I am maintaining a legacy Cloud Services application hosted on Azure targeting .net 4.6.1. Inside the Application_Start method of the Global.asax on the Web Role we are registering an event handler for RoleEnvironment.StatusCheck however our logs are demonstrating that this event call back is never being called or triggered.
According to this blog: https://convective.wordpress.com/2010/03/18/service-runtime-in-windows-azure/ we were expecting this event to be triggered every 15 seconds and we believe this was happening however has since stopped. We expect that the stopped working around the time we installed some new DLLs into the solution (some of these dlls include: Microsoft.Rest.ClientRuntime.dll, Microsoft.Azure.Storage.Common.dll, Microsoft.Azure.Storage.Blob.dll, Microsoft.Azure.KeyVault.dll)
We've tried RDP-ing onto the VM to check the event logs but nothing obvious is there. Any suggestions on where we may be able to search for clues?
It seems your event handler is not registered. Try below code with a different approach:
public class WorkerRole : RoleEntryPoint
{
public override bool OnStart()
{
RoleEnvironment.StatusCheck += RoleEnvironmentStatusCheck;
return base.OnStart();
}
// Use the busy object to indicate that the status of the role instance must be Busy
private volatile bool busy = true;
private void RoleEnvironmentStatusCheck(object sender, RoleInstanceStatusCheckEventArgs e)
{
if (this.busy)
{
// Sets the status of the role instance to Busy for a short interval.
// If you want the role instance to remain busy, add code to
// continue to call the SetBusy method
e.SetBusy();
}
}
public override void Run()
{
Trace.TraceInformation("Worker entry point called", "Information");
while (true)
{
Thread.Sleep(10000);
}
}
public override void OnStop()
{
base.OnStop();
}
}
Related
I am working with an Azure Service Bus Queue (or potentially a topic if required), and would like to know how a Web Job can be used with the Queue.
When a message comes onto the queue it represents a process that will run within the web job (or be started from the webjob). This process might be quick, 30 seconds, or it might be slow, 1 hour etc.
Can I use a single Web Job for this and somehow say that it should be running no more than 10 of these processes at a time?
Yes you can use a WebJob. I have created a simple WebJob with Storage Queue to just guide how it can be done. The below workflow will run only ten process at a time and keep all the other requests in memory of ConcurrentQueue. You will have to implement the logic to dequeue it and consume it
public class Functions
{
public delegate void CompletedProcessHandler(object sender, CompletedProcessHandlerArgs args);
static readonly Dictionary<int, CustomProcess> _dictionary =
new Dictionary<int, CustomProcess>();
static readonly ConcurrentQueue<ProcessEntity> _remaining =
new ConcurrentQueue<ProcessEntity>();
// This function will get triggered/executed when a new message is written
// on an Azure Queue called queue.
