Mirolim.EventStorage 1.1.0

There are two libraries

1. EventBus.RabbitMQ

EventBus.RabbitMQ is a messaging library designed to simplify the implementation of communication using RabbitMQ. It enables seamless publishing and receiving of events between microservices or other types of applications. The library is easy to set up and is compatible with .NET8 or recent frameworks. Additionally, it supports working with multiple virtual hosts in RabbitMQ.

With this library, you can easily implement the Inbox and outbox patterns in your application. It allows you to persist all incoming and outgoing event messages in the database. Currently, it supports storing event data only in a PostgreSQL database.

NuGet package

See the EventBus.RabbitMQ documentation for more information

2. EventStorage

EventStorage is a library designed to simplify the implementation of the Inbox and outbox patterns for handling multiple types of events in your application. It allows you to persist all incoming and outgoing event messages in the database. Currently, it supports storing event data only in a PostgreSQL database.

NuGet package

See the EventStorage documentation for more information

Getting started the EventStorage

EventStorage is a library designed to simplify the implementation of the Inbox and outbox patterns for handling multiple types of events in your application. It allows you to persist all incoming and outgoing event messages in the database. Currently, it supports storing event data only in a PostgreSQL database.

NuGet package

Setting up the library

Make sure you have installed and run PostgreSQL in your machine. After that, you need to install Mirolim.EventStorage NuGet package.

Install-Package Mirolim.EventStorage

Register the nuget package's necessary services to the services of DI in the Program.cs and pass the assemblies to find and load the events, publishers and receivers automatically:

builder.Services.AddEventStore(builder.Configuration,
    assemblies: [typeof(Program).Assembly]
    , options =>
    {
        options.Inbox.IsEnabled = true;
        options.Inbox.ConnectionString = "Connection string of the SQL database";
        //Other settings of the Inbox
        
        options.Outbox.IsEnabled = true;
        options.Outbox.ConnectionString = "Connection string of the SQL database";
        //Other settings of the Outbox
    });

Based on the configuration the tables will be automatically created while starting the server, if not exists.

Using the Outbox pattern while publishing event

Scenario 1: When user is deleted I need to notice the another service using the WebHook.<br/>

Start creating a structure of event to send. Your record must implement the ISendEvent interface. Example:

public record UserDeleted : ISendEvent
{
    public Guid EventId { get; } = Guid.NewGuid();
    
    public Guid UserId { get; init; }
    
    public string UserName { get; init; }
}

The EventId property is required, the other property can be added based on your business logic.<br/>

Since the library doesn't know about the actual sending of events, we need to create an event publisher specific to the type of event we want to publish. Add an event publisher by inheriting IWebHookEventPublisher and your UserDeleted event to manage a publishing event using the WebHook.

public class DeletedUserPublisher : IWebHookEventPublisher<UserDeleted>
{
    // private readonly IWebHookProvider _webHookProvider;
    //
    // public DeletedUserPublisher(IWebHookProvider webHookProvider)
    // {
    //     _webHookProvider = webHookProvider;
    // }

    public async Task<bool> Publish(UserDeleted @event, string eventPath)
    {
        //Add your logic
        return await Task.FromResult(false);
    }
}

The event provider support a few types: MessageBroker-for RabbitMQ message or any other message broker, Sms-for SMS message, WebHook- for WebHook call, Email for sending email, Unknown for other unknown type messages. Depend on the event provider, the event subscriber must implement the necessary publisher interface: IMessageBrokerEventPublisher, ISmsEventPublisher, IWebHookEventPublisher, IEmailEventPublisher and IUnknownEventPublisher- for Unknown provider type.

Now you can inject the IEventSenderManager interface from anywhere in your application, and use the Send method to publish your event.

public class UserController : ControllerBase
{
    private readonly IEventSenderManager _eventSenderManager;

    public UserController(IEventSenderManager eventSenderManager)
    {
        _eventSenderManager = eventSenderManager;
    }
    
    [HttpDelete("{id:guid}")]
    public IActionResult Delete(Guid id)
    {
        if (!Items.TryGetValue(id, out User item))
            return NotFound();

        var userDeleted = new UserDeleted { UserId = item.Id, UserName = item.Name };
        var webHookUrl = "https:example.com/api/users";
        var succussfullySent = _eventSenderManager.Send(userDeleted, EventProviderType.WebHook, webHookUrl);
        
        Items.Remove(id);
        return Ok(item);
    }
}

When we use the Send method of the IEventSenderManager to send an event, the event is first stored in the database. Based on our configuration (by default, after one second), the event will then be automatically execute the Publish method of created the DeletedUserPublisher event publisher.

