I am creating a Windows Service app that I would like to have programmatically pause when either a system error, odbc connection, or missing file error occur while . I was wondering if anyone knows how to do this? The Windows service app uses an odbc connection and datareader to connect to an MS Access database and an Oracle table, so there are the probable errors that I would be handling with those, I just want to allow a pause for the user handle the errors if/when they occur.
ServiceController service = new ServiceController(serviceName);
TimeSpan timeout = TimeSpan.FromMilliseconds(timeoutValue);
service.Pause(); //or whatever you want here.
sevice.WaitForStatus(ServiceControllerStatus.Paused, timeout);
...
Then to restart, do the same thing except for
service.Continue();
sevice.WaitForStatus(ServiceControllerStatus.Running, timeout);
You can do this for any state you want. Check out the msdn documentation by googling SeviceController. It will be the first result returned.
Also, you will need to handle the OnPause and OnContinue events in your service.
Have you tried?
System.Threading.Thread.Sleep(1000); // sleep for 1 second
Adjust the 1000 to 1000 times however long you want it to sleep in seconds.
Assuming that your service has a continual loop that checks for data, add a check to an external source for pause/continue commands. This source can be a message queue like MSMQ or a database table.
I implemented something along like this by having my service continually check a table for commands, and reporting its status in another table. When it gets a start command it launches a processing loop on another thread. A stop command causes it to signal the thread to gracefully exit. The service core never stops running.
The user interacts via a separate app with a UI that lets them view the service's status and submit commands. Since the app does its control via a database it doesn't have to run on the same machine that the service is running on.
Related
I am writing an API using ASP.NET and I have some potentially long running code from the different end points. The system uses CQRS and Event Sourcing. A Command comes into to an end point and is then published as an event using MediatR. However the Handlers are potentially long running. Since some of the Requests coming in might be sent to multiple Handlers. This process could take longer than the 12s that AWS allows before returning an Error code.
Is there a way to return a response back to the caller to say that the event has been created while still contining with the process? That is to say fire off a separate task that performs the long running piece of code, that also catches and logs errors. Then return a value back to the user saying the Event has been successfully created?
I believe that ASP.NET spins up a new instance each time a call is made, will the old instance die one a value is returned, killing the task?
I could be wrong with a number of points here, this is my knowledge gleaned from the internet but I could have missunderstood articles.
Thanks.
Yes, you should pass the long-running task off to a background process and return to the user. When the task is complete, notifiy the user with whatever mechanism is appropriate for your site.
But do not start a new thread, what you want is to have a background service running for this, and use that to manage your request.
If a new thread is running the long operation it will remain “open/live” until it finishes. Also you can configure the app pool to always be active.
There are a lot of frameworks to work with long running tasks like Hangfire.
And to keep the user updated with the status of the task you can use SignalR to push notifications to the UI
We're using ActiveMQ locally to transfer data between 5 processes that turn simultaneously.
I have some data I need to send to a process, both at runtime (which works perfectly fine), but also a default value on start. Thing is it is published when the process starts, it just doesn't read because it wasn't subscribed to the topic at the time the data was sent.
I have multiple solutions : I could delay the first publishing for a moment so that the process has time to launch (which doesn't seem very appealing) ; or is there a way to send all stored previously non-treated messages to some process that just subscribed ?
I'm coding in C#.
I don't have any experience with ActiveMQ, but other message system usually have an option which marks the subscription as persistent, which means that; after the first subscription; the message queue itself checks if a certain message is delivered to that system and retries with a timeout. In this scenario you need to start the receiver at least 1 time.
If this is not an option and you want to plug in receiver afterwards, you might want to consider a setup of your messages which allows you to retrieve the full state, i.e. if you send total-messages instead of differential- messages.
After a little google, I came upon this definition durable subscribers, I hope this helps:
See:
http://activemq.apache.org/how-do-durable-queues-and-topics-work.html
and
http://activemq.apache.org/manage-durable-subscribers.html
since you are using C# client i don't konw if this is supported
topic = new ActiveMQTopic("TEST.Topic?consumer.retroactive=true");
http://activemq.apache.org/retroactive-consumer.html
So, another solution is to configure this behavior on the broker side by adding that to the activemq.xml and restart :
The subscription recovery policy allows you to go back in time when
you subscribe to a topic.
