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Is it possible that 2 azure functions can get triggered by one eventhub?

Is it possible that 2 azure functions can get triggered by one eventhub? One azure function will write its data to database1 and the other azure function writes its data to database2
[FunctionName("EventToDB1")]
public async System.Threading.Tasks.Task Run([EventHubTrigger("eventhub", Connection = "Debezium")]
EventData[] events, ILogger log)
{
{
[FunctionName("EventToDB2")]
public async System.Threading.Tasks.Task Run([EventHubTrigger("eventhub", Connection = "Debezium")]
EventData[] events, ILogger log)
{
{
answer on the possibility of having 2 azure functions get triggered by one eventhub

Yes that is possible by using different consumer groups. Because you specified the same connection to the Event Hub, being "Debezium", I Assume you want both funtions to process the same message. You have to create a new consumer group and specify the name using the ConsumerGroup property of the EventHubTrigger attribute (The default consumergroup is $Default):
public class EventToDB1
{
[FunctionName("EventToDB1")]
public async System.Threading.Tasks.Task Run(
[EventHubTrigger("eventhub",
Connection = "Debezium",
ConsumerGroup = "CG1")]
EventData[] events, ILogger log)
{
}
}
public class EventToDB2
{
[FunctionName("EventToDB2")]
public async System.Threading.Tasks.Task Run(
[EventHubTrigger("eventhub",
Connection = "Debezium",
ConsumerGroup = "CG2")]
EventData[] events, ILogger log)
{
}
}
Each consumer group receives the same messages from the Event Hub.

I do agree with #peter bons, you need to create two consumer groups for that and you can create two consumers by below process:
You can also use logic apps to work with event hubs.

Azure Function Event Hub Output Binding not working when deployed

I am using an Azure Function to get messages from a Rabbit MQ Broker to an Event Hub.
The function works perfect when I run it locally.
Here is the code of the function:
using System.Text;
using System.Dynamic;
using System.Threading.Tasks;
using CaseOnline.Azure.WebJobs.Extensions.Mqtt;
using CaseOnline.Azure.WebJobs.Extensions.Mqtt.Messaging;
using Microsoft.Azure.WebJobs;
using Newtonsoft.Json;
public static class Test
{
[FunctionName("EventHubOutput")]
public static async Task Run(
[MqttTrigger("topic/#")] IMqttMessage message,
[EventHub("eventhubname", Connection = "EventHubConnectionAppSetting")] IAsyncCollector<string> outputEvents,
ILogger log)
{
var body = message.GetMessage();
var bodyString = Encoding.UTF8.GetString(body);
dynamic obj = JsonConvert.DeserializeObject<ExpandoObject>(bodyString);
obj.Topic = message.Topic;
await outputEvents.AddAsync(JsonConvert.SerializeObject(obj));
}
}
When deployed and run in the Azure portal, I get the following error messages:
Microsoft.Azure.WebJobs.Host.FunctionInvocationException: Exception while executing function: EventHubOutput
---> System.InvalidOperationException: Error while handling parameter outputEvents after function returned:
---> System.Net.Sockets.SocketException (0xFFFDFFFF): Name or service not known
at (...)
Any idea what the problem might be?
Thank you.

You are using the bindings incorrectly. Check out RabbitMQ bindings for Azure Functions overview.
The following example shows a C# function that reads and logs the RabbitMQ message as a RabbitMQ Event:
[FunctionName("RabbitMQTriggerCSharp")]
public static void RabbitMQTrigger_BasicDeliverEventArgs(
[RabbitMQTrigger("queue", ConnectionStringSetting = "rabbitMQConnectionAppSetting")] BasicDeliverEventArgs args,
ILogger logger
)
{
logger.LogInformation($"C# RabbitMQ queue trigger function processed message: {Encoding.UTF8.GetString(args.Body)}");
}
The following example shows how to read the message as a POCO:
namespace Company.Function
{
public class TestClass
{
public string x { get; set; }
}
public class RabbitMQTriggerCSharp{
[FunctionName("RabbitMQTriggerCSharp")]
public static void RabbitMQTrigger_BasicDeliverEventArgs(
[RabbitMQTrigger("queue", ConnectionStringSetting = "rabbitMQConnectionAppSetting")] TestClass pocObj,
ILogger logger
)
{
logger.LogInformation($"C# RabbitMQ queue trigger function processed message: {pocObj}");
}
}
}
I recommend you to check out this complete guide to setup Rabbit MQ Trigger in Azure Functions: RabbitMQ trigger for Azure Functions overview

How to implement a triggerless .NET Core Console App as a continuous Azure WebJob?