If an event fails for any reason, the server will automatically retry publishing it, with delays based on the configuration you set in the Outbox section.

Scenario 2: When user is created I need to notice the another service using the RabbitMQ.<br/>

Start creating a structure of event to send. Your record must implement the ISendEvent interface. Example:

public record UserCreated : ISendEvent
{
    public Guid EventId { get; } = Guid.NewGuid();
    
    public Guid UserId { get; init; }
    
    public string UserName { get; init; }
    
    public int Age { get; init; }
}

Next, add an event publisher to manage a publishing event with the MessageBroker provider. Since the event storage functionality is designed as a separate library, it doesn't know about the actual sending of events. Therefore, we need to create single an event publisher to the specific provider, in our use case is for a MessageBroker.

public class MessageBrokerEventPublisher : IMessageBrokerEventPublisher
{
    // private readonly IEventPublisherManager _eventPublisher;
    
    // public MessageBrokerEventPublisher(IEventPublisherManager eventPublisher)
    // {
    //     _eventPublisher = eventPublisher;
    // }
    
    public async Task<bool> Publish(ISendEvent @event, string eventPath)
    {
        // _eventPublisher.Publish((IPublishEvent)@event);
        return await Task.FromResult(true);
    }
}

The MessageBrokerEventPublisher is serve for all kinds of events, those are sending to the MessageBroker provider. But if you want to create event publisher for the event type for being able to use properties of event without casting, you need to just create event publisher by using generic interface of necessary publisher. In our use case is IMessageBrokerEventPublisher<UserCreated>.

public class CreatedUserMessageBrokerEventPublisher : IMessageBrokerEventPublisher<UserCreated>
{
    // private readonly IEventPublisherManager _eventPublisher;
    //
    // public CreatedUserMessageBrokerEventPublisher(IEventPublisherManager eventPublisher)
    // {
    //     _eventPublisher = eventPublisher;
    // }
    
    public async Task<bool> Publish(UserCreated @event, string eventPath)
    {
        // _eventPublisher.Publish(@event);
        //Add you logic to publish an event to the RabbitMQ
        
        return await Task.FromResult(true);
    }
}

Since we want to publish our an event to the RabbitMQ, the event subscriber must implement the IMessageBrokerEventPublisher by passing the type of event (UserCreated), we want to publish. Your application is now ready to use this publisher. Inject the IEventSenderManager interface from anywhere in your application, and use the Send method to publish your UserCreated event.

public class UserController : ControllerBase
{
    private readonly IEventSenderManager _eventSenderManager;

    public UserController(IEventSenderManager eventSenderManager)
    {
        _eventSenderManager = eventSenderManager;
    }
    
    [HttpPost]
    public IActionResult Create([FromBody] User item)
    {
        Items.Add(item.Id, item);

        var userCreated = new UserCreated { UserId = item.Id, UserName = item.Name };
        var routingKey = "usser.created";
        var succussfullySent = _eventSenderManager.Send(userCreated, EventProviderType.MessageBroker, routingKey);
        
        return Ok(item);
    }
}

Is there any way to add some additional data to the event while sending and use that while publishing event?

Yes, there is a way to do that. For that, we need to just implement IHasAdditionalData interface to the event structure of our sending event:

public record UserCreated : ISendEvent, IHasAdditionalData
{
    public Guid EventId { get; }= Guid.NewGuid();
    
    public Guid UserId { get; init; } 
    
    public string UserName { get; init; }
    
    public Dictionary<string, string> AdditionalData { get; set; }
}

When we implement the implement IHasAdditionalData interface, it requires us to add collection property named AdditionalData. Now it is ready to use that:

var userCreated = new UserCreated { UserId = item.Id, UserName = item.Name };
userCreated.AdditionalData = new();
userCreated.AdditionalData.Add("login", "admin");
userCreated.AdditionalData.Add("password", "123");
var succussfullySent = _eventSenderManager.Send(userCreated, EventProviderType.MessageBroker, eventPath);

