CrestApps.Queues 1.0.1

Queues

This module offers essential services for queuing elements and processing them in the background. It proves particularly useful when there is a need to queue tasks such as notifications or emails for background processing.

Since this module focuses solely on providing core services, it is marked with the EnabledByDependencyOnly flag, making it available on demand.

To utilize this module, you can create an OrchardCore module and add a dependency on CrestApps.Queues feature. Additionally, to handle your queue items, you need to implement the IQueueElementProcessor, which is responsible for processing the queued elements.

For queuing elements, utilize the IQueueStore interface.

Example of implementing an Email Queue Processor

In this example, we employ a retry logic of 5 attempts in this instance to enable the processing of the queue element before considering it abandoned.

public class EmailQueueProcessor : IQueueElementProcessor
{
    /// <summary>
    /// Sets the max attempts to send the email before abandon the element.
    /// </summary>
    private const int _maxAttempts = 5;

    private readonly ISmtpService _smtpService;

    private IEnumerable<User> _users;

    public EmailQueueProcessor(ISmtpService smtpService)
    {
        _smtpService = smtpService;
    }

    public bool CanHandle(string queueName)
    {
        return queueName == "Email";
    }

    public Task<bool> IsProcessableAsync(QueueElement element)
    {
        return Task.FromResult(element.FailedCounter < _maxAttempts);
    }

    public async Task ProcessAsync(QueueElementProcessingContext context)
    {
        foreach (var item in context.Elements)
        {
            var message = item.As<MailMessage>();

            if(message == null)
            {
                // No message was found on the queue element.
                item.IsRemovable = true;

                continue;
            }

            var result = await _smtpService.SendAsync(message);

            item.IsProcessed = result.Succeeded;
        }
    }
}

Example of creating Email Queue elements using a Content Type Handler.

In this particular scenario, we make the assumption that there exists a content type called ContactFormEntry which is completed by a site visitor. Our objective is to enqueue an email for sending it to the site owner.

public class ContactFormContentType : ContentHandlerBase
{
    private const string _contentType = "ContactFormEntry";

    private readonly IQueueStore _queueStore;

    public ContactFormContentType(IQueueStore queueStore)
    {
        _queueStore = queueStore;
    }

    public override Task PublishedAsync(PublishContentContext context)
    {
        if(context.PublishingItem.ContentType != _contentType)
        {
            return Task.CompletedTask;
        }

        return AddOrUpdateNotificationQueueAsync(context.PublishingItem);
    }

    public override Task UnpublishedAsync(PublishContentContext context)
    {
        if (context.PublishingItem.ContentType != _contentType)
        {
            return Task.CompletedTask;
        }

        return RemoveNotificationQueueAsync(context.PublishingItem);
    }

    public override Task RemovedAsync(RemoveContentContext context)
    {
        if (context.ContentItem.ContentType != _contentType)
        {
            return Task.CompletedTask;
        }

        return RemoveNotificationQueueAsync(context.ContentItem);
    }

    private async Task AddOrUpdateNotificationQueueAsync(ContentItem contentItem)
    {
        var queueItems = await _queueStore.GetCorrelationAsync(contentItem.ContentItemId);

        // Get event date and add minuts to it.
        var queueItem = queueItems.FirstOrDefault(x => x.QueueName == "Email")
            ?? new QueueElement()
        {
            CorrelationId = contentItem.ContentItemId,
            QueueName = "Email",
        };

        // The Mail info will come from the contact form entry or other sources.
        var message = new MailMessage()
        {
            Subject = contentItem.Content.ContactFormEntry.Subject.Text,
            Body = contentItem.Content.ContactFormEntry.Message.Text,
            To = "owner@example.com",
        };

        queueItem.Put(message);

        await _queueStore.SaveAsync(queueItem);

        await _queueStore.SaveChangesAsync();
    }

    private async Task RemoveNotificationQueueAsync(ContentItem contentItem)
    {
        var queueItems = await _queueStore.GetCorrelationAsync(contentItem.ContentItemId);

        foreach (var queueItem in queueItems)
        {
            if (queueItem.QueueName != "Email")
            {
                continue;
            }

            await _queueStore.DeleteAsync(queueItem);
        }

        await _queueStore.SaveChangesAsync();
    }
}