All the code samples I've seen so far for Azure WebJobs rely on some kind of trigger (e.g. TimerTrigger or QueueTrigger).
I am looking specifically at WebJobs SDK 3.x, by the way.
So. For a triggerless WebJob (Windows Service-alike one), am I expected to use NoAutomaticTrigger and find a way to kickoff my "main" code manually?
Or should I resort to implementing and registering a class that implements the IHostedService interface?
So far that's the approach I'm taking but it feels more of a hack than a recommended way.
I have not even tried to deploy this code and only ran it on my local machine, so I am afraid that the publishing process will confirm my code is not suitable for Azure WebJobs in its current form.
EntryPoint.cs
This is how the application is being bootstrap when the process is starting.
using Microsoft.Azure.ServiceBus;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
namespace AbcCorp.Jobs
{
public static class Program
{
static async Task Main(string[] args)
{
var config = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
.AddJsonFile($"appsettings.{Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT")}.json", false)
.Build();
var hostBuilder = new HostBuilder()
.ConfigureWebJobs(builder => { builder.AddAzureStorageCoreServices(); })
.ConfigureServices(serviceCollection =>
{
ConfigureServices(serviceCollection, config);
serviceCollection.AddHostedService<ConsoleApplication>();
});
using (var host = hostBuilder.Build())
await host.RunAsync();
}
private static IServiceCollection ConfigureServices(IServiceCollection services, IConfigurationRoot configuration)
{
services.AddTransient<ConsoleApplication>();
// ... more DI registrations
return services;
}
}
}
ConsoleApplication.cs
This would normally be implemented as a function with a trigger.
The thing is, I want this code to only run once on the process startup.
It will start listening on the service bus events using the regular Microsoft.Azure.ServiceBus SDK package.
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Hosting;
using AbcCorp.Internal.Microsoft.Azure.ServiceBus;
using AbcCorp.Api.Messaging;
namespace AbcCorp.Jobs
{
public sealed class ConsoleApplication: IHostedService
{
private readonly IReceiver<SubmissionNotification> _messageReceiver;
private readonly MessageHandler _messageHandler;
public ConsoleApplication(IReceiver<SubmissionNotification> messageReceiver, MessageHandler messageHandler)
{
_messageReceiver = messageReceiver;
_messageHandler = messageHandler;
}
public Task StartAsync(CancellationToken cancellationToken)
{
_messageReceiver.StartListening(_messageHandler.HandleMessage, _messageHandler.HandleException);
return Task.Delay(Timeout.Infinite);
}
public Task StopAsync(CancellationToken cancellationToken)
{
_messageReceiver.Dispose();
return Task.CompletedTask;
}
}
}

So you want a console application to run in a WebJob and listen to messages. You don't really care about WebJob magic like triggers, it's just a place to run your console app. I've done the exact same thing before.
I found the IHostedService abstraction to be very helpful, but I didn't like their SDK. I found it bloated and hard to use. I didn't want to take a large dependency in order use a large array of special magic Azure stuff, when all I wanted to do was run a console application in a WebJob for now, and maybe move it elsewhere later.
So I ended just deleting that dependency, stealing the Shutdown code from the SDK and writing my own Service Host. The result is on my Github Repo azure-webjob-host. Feel free to use it or raid it for ideas. I don't know, maybe if I did it again I'd have another attempt at getting the SDK to work, but I present this is a bit of an alternative to the SDK.
Basically I wrote an IServiceHost not too different from yours (except that StartAsync exited when stuff started instead of just hanging). Then I wrote my own service host, which is basically just a loop:
await _service.StartAsync(cancellationToken);
while (!token.IsCancellationRequested){await Task.Delay(1000);}
await _service.StopAsync(default);
Then I stole the WebJobsShutdownWatcher code from their repo.
Then I created an IServiceHost that started my message handler. (I was using Rabbit, which has nothing to do with triggers or azure stuff)
public class MessagingService : IHostedService, IDisposable
{
public MessagingService(ConnectionSettings connectionSettings,
AppSubscriberSettings subscriberSettings,
MessageHandlerTypeMapping[] messageHandlerTypeMappings,
ILogger<MessagingService> logger)
{
....
}
public async Task StartAsync(CancellationToken cancellationToken)
{
cancellationToken.ThrowIfCancellationRequested();
await Task.WhenAll(subscribers.Value.Select(s => s.StartSubscriptionAsync()));
}
public async Task StopAsync(CancellationToken cancellationToken)
{
...
}
public void Dispose()
{
...
}
}
Then I put that all together into something like this:
IHostedService myService = new MyService();
using (var host = new ServiceHostBuilder().HostService(myService))
{
await host.RunAsync(default);
}