While publishing event, now you are able to read and use the added property from the your event:

public class CreatedUserMessageBrokerEventPublisher : IMessageBrokerEventPublisher<UserCreated>
{
    //Your logic
    
    public async Task<bool> Publish(UserCreated @event, string eventPath)
    {
        var login = @event.AdditionalData["login"];
        var password = @event.AdditionalData["password"];
        //Your logic
        _eventPublisher.Publish(@event);
        
        return await Task.FromResult(true);
    }
}

Using the Inbox pattern while receiving event

Start creating a structure of event to receive. Your record must implement the IReceiveEvent interface. Example:

public record UserCreated : IReceiveEvent
{
    public Guid EventId { get; init; }
    
    public Guid UserId { get; init; }
    
    public string UserName { get; init; }
    
    public int Age { get; init; }
}

Next, add an event receiver to manage a publishing RabbitMQ event.

public class UserCreatedReceiver : IRabbitMqEventReceiver<UserCreated>
{
    private readonly ILogger<UserCreatedReceiver> _logger;

    public UserCreatedReceiver(ILogger<UserCreatedReceiver> logger)
    {
        _logger = logger;
    }

    public async Task<bool> Receive(UserCreated @event)
    {
        _logger.LogInformation("EventId ({EventId}): {UserName} user is created with the {UserId} id", @event.EventId,
            @event.UserName, @event.UserId);
        //Add your logic in here
        
        return await Task.FromResult(true);
    }
}

Now the UserCreatedReceiver receiver is ready to receive the event. To make it work, from your logic which you receive the event from the RabbitMQ, you need to inject the IEventReceiverManager interface and puss the received event to the Received method.

UserCreated receivedEvent = new UserCreated
{
    //Get created you data from the Consumer of RabbitMQ.
};
try
{
    IEventReceiverManager eventReceiverManager = scope.ServiceProvider.GetService<IEventReceiverManager>();
    if (eventReceiverManager is not null)
    {
        var succussfullyReceived = eventReceiverManager.Received(receivedEvent, eventArgs.RoutingKey, EventProviderType.RabbitMq);
        if(succussfullyReceived){
            //If the event received twice, it will return false. You need to add your logic to manage this use case.
        }
    }else{
        //the IEventReceiverManager will not be injected if the Inbox pattern is not enabled. You need to add your logic to manage this use case.
    }
}
catch (Exception ex)
{
    //You need to add logic to handle some unexpected use cases.
}

That's all. As we mentioned in above, the event provider support a few types: MessageBroker-for RabbitMQ message or any other message broker, Sms-for SMS message, WebHook- for WebHook call, Email for sending email, Unknown for other unknown type messages. Depend on the event provider, the event receiver must implement the necessary receiver interface: IMessageBrokerEventReceiver, ISmsEventReceiver, IWebHookEventReceiver, IEmailEventReceiver and IUnknownEventReceiver- for Unknown provider type.

Options of Inbox and Outbox sections

The InboxAndOutbox is the main section for setting of the Outbox and Inbox functionalities. The Outbox and Inbox subsections offer numerous options.

"InboxAndOutbox": {
    "Inbox": {
      //Your inbox settings
    },
    "Outbox": {
      "IsEnabled": false,
      "TableName": "Outbox",
      "MaxConcurrency": 10,
      "TryCount": 5,
      "TryAfterMinutes": 20,
      "SecondsToDelayProcessEvents": 2,
      "DaysToCleanUpEvents": 30,
      "HoursToDelayCleanUpEvents": 2,
      "ConnectionString": "Connection string of the SQL database"
    }
  }

Description of options:

IsEnabled - Enables or disables the use of Inbox/Outbox for storing received/sent events. Default value is false. <br/> TableName - Specifies the table name used for storing received/sent events. Default value is "Inbox" for Inbox, "Outbox" for Outbox.<br/> MaxConcurrency - Sets the maximum number of concurrent tasks for executing received/publishing events. Default value is 10.<br/> TryCount - Defines the number of attempts before increasing the delay for the next retry. Default value is 10.<br/> TryAfterMinutes - Specifies the number of minutes to wait before retrying if an event fails. Default value is 5.<br/> SecondsToDelayProcessEvents - The delay in seconds before processing events. Default value is 1.<br/> DaysToCleanUpEvents - Number of days after which processed events are cleaned up. Cleanup only occurs if this value is 1 or higher. Default value is 0.<br/> HoursToDelayCleanUpEvents - Specifies the delay in hours before cleaning up processed events. Default value is 1.<br/> ConnectionString - The connection string for the PostgreSQL database used to store or read received/sent events.<br/>

All options of the Inbox and Outbox are optional, if we don't pass the value of them, it will use the default value of the option.