Why does the workflow need a httpcontext?

[weirdyang]

I'm trying to trigger a workflow using a message from a kafka queue, but it fails at the log task:

"An unhandled error occurred while executing an activity. Workflow ID: '18'. Activity: '4mexqzdhk7tpj055nckpytq1dm', 'LogTask'. 
Putting the workflow in the faulted state.", "callSite": "OrchardCore.Workflows.Services.WorkflowManager.ExecuteWorkflowAsync", "exception": "Value cannot be null. (Parameter 'httpContext')", "stacktrace": "   
at Microsoft.AspNetCore.Mvc.ActionContext..ctor(HttpContext httpContext, RouteData routeData, ActionDescriptor actionDescriptor, ModelStateDictionary modelState)\r\n 
  at OrchardCore.DisplayManagement.Liquid.LiquidViewTemplateExtensions.GetActionContextAsync(HttpContext httpContext)\r\n 
  at OrchardCore.DisplayManagement.Liquid.LiquidViewTemplateExtensions.GetViewContextAsync(LiquidTemplateContext context)\r\n  
 at OrchardCore.DisplayManagement.Liquid.LiquidViewTemplateExtensions.RenderAsync(LiquidViewTemplate template, TextEncoder encoder, LiquidTemplateContext context, Object model)\r\n  
 at OrchardCore.Workflows.Expressions.LiquidWorkflowExpressionEvaluator.EvaluateAsync[T](WorkflowExpression`1 expression, WorkflowExecutionContext workflowContext, TextEncoder encoder)\r\n 
  at OrchardCore.Workflows.Activities.LogTask.ExecuteAsync(WorkflowExecutionContext workflowContext, ActivityContext activityContext)\r\n   
at OrchardCore.Workflows.Services.WorkflowManager.ExecuteWorkflowAsync(WorkflowExecutionContext workflowContext, ActivityRecord activity)" }

OrchardCore/src/OrchardCore/OrchardCore.DisplayManagement.Liquid/LiquidViewTemplate.cs

Line 188 in 6911193

public static async Task<ViewContext> GetViewContextAsync(LiquidTemplateContext context)

Why does the log task need a httpcontext? is it because of liquid? if so, how do I get around this?

[weirdyang]

                using (ShellScope shellScope = await _shellHost.GetScopeAsync("Default"))
                {
                    await shellScope.UsingAsync(async scope =>
                    {
                        if (scope != null)
                        {
                            _httpContextAccessor.HttpContext = scope.ShellContext.CreateHttpContext();
                            IWorkflowManager manager = scope.ServiceProvider.GetRequiredService<IWorkflowManager>();
                            var messageData = new Dictionary<string, object>
                        {
                            { "value", cr.Message.Value is null ? "" : cr.Message.Value.ToString() },
                            { "key", cr.Message.Key is null ? "" : cr.Message.Key.ToString() },
                            { "topic", cr.Topic }
                        };
                            await manager
                                .TriggerEventAsync("EVENTNAME", messageData);
                        }
                    });
                }

I ended up doing something like this to add the httpcontext, will there be any issues?

[Piedone]

Sorry, I have no idea what this is about.

[weirdyang]

no worries thanks, managed to resolve it

[Piedone]

Awesome! Can you share your solution?

[weirdyang]

sure.

for context, what I'm doing is creating MQTT clients on startup and on update or creation of new profiles, and during the creation I am setting an event handler to call the following method:

        public async Task RunWorkflowAsync(MqttApplicationMessageReceivedEventArgs args, MqttProfile profile)
        {
            try
            {
                using (ShellScope shellScope = await _shellHost.GetScopeAsync("Default"))
                {
                    await shellScope.UsingAsync(async scope =>
                    {
                        if (scope != null)
                        {
                            _httpContextAccessor.HttpContext = scope.ShellContext.CreateHttpContext();
                            IWorkflowManager manager = scope.ServiceProvider.GetRequiredService<IWorkflowManager>();
                            var messageData = new Dictionary<string, object>
                        {
                            { "payload", args.ApplicationMessage is null ? "" : args.ApplicationMessage.ConvertPayloadToString() },
                            { "topic", string.IsNullOrWhiteSpace(args.ApplicationMessage?.Topic) ? "" : args.ApplicationMessage.Topic },
                            { "responseTopic", string.IsNullOrWhiteSpace(args.ApplicationMessage?.ResponseTopic) ? "" : args.ApplicationMessage.ResponseTopic },
                            { "profileId", profile.Id },
                            { "profileName", profile.ClientName }
                        };
                            await manager
                            .TriggerEventAsync(
                                MqttTopicEvent.EventName,
                                messageData,
                                isAlwaysCorrelated: true);
                        }
                    });
                }
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error handling event {event}", args);
            }
        }

what I noticed is that clients created on startup by my background service do not cause this issue, only clients created on update or creation of new profiles.

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            // get profiles from database and 
            // create clients
            await InitClients(stoppingToken);
            IsInitialised = true;
            await Task.Delay(Timeout.Infinite, stoppingToken);
        }

During update or creation of new profiles, I call a method on my background service to create/update new clients via event handlers

I tried setting the lifetime of the event handlers to singleton but it did not resolve the issue, so I realised it must be the parent calling method, which was the controller action lifetime that is causing this. So now I queue the update/create of clients and have the background service process it.

[Piedone]

Thank you for taking the time to share this!