/// <summary>
/// Registers task and starts consuming messages
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="queueName"></param>
/// <param name="OnConsume"></param>
public void ConsumeTask <T>(string queueName, Func <T, TaskParameters, ClientActiveTasks, Task> OnConsume, Func <ClientActiveTasks, int> PostConsumeCleanup, ushort concurrency)
{
// Caution. The queue is also declard inside PublishTask above
_logger.LogInformation("Prefetch concurrency count {0}", concurrency);
lock (_channel)
{
_channel.QueueDeclare(queue: queueName,
durable: true,
exclusive: false,
autoDelete: false,
arguments: null);
// See https://www.rabbitmq.com/consumer-prefetch.html
// See https://stackoverflow.com/questions/59493540/what-is-prefetchsize-in-rabbitmq
_channel.BasicQos(prefetchSize: 0, prefetchCount: concurrency, global: false);
}
_logger.LogInformation(" [*] Waiting for messages, queueName - {0}", queueName);
var consumer = new EventingBasicConsumer(_channel);
consumer.Received += async(model, ea) =>
{
// This object exists so that we can wrap all OnConsumes with a try-finally here
// And during the finally block remove the task from the set of active tasks
// At this level of the code we don't have the specific task information
// Instead the specific task my register a task by calling register
ClientActiveTasks clientCleanup = new ClientActiveTasks();
var taskObject = CommonUtils.BytesToMessage <TaskObject <T> >(ea.Body);
_logger.LogInformation(" [x] {0} Received {1}", queueName, taskObject.ToString());
// TODO: Update JobStatus table here (started timestamp)
try
{
await OnConsume(taskObject.Data, taskObject.TaskParameters, clientCleanup);
}
catch (Exception e)
{
_logger.LogError(e, "Error occured in RabbitMQConnection {0} for message {1}", queueName, taskObject.ToString());
}
finally
{
PostConsumeCleanup(clientCleanup);
}
_logger.LogInformation(" [x] {0} Done {1}", queueName, taskObject.ToString());
// TODO Update JobStatus table here (including timestamp + result + exception if it occurred)
lock (_channel)
{
_channel.BasicAck(deliveryTag: ea.DeliveryTag, multiple: false);
}
};
lock (_channel)
{
_channel.BasicConsume(queue: queueName,
autoAck: false,
consumer: consumer);
}
}
public ClientActiveTasks(ClientActiveTasks source) : base(source)
{
}
