I have a state machine workflow with two states
- Employee Request
- Manager Approval
In Employee request I save the request to the database through code activity and genereate
a request number
How I get those outputs after calling WorkflowApplication.Run()
You will need to setup callbacks to WorkflowApplication actions:
WorkflowApplication Application;
//...
// Setup callbacks
this.Application.Completed += OnApplicationCompleted;
// Run the application
this.Application.Run();
Then implement OnApplicationCompleted like this:
void OnApplicationCompleted(WorkflowApplicationCompletedEventArgs e)
{
switch (e.CompletionState)
{
case ActivityInstanceState.Closed:
// Application finished correctly
// Get outputs
var output1 = e.Outputs["NameOfOutput"];
break;
case ActivityInstanceState.Canceled:
// Application was cancelled before completion
break;
case ActivityInstanceState.Faulted:
// Application throw an exception and was shut down
break;
}
}
All of this is covered on this page: http://msdn.microsoft.com/en-us/library/dd560894%28v=vs.110%29.aspx
Related
I'm using Durable Functions in a process to collect data from 12 different people. For this I chose the WaitForExternalEvent method. I need to get notified of those external events as they happen. All events must be received in the next 1h.
I have created the following orchestration. The behaviour is odd however. The orchestration neither completes, nor fails. I am using Durable Functions Monitor (dfMon) to inspect the logs. As you can see in the execution history all 12 events are in fact received (before the 1h timeout). Still the orchestrator:
didn't execute the Fxbm_notifyOfNewReport activity function after each received event
also didn't exit the while loop after all 12 events
Also, more than 1h has elapsed and every timeout timer has fired. Still, no exception was thrown. The orchestration is still in a running state.
I took inspiration for this from this doc and this blog.
Does someone know why I am not seeing the expected behaviour?
public class Fxbm_workflow
{
[FunctionName(nameof(Fxbm_workflow))]
public async Task Run([OrchestrationTrigger] IDurableOrchestrationContext ctx, ILogger log)
{
var id = ctx.InstanceId;
var trigger = ctx.GetInput<Trigger<OrchestrationInput2>>();
// sub-orchestration to distribute data to people
// return value is int[], these are the ids of the people
var input = (trigger, id);
var childWorkflowId = $"{id}_{nameof(Fxbm_prep_workflow)}";
var requiredCompanies = await ctx.CallSubOrchestratorAsync<int[]>(nameof(Fxbm_prep_workflow), instanceId: childWorkflowId, input: input);
// to every distributed data package, a string response is expected in 1h at the latest
var expiresIn = TimeSpan.FromHours(1);
var responseTasks = requiredCompanies.Select(id => ctx.WaitForExternalEvent<string>(id.ToString(), expiresIn)).ToList();
// all tasks need to complete or a timeout exception must be thrown
// I want to get notified of responses as they come in
// therefore Task.WhenAll() is not suitable
while (responseTasks.Any())
{
try
{
// responses as they occur
var receivedResponse = await Task.WhenAny(responseTasks);
responseTasks.Remove(receivedResponse);
var stringResponse = await receivedResponse;
// notify via mail
await ctx.CallActivityAsync(nameof(Fxbm_notifyOfNewReport), stringResponse);
}
catch (TimeoutException)
{
// break;
throw;
}
}
}
}
I'm working on a basic (non DB) connection pool which allows only 1 connection to be created per project.
The connection pool supports an async-task/threaded environment and therefor I have made use of a semaphore instead of a regular Lock.
I wrote a test, below, which is meant to stress test the connection pool.
The code works but under higher loads, the semaphore throws the following error
I can overcome this error by decreasing the load.
For example, increasing the _waitTimeMs to a higher number (i.e. 50ms or 100ms or 1000ms) or decreasing _numberOfTasks (i.e. to 5 or 3).
I should also mention that sometimes, it manages to run higher load tests without errors.
Is there a mistake or misconception in my code and/or use of semaphores?
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
internal class Program
{
static int _numberOfTasks = 50;
static int _waitTimeMs = 1;
static SemaphoreSlim _dictLock = new SemaphoreSlim(1, 1);
static ConcurrentDictionary<string, bool> _pool = new ConcurrentDictionary<string, bool>();
/// <summary>
/// Only 1 connection allowed per project.