public static void ProcessQueueMessage([QueueTrigger("testqueue")] ProcessEntity msg,
TextWriter log)
{
if (_dictionary.Count <= 10)
{
var newProcess = new CustomProcess((_dictionary.Last().Key) + 1,
msg.Duration);
}
else
{
_remaining.Enqueue(msg);
}
}
public static void CompletedProcess(object sender, CompletedProcessHandlerArgs args)
{
_dictionary[Int32.Parse(args.ProcessID)].Dispose();
_dictionary.Remove(Int32.Parse(args.ProcessID));
}
}
public class CustomProcess : IDisposable
{
public event Functions.CompletedProcessHandler OnProcessCompleted;
private CancellationTokenSource _token;
private string _id;
private Timer _timer;
public CustomProcess(int i, int duration)
{
_timer = new Timer { Enabled = true, Interval = duration * 1000 };
_timer.Elapsed += Timer_Elapsed;
_id = i.ToString();
_token = new CancellationTokenSource();
Task.Factory.StartNew(() => WriteMessages());
_timer.Start();
OnProcessCompleted += Functions.CompletedProcess;
}
private void Timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
_token.Cancel();
OnProcessCompleted?.Invoke(this, new CompletedProcessHandlerArgs(_id));
}
private void WriteMessages()
{
while (!_token.Token.IsCancellationRequested)
{
Console.WriteLine("Test Message from process " + _id);
}
}
public void Dispose()
{
_token.Dispose();
_timer.Dispose();
}
}
public class CompletedProcessHandlerArgs : EventArgs
{
public string ProcessID { get; set; }
public CompletedProcessHandlerArgs(string ID)
{
ProcessID = ID;
}
}
public class ProcessEntity
{
public int Duration { get; set; }
}
In the app.config of the web job you need to provide the two app settings
<add name="AzureWebJobsDashboard"
connectionString="DefaultEndpointsProtocol=https;AccountName=[AccountName];AccountKey=[AccountKey]" />
<add name="AzureWebJobsStorage"
connectionString="DefaultEndpointsProtocol=https;AccountName=[AccountName];AccountKey=[AccountKey]" />
The Program file is the default one from the Visual Studio template
public class Program
{
// Please set the following connection strings in app.config for this WebJob to run:
// AzureWebJobsDashboard and AzureWebJobsStorage
static void Main()
{
var host = new JobHost();
// The following code ensures that the WebJob will be running continuously
host.RunAndBlock();
}
}
WebJob will keep dequeue the message the moment it comes. Since you want only 10 to run at a time you will have to enqueue the message in memory and wait for running process to complete before you start a new one
As #Rick has mentioned you can set the is_Singleton property to true in settings.job file of the web job
Yes, you can trigger a web job with an Azure Service Bus Queue or Topic. A good example to look at to get you going would be the Service Bus quick start project template in Visual Studio.
In particular, you want to look at the ServiceBusTrigger attribute that the Web Jobs SDK provides.
As for the scalability of the web job, this will scale according to your web app instances. So, if you had say 5 instances of your web app with always on enabled, then you would have 5 instances of your web job. As an additional comment on this, if you wanted just one instance of the web job in an environment of 5 web app instances, then you could set the is_singleton property to true in the settings.job file.
In an MVC / WebAPI environment I would use InRequestScope to bind the DbContext.
However, I am now on a Console application / Windows service / Azure worker role (doesn't really matter, just there's no Web request scope), which periodically creates a number of Tasks that run asynchronously. I would like each task to have its own DbContext, and since tasks run on their own thread, I tried binding DbContext using InThreadScope.
Unfortunately, I realize that the DbContext is not disposed when a task is finished. What actually happens is, the thread returns to the Thread Pool and when it is assigned a new task, it already has a DbContext, so DbContexts stay alive forever.
Is there a way InThreadScope can be used here or should I use some other scope? How can ThreadScope be used when threads are returning from ThreadPool every now and then?
If you decide to go on with custom scope, the solution is:
public sealed class CurrentScope : INotifyWhenDisposed
{
[ThreadStatic]
private static CurrentScope currentScope;
private CurrentScope()
{
}
public static CurrentScope Instance => currentScope ?? (currentScope = new CurrentScope());
public bool IsDisposed { get; private set; }
public event EventHandler Disposed;
public void Dispose()
{
this.IsDisposed = true;
currentScope = null;
if (this.Disposed != null)
{
this.Disposed(this, EventArgs.Empty);
}
}
}
Binding:
Bind<DbContext>().To<MyDbContext>().InScope(c => CurrentScope.Instance)
And finally:
using (CurrentScope.Instance)
{
// your request...