<destinationPolicy>
<policyMap>
<policyEntries>
<policyEntry topic=">" >
<subscriptionRecoveryPolicy>
<timedSubscriptionRecoveryPolicy recoverDuration="10000" />
<fixedCountSubscriptionRecoveryPolicy maximumSize="10000" />
</subscriptionRecoveryPolicy>
</policyEntry>
</policyEntries>
</policyMap>
</destinationPolicy>
http://activemq.apache.org/subscription-recovery-policy.html
I went around the issue by sending a message from each process when they're launched back to the main one, and then only sending the info I needed to send.
I have created a windows service using c#.NET, The service will updated oracle tables whenever it receives new files. I have kept timer control and the time limit as 30 seconds. I am using ODP.NET as data access layer.
The very first time I will get error, but subsequently the service will work fine. If service is Idle for a long time if it receives a file, I will get "connection lost error", but after if we receives file it will loaded successfully.
Kindly suggest me do I need add any properties in connection string to fix this error?
Hello Karthik Two issues here it seems.
You are best to open and close a new connection each time your service is called.
Windows services quickly go to a latent state if not called and they will respond slower on the next call. If the caller does not have a sufficient timeout value to accomodate this lag then it will return a time out error. If you address these two points you should be fine.
I want to create a thread on user_login Event or Form_load Event.
In this thread i want to call a class function to execute some sql statement, and the user do not have to wait for the result or background process to be finished, he is just directed to his desired page let say my profile or what ever.
I am using ASP.NET, C#.
For what it is worth, this is a Bad Idea. There are a variety of ways that that IIS could terminate that background thread (IIS restart, app pool restart, etc., all of which are normal expected behavior of IIS), and the result would be that your DB transaction gets silently rolled back.
If these queries need to be reliably executed, you should either execute them in the request or send them to a windows service or other long-lived process. This doesn't mean that the user can't get feedback on the progress- the IIS request itself could be executed via an AJAX call.
Here are some examples of asynchronous calls in C#.
http://support.microsoft.com/kb/315582
The choice of pattern depends on your needs. Note that in sample 5 you can provide null as the callback if you don't want any code executed when the action is done.
You could do this by calling your method in a thread using Thread.Start. IsBackground is false by default, which should prevent your application from stopping.
http://msdn.microsoft.com/en-us/library/7a2f3ay4.aspx
But, since most of your time will probably be spent in your database call. Why not just execute it asynchronously without a callback? On a SqlCommand that would be BeginExecuteNonQuery.
Quick summary with what I now know
I've got an EventWaitHandle that I created and then closed. When I try to re-create it with this ctor, an "Access to the path ... is denied" exception is thrown. This exception is rare, most of the times it just re-creates the EventWaitHandle just fine. With the answer posted below (by me), I'm able to successfully call EventWaitHandle.OpenExisting and continue on in the case that an exception was thrown, however, the ctor for EventWaitHandle should have done this for me, right? Isn't that what the out parameter, createdNew is for?
Initial question
I've got the following architecture, a windows service and a web service on the same server. The web service tells the windows service that it has to do work by opening and setting the wait handle that the windows service is waiting on.
Normally everything is flawless and I'm able to start / stop the windows service without any issue popping up. However, some times when I stop the web service and then start it up again, it will be completely unable to create the wait handle, breaking the whole architecture.
I specifically need to find out what is breaking the event wait handle and stop it. When the wait handle "breaks", I have to reboot windows before it will function properly again and thats obviously not ideal.
UPDATE: Exception thrown & Log of Issue
I rebooted the windows service while the web service was doing work in hopes of causing the issue and it did! Some of the class names have been censored for corporate anonymity
12:00:41,250 [7] - Stopping execution due to a ThreadAbortException
System.Threading.ThreadAbortException: Thread was being aborted.