/// We reuse connections if available in pool, otherwise we create 1 new connection.
/// </summary>
static async Task<string> GetConnection(string projId)
{
try
{
// Enter sema lock to prevent more than 1 connection
// from being added for the same project.
if (await _dictLock.WaitAsync(_waitTimeMs))
{
// Try retrieve connection from pool
if (_pool.TryGetValue(projId, out bool value))
{
if (value == false)
return "Exists but not connected yet.";
else
return "Success, exists and connected.";
}
// Else add connection to pool
else
{
_pool.TryAdd(projId, false);
// Simulate delay in establishing new connection
await Task.Delay(2);
_pool.TryUpdate(projId, true, false);
return "Created new connection successfully & added to pool.";
}
}
// Report failure to acquire lock in time.
else
return "Server busy. Please try again later.";
}
catch (Exception ex)
{
return "Error " + ex.Message;
}
finally
{
// Ensure our lock is released.
_dictLock.Release();
}
}
static async Task Main(string[] args)
{
if (true)
{
// Create a collection of the same tasks
List<Task> tasks = new List<Task>();
for (int i = 0; i < _numberOfTasks; i++)
{
// Each task will try to get an existing or create new connection to Project1
var t = new Task(async () => { Console.WriteLine(await GetConnection("Project1")); });
tasks.Add(t);
}
// Execute these tasks in parallel.
Parallel.ForEach<Task>(tasks, (t) => { t.Start(); });
Task.WaitAll(tasks.ToArray());
Console.WriteLine("Done");
Console.Read();
}
}
}
Is there a mistake or misconception in my code and/or use of semaphores?
There's a bug in your code, yes. If the WaitAsync returns false (indicating that the semaphore was not taken), then the semaphore is still released in the finally block.
If you must use a timeout with WaitAsync (which is highly unusual and questionable), then your code should only call Release if the semaphore was actually taken.
I have setup a SignalR hub which has the following method:
public void SomeFunction(int SomeID)
{
try
{
Thread.Sleep(600000);
Clients.Caller.sendComplete("Complete");
}
catch (Exception ex)
{
// Exception Handling
}
finally
{
// Some Actions
}
m_Logger.Trace("*****Trying To Exit*****");
}
The issue I am having is that SignalR initiates and defaults to Server Sent Events and then hangs. Even though the function/method exits minutes later (10 minutes) the method is initiated again ( > 3 minutes) even when the sendComplete and hub.stop() methods are initiated/called on the client prior. Should the user stay on the page the initial "/send?" request stays open indefinitely. Any assistance is greatly appreciated.
To avoid blocking the method for so long, you could use a Taskand call the client method asynchronously.
public void SomeFunction(Int32 id)
{
var connectionId = this.Context.ConnectionId;
Task.Delay(600000).ContinueWith(t =>
{
var message = String.Format("The operation has completed. The ID was: {0}.", id);
var context = GlobalHost.ConnectionManager.GetHubContext<SomeHub>();
context.Clients.Client(connectionId).SendComplete(message);
});
}
Hubs are created when request arrives and destroyed after response is sent down the wire, so in the continuation task, you need to create a new context for yourself to be able to work with a client by their connection identifier, since the original hub instance will no longer be around to provide you with the Clients method.
Also note that you can leverage the nicer syntax that uses async and await keywords for describing asynchronous program flow. See examples at The ASP.NET Site's SignalR Hubs API Guide.
I have a self-hosted application akin to a scenario wherein I have a method that continuously broadcasts to groups (whether somebody has "joined" or not). Something like:
var aTimer = new System.Timers.Timer(2000);
aTimer.Elapsed += (sender, e) =>
{
// broadcast to listeners whether they are listening or not
IHubConnectionContext _clients = GlobalHost.ConnectionManager.GetHubContext<ChatHub>().Clients;
_clients.Group("group1FixedName").showMessage("Some message for group 1 only");
_clients.Group("group2FixedName").showMessage("Some message for group 2 only");
// etc
};
aTimer.Start();
I had recently upgraded to version 1.1.0 from beta1. I started to observe that the "remove" method doesn't work as the "client" (web browser) is still receiving messages from the "other" group even if I initiated a "leave". Note that "leaving" the group doesn't mean closing the web browser. It's still in the same page (Single Page Application) and leaving/joining a group is triggered by a selection (combo box for example).