// you'll get always the same DbContext inside of this using block
// DbContext will be disposed after going out of scope of this using block
}
Azure role have RoleEnvironment.Stopping event that is raised when the role is being stopped. I discovered some issue in some unrelated code that needs special treatment in cases when the role is being stopped. Something like:
public class SomeFarAwayClass {
void someFarAwayFunction()
if( roleIsBeingStopped ) {
workSpecially();
} else {
workUsually();
}
}
}
Now I want to subscribe to RoleEnvironment.Stopping and in the event handler raise the roleIsBeingStopped permanently. Something like this:
public class SomeFarAwayClass {
//
private static bool roleIsBeingStopped = false;
public void SetBeingStopped() { roleIsBeingStopped = true; }
}
class MyRoleClass : RoleEntryPoint {
overribe bool OnStart()
{
RoleEnvironment.Stopping += stopping;
return base.OnStart();
}
void stopping(object sender, RoleEnvironmentStoppingEventArgs args)
{
SomeFarAwayClass.SetBeingStopped();
}
}
This solution implies that the role is never restarted in the same process, otherwise I'll need to reset the flag at some point. So far I've never seen Azure roles being restarted in the same process, it's a new process every time.
Can I be sure that once Azure role Stopping has been raised the role is never rerun in the same process?
I think you probably can, but at the same time you don't need to, because you also have the OnStart call you could use to re-set the flag.
I generally prefer to not rely on thing out of my control where I don't have to (of which there are many!), this would be one I'd avoid personally.
is there any way to change the status of the vm role instances from busy to ready.
I would like to do this with wcf service if it is possible.
Thanks a lot.
The Fabric Controller will check the status of your instance at regular intervals, and when doing so you'll be able to let it know if the instance is busy or not.
You'll simply need to handle the StatusCheck event and set it to busy (by calling the SetBusy method). Once you decide that the instance is ready (no longer busy), stop calling the SetBusy method.
public override bool OnStart()
{
RoleEnvironment.StatusCheck += RoleEnvironmentStatusCheck;
return base.OnStart();
}
// Use the busy object to indicate that the status of the role instance must be Busy
private volatile bool busy = true;
private void RoleEnvironmentStatusCheck(object sender, RoleInstanceStatusCheckEventArgs e)
{
If (this.busy)
{
// Sets the status of the role instance to Busy for a short interval.
// If you want the role instance to remain busy, add code to
// continue to call the SetBusy method
e.SetBusy();
}
}
Reference: http://msdn.microsoft.com/en-us/library/microsoft.windowsazure.serviceruntime.roleenvironment.statuscheck.aspx
I'm currently porting a WCF Service Project over to an Azure Role. Until now the library containing the service also hosted a Quartz.Net JobFactory for some lightweight background processing (perdiodically cleaning up stale email confirmation tokens). Do I have to move that code into a seperate worker role?
No you don't have to setup a separate worker role.
You simply have to start a background thread in your OnStart() Method of your Web Role. Give that thread a Timer object that executes your method after the given timespan.
Due to this you can avoid a new worker role.
class MyWorkerThread
{
private Timer timer { get; set; }
public ManualResetEvent WaitHandle { get; private set; }
private void DoWork(object state)
{
// Do something
}
public void Start()
{
// Execute the timer every 60 minutes
WaitHandle = new ManualResetEvent(false);
timer = new Timer(DoWork, null, TimeSpan.Zero, TimeSpan.FromMinutes(60));
// Wait for the end
WaitHandle.WaitOne();
}
}
class WebRole : RoleEntryPoint
{
private MyWorkerThread workerThread;
public void OnStart()
{
workerThread = new MyWorkerThread();
Thread thread = new Thread(workerThread.Start);
thread.Start();
}
public void OnEnd()
{
// End the thread
workerThread.WaitHandle.Set();
}
}
The answer above helped me a lot, but it has one hickup, the OnStart method is not overwritten so the method is never called. Also it should be Boolean and not void. This worked for me:
public override bool OnStart()
{
// For information on handling configuration changes
// see the MSDN topic at http://go.microsoft.com/fwlink/?LinkId=166357.
workerThread = new MyWorkerThread();
Thread thread = new Thread(workerThread.Start);
thread.Start();
return base.OnStart();
}