at System.Threading.Thread.SleepInternal(Int32 millisecondsTimeout)
at OurCompany.OurProduct.MyClass.MyClassCore.MonitorRequests()
12:00:41,328 [7] - Closing Event Wait Handle
12:00:41,328 [7] - Finally block reached
12:00:42,781 [6] - Application Start
12:00:43,031 [6] - Creating EventWaitHandle: Global\OurCompany.OurProduct.MyClass.EventWaitHandle
12:00:43,031 [6] - Creating EventWaitHandle with the security entity name of : Everyone
12:00:43,078 [6] - Unhandled Exception
System.UnauthorizedAccessException: Access to the path 'Global\OurCompany.OurProduct.MyClass.EventWaitHandle' is denied.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.Threading.EventWaitHandle..ctor(Boolean initialState, EventResetMode mode, String name, Boolean& createdNew, EventWaitHandleSecurity eventSecurity)
at OurCompany.OurProduct.MyClassLibrary.EventWaitHandleFactory.GetNewWaitHandle(String handleName, String securityEntityName, Boolean& created)
at OurCompany.OurProduct.MyClassLibrary.EventWaitHandleFactory.GetNewEventWaitHandle()
at OurCompany.OurProduct.MyClass.MyClassCore..ctor()
Rough timeline:
11:53:09,937: The last thread on the web service to open that existing wait handle, COMPLETED its work (as in terminated connection with the client)
12:00:30,234: The web service gets a new connection, not yet using the wait handle. The thread ID for this connection is the same as the thread ID for the last connection at 11:53
12:00:41,250: The windows service stops
12:00:42,781: The windows service starts up
12:00:43,078: The windows service finished crashing
12:00:50,234: The web service was actually able to open the wait handle call Set() on it without any exception thrown etc.
12:02:00,000: I tried rebooting the windows service, same exception
12:36:57,328: After arbitrarily waiting 36 minutes, I was able to start the windows service up without a full system reboot.
Windows Service Code
Initialization:
// I ran into security issues so I open the global EWH
// and grant access to Everyone
var ewhSecurity = new EventWaitHandleSecurity();
ewhSecurity.AddAccessRule(
new EventWaitHandleAccessRule(
"Everyone",
EventWaitHandleRights.Synchronize | EventWaitHandleRights.Modify,
AccessControlType.Allow));
this.ewh = new EventWaitHandle(
false,
EventResetMode.AutoReset,
#"Global\OurCompany.OurProduct.MyClass.EventWaitHandle",
out created,
ewhSecurity);
// the variable "created" is logged
Utilization:
// wait until the web service tells us to loop again
this.ewh.WaitOne();
Disposal / closing:
try
{
while (true)
{
// entire service logic here
}
}
catch (Exception e)
{
// should this be in a finally, instead?
if (this.ewh != null)
{
this.ewh.Close();
}
}
Web Service Code
Initialization:
// NOTE: the wait handle is a member variable on the web service
this.existing_ewh = EventWaitHandle.OpenExisting(
#"Global\OurCompany.OurProduct.MyClass.EventWaitHandle");
Utilization:
// wake up the windows service
this.existing_ewh.Set();
Since the EventWaitHandle is a member variable on the web service, I don't have any code that specifically closes it. Actually, the only code that interacts with the EventWaitHandle on the web service is posted above.
Looking back, I should probably have put the Close() that is in the catch block, in a finally block instead. I probably should have done the same for the web service but I didn't think that it was needed.
At any rate, can anyone see if I'm doing anything specifically wrong? Is it crucially important to put the close statements within a finally block? Do I need to manually control the Close() of the existing_ewh on the web service?
Also, I know this is a slightly complex issue so let me know if you need any additional info, I'll be monitoring it closely and add any needed information or explanations.
Reference material
EventWaitHandleSecurity Class
EventWaitHandleAccessRule Class
EventWaitHandle Class
In the code that creates the wait handle on the windows service, if it fails (as in access denied), you could try to "open an existing wait handle" via
EventWaitHandle.OpenExisting(
#"Global\OurCompany.OurProduct.MyClass.EventWaitHandle",
EventWaitHandleRights.Synchronize | EventWaitHandleRights.Modify);
Though, I'm not entirely sure if the behaviour would stay the same at that point.
Note: I'd appreciate feedback. Its a potential answer so I'm answering my own question, again, plenty of comments are quite welcome!
Note 2: Amazingly, applying EventWaitHandleRights.FullControl instead of the above flags (Synchronize + Modify) doesn't work well. You must use the sample above.
MSDN says:
UnauthorizedAccessException - The named event exists and has access control security, but the user does not have EventWaitHandleRights.FullControl.
and
The caller has full control over the newly created EventWaitHandle object even if eventSecurity denies or fails to grant some access rights to the current user.
Your service has no rights to get the existing event via EventWaitHandle constructor. (EventWaitHandleRights.FullControl is not specified. And your named event exists while it has opened handles on it.) You can open the existing event using EventWaitHandle.OpenExisting.