. With a servicebus, you have a framework that writes to msmq and listens to msmq in several apps connected by the messagequeue. The bus makes it easy for you to create a separate app that runs as a background service and is connected with your web-app by the message queue. When you use topself (included in nservicebus and masstransit), an installer/uninstaller for the seperate apps is automatically generated by the service bus.
Question: Why don't you like the idea of having a separate exe?
How do you process the Queue?
Do you start a separate thread in the Application_Start of global.asax
that listens to the queue? If there are messages, they are dealt one at
the time.
Is it necessary to do this in a separate thread? What if in the
global.asax you just call a singleton for instance that starts listening to
the queue? In what thread will this singleton run? (what's the thread that
calls global.asax)
[skip]
I don't like the idea, but could you put an exe on the root of your website, an exe that > starts a process listening to the queue...
Normally another program processes the queue - not ASP.NET. Either a windows service or an executable that you run under a scheduler (and there's no reason to put it in the root of your website).
If you get a message out of the queue, do you remove it when you pull
it out or do you remove it if denormalization for this session was
successful? If you remove it when you pull it out and something goes
wrong...
For critical work, you perform a transactional read. Items aren't removed from the queue until you commit your read operation, but while the transaction is open, no other process can get the item.
What are best practices to implement this? Links? Resources? Tutorials? Examples?
This tutorial is a good introduction and John Breakwell's blog is excellent and offers a lot of good links (including the ones in his easy-to-find sidebar "MSMQ Documentation").