Code in hub:
public Task Leave(string groupName)
{
return Groups.Remove(Context.ConnectionId, groupName)
.ContinueWith(z => Clients.Caller.showCallerMessage("You are now leaving " + groupName));
}
Code in javascript client to "leave the group":
chat.server.leave("group1FixedName");
Code in javascript client to "join the group":
chat.server.join("group1FixedName");
Code in Hub for joining:
public Task Join(string groupName)
{
return Groups.Add(Context.ConnectionId, groupName)
.ContinueWith(z => Clients.Caller.showCallerMessage("You are now listening to " + groupName));
}
Is there something wrong with my implementation here?
This is bug #2040 introduced in 1.1.0beta.
Team is working on fixing it.
I am using MassTransit request and response with SignalR. The web site makes a request to a windows service that creates a file. When the file has been created the windows service will send a response message back to the web site. The web site will open the file and make it available for the users to see. I want to handle the scenario where the user closes the web page before the file is created. In that case I want the created file to be emailed to them.
Regardless of whether the user has closed the web page or not, the message handler for the response message will be run. What I want to be able to do is have some way of knowing within the response message handler that the web page has been closed. This is what I have done already. It doesnt work but it does illustrate my thinking. On the web page I have
$(window).unload(function () {
if (event.clientY < 0) {
// $.connection.hub.stop();
$.connection.exportcreate.setIsDisconnected();
}
});
exportcreate is my Hub name. In setIsDisconnected would I set a property on Caller? Lets say I successfully set a property to indicate that the web page has been closed. How do I find out that value in the response message handler. This is what it does now
protected void BasicResponseHandler(BasicResponse message)
{
string groupName = CorrelationIdGroupName(message.CorrelationId);
GetClients()[groupName].display(message.ExportGuid);
}
private static dynamic GetClients()
{
return AspNetHost.DependencyResolver.Resolve<IConnectionManager>().GetClients<ExportCreateHub>();
}
I am using the message correlation id as a group. Now for me the ExportGuid on the message is very important. That is used to identify the file. So if I am going to email the created file I have to do it within the response handler because I need the ExportGuid value. If I did store a value on Caller in my hub for the web page close, how would I access it in the response handler.
Just in case you need to know. display is defined on the web page as
exportCreate.display = function (guid) {
setTimeout(function () {
top.location.href = 'GetExport.ashx?guid=' + guid;
}, 500);
};
GetExport.ashx opens the file and returns it as a response.
Thank you,
Regards Ben
I think a better bet would be to implement proper connection handling. Specifically, have your hub implementing IDisconnect and IConnected. You would then have a mapping of connectionId to document Guid.
public Task Connect()
{
connectionManager.MapConnectionToUser(Context.ConnectionId, Context.User.Name);
}
public Task Disconnect()
{
var connectionId = Context.ConnectionId;
var docId = connectionManager.LookupDocumentId(connectionId);
if (docId != Guid.Empty)
{
var userName = connectionManager.GetUserFromConnectionId(connectionId);
var user = userRepository.GetUserByUserName(userName);
bus.Publish( new EmailDocumentToUserCommand(docId, user.Email));
}
}
// Call from client
public void GenerateDocument(ClientParameters docParameters)
{
var docId = Guid.NewGuid();
connectionManager.MapDocumentIdToConnection(Context.ConnectionId, docId);
var command = new CreateDocumentCommand(docParameters);
command.Correlationid = docId;
bus.Publish(command);
Caller.creatingDocument(docId);
}
// Acknowledge you got the doc.
// Call this from the display method on the client.
// If this is not called, the disconnect method will handle sending
// by email.
public void Ack(Guid docId)
{
connectionManager.UnmapDocumentFromConnectionId(connectionId, docId);
Caller.sendMessage("ok");
}
Of course this is from the top of my head.