I have some workers attached to service bus topics and what we do is the following (ServiceBusClient is a custom Class that contains our Subscription Client):
public override Task StartAsync(CancellationToken cancellationToken)
{
_serviceBusClient.RegisterOnMessageHandlerAndReceiveMessages(MessageReceivedAsync);
_logger.LogDebug($"Started successfully the Import Client. Listening for messages...");
return base.StartAsync(cancellationToken);
}
public void RegisterOnMessageHandlerAndReceiveMessages(Func<Message, CancellationToken, Task> ProcessMessagesAsync)
{
// Configure the message handler options in terms of exception handling, number of concurrent messages to deliver, etc.
var messageHandlerOptions = new MessageHandlerOptions(ExceptionReceivedHandler)
{
// Maximum number of concurrent calls to the callback ProcessMessagesAsync(), set to 1 for simplicity.
// Set it according to how many messages the application wants to process in parallel.
MaxConcurrentCalls = 1,
// Indicates whether MessagePump should automatically complete the messages after returning from User Callback.
// False below indicates the Complete will be handled by the User Callback as in `ProcessMessagesAsync` below.
AutoComplete = false
};
// Register the function that processes messages.
SubscriptionClient.RegisterMessageHandler(ProcessMessagesAsync, messageHandlerOptions);
}
And then you can use DI to instantiate your service bus client and inject on the constructor of your Worker class.
Here i have the initialization of the singleton instance of my custom class Service Bus Client
services.AddSingleton<IServiceBusClient, ServiceBusClient>((p) =>
{
var diagnostics = p.GetService<EventHandling>();
var sbc = new ServiceBusClient(
programOptions.Endpoint,
programOptions.TopicName,
programOptions.Subscriber,
programOptions.SubscriberKey);
sbc.Exception += exception => diagnostics.HandleException(exception);
return sbc;
});
Then on this custom class, i initialize my subscription client
public ServiceBusClient(
string endpoint,
string topicName,
string subscriberName,
string subscriberKey, ReceiveMode mode = ReceiveMode.PeekLock)
{
var connBuilder = new ServiceBusConnectionStringBuilder(endpoint, topicName, subscriberName, subscriberKey);
var connectionString = connBuilder.GetNamespaceConnectionString();
ConnectionString = connectionString;
TopicName = topicName;
SubscriptionName = topicName;
SubscriptionClient = new SubscriptionClient(connectionString, topicName, subscriberName, mode);
}

You can check #george chen's answer from this post How to create service bus trigger webjob?
where instead of creating a receiver and registering a message handler, you can use the in built queue trigger and and write your message handler logic inside it.

Obtaining SignalR Hub without losing its clients from "other place in code"

I have app for one person that has to display data on webpage from external device connected via usb port
Before, I gave user button "Start listening" that sent http request to backend which started listening on port (and blocked app, but it was fine because it is supposed to be used by exactly 1 person at time) until it received not-error response (SerialDataReceivedEvent/SerialErrorReceivedEvent)
and SerialData was returned from that request and displayed on page
I have to rewrite this using SignalR, so I quickly came with naive solution like this:
public class DeviceReaderHub : Hub
{
private readonly IConfiguration _config;
// this is static because listening that port (SerialPort) has to stay open
private static DeviceReader_Helper _service;
public DeviceReaderHub(IConfiguration config)
{
_config = config;
if (_service == null)
{
_service = new DeviceReader_Helper();
_service.Open(_config["DeviceInfo:Port"]);
}
_service.DataReceived_Delegate = SendMessage;
_service.ErrorReceived_Delegate = SendErrorMessage;
}
public async Task SendMessage(string message)
{
await Clients.All.SendAsync("onRead", message);
}
public async Task SendErrorMessage(string message)
{
await Clients.All.SendAsync("onRead", $"error = {message}");
}
public async override Task OnConnectedAsync()
{
await Clients.All.SendAsync("onConnected");
await base.OnConnectedAsync();
}
}
but I received reality-check very quickly - I cannot do it like that because DeviceReaderHub is disposed.
Exception thrown: 'System.ObjectDisposedException' in Microsoft.AspNetCore.SignalR.Core.dll
I thought about obtaining new DeviceReaderHub hub whenever SerialDataReceivedEvent or SerialErrorReceivedEvent is being Invoked
but I have not idea how can I get instance of the hub without losing connected clients

SignalR hubs are transient objects, which means that a new hub instance is used for each method call on the hub from the client. According to this Microsoft Docs:
Don't store state in a property on the hub class. Every hub method call is executed on a new hub instance.
So you should not use the hub to do anything other than receiving and handling requests from the client. To send messages to the client outside of the hub, SignalR provides the HubContext<T> class which is available from Dependency Injection. For example:
public class DeviceReader_Helper {
private readonly IHubContext<DeviceReaderHub> _hubContext;
// you can obtain hubContext either from constructor DI, or service locator pattern with an IServiceProvider
public DeviceReader_Helper(IHubContext<DeviceReaderHub> hubContext) {
_hubContext = hubContext;
}
public async Task SendMessage(string message) {
await _hubContext.Clients.All.SendAsync("onRead", message);
}
}
For more information see this. As for your concern that
but I have not idea how can I get instance of the hub without losing connected clients
Clients can be connected without a hub instance. Hubs are only used to receive messages from the client, and are not necessary to keep a client connected to the server.

How to configure WebJob ServiceBusTrigger retry policy

Edit: I will accept Azure configuration related changes as an answer to this question.
I am attempting to setup a retry policy to prevent instantly retrying a message when a 3rd party service is temporarily unavailable.
Currently the job is retried immediately multiple times and fails each time due to the temporary outage of the 3rd party service.
How do I set a retry delay for these messages?
I have the following code for Main:
class Program
{
static void Main()
{
var config = new JobHostConfiguration();
if (config.IsDevelopment)
config.UseDevelopmentSettings();
config.UseCore();
config.UseServiceBus(new ServiceBusConfiguration()
{
ConnectionString = Configuration.GetAppSetting("Microsoft.ServiceBus.ConnectionString"),
MessageOptions = new OnMessageOptions()
{
}
});
var host = new JobHost(config);
LogManager.GetCurrentClassLogger().Information("F1.Birst.Automation web job starting.");
// The following code ensures that the WebJob will be running continuously
host.RunAndBlock();
}
}
I have an ErrorMonitor setup which properly logs errors:
public class ExceptionHandler
{
private static readonly ILogger Log = LogManager.GetCurrentClassLogger();
public void Handle([ErrorTrigger] TraceFilter message, TextWriter log)
{
foreach (var exception in message.GetEvents())
Log.Error(exception.Exception.InnerException, exception.Message);
}
}
And my message handler looks like this:
public class ChurchCodeChangedEventHandler : ChurchSpaceHandler
{
private static readonly ILogger Log = LogManager.GetCurrentClassLogger();
public void Handle([ServiceBusTrigger(nameof(ChurchCodeChangedEvent), "F1.Birst.Automation.ChurchCodeChangedEvent")] ChurchCodeChangedEvent message, TextWriter log)
{
Log.Information(LogTemplates.ChurchCodeChanged, message.ChurchId);
// snip
}
}

How do I set a retry delay for these messages?
Webjobs do not support the concept of delayed retries. You can only control a few things using ServiceBusConfiguration, but those are not retries looking at the source code.
You could use frameworks like NServiceBus or MassTransit to get delayed retries. There's an example of how to use NServiceBus with WebJobs and you can run it locally to see how delayed retries would work.