Retry And Delivery Descriptors

This page describes descriptors responsible for reliability and resiliency.

These descriptors control:

• subscriber retries;
• publisher retries;
• publisher acknowledgements.

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RetryPolicyDescriptor

RetryPolicyDescriptor configures subscriber retry behavior.

Subscriber retry uses a RabbitMQ topology based on DLX, TTL and dead-letter routing.

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Retry Condition

A message enters the retry topology only when the subscriber handler sets:

args.Acknowledged = false;
args.Requeue = true;

If Requeue is false, the retry topology is not used.

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Runtime Topology

graph LR
    MainQueue["Main Queue"]
    Subscriber["Subscriber"]
    DlxExchange["DLX Exchange<br/>queue_dlx"]
    RetryQueue["Retry Queue<br/>queue_retry"]
    RetryExchange["Retry Exchange<br/>queue_retry"]

    MainQueue --> Subscriber
    Subscriber -->|"Acknowledged = false<br/>Requeue = true"| DlxExchange
    DlxExchange --> RetryQueue
    RetryQueue -->|"x-message-ttl expires"| RetryExchange
    RetryExchange --> MainQueue

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Generated Retry Objects

The provider creates retry infrastructure using the main queue name and suffixes.

Object	Suffix
DLX exchange	_dlx
Retry exchange	_retry
Retry queue	_retry

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Retry Queue Arguments

The retry queue uses these RabbitMQ arguments:

Argument	Purpose
x-message-ttl	Defines the retry delay.
x-dead-letter-exchange	Sends expired messages to the retry exchange.
x-queue-type	Defines the retry queue type.

x-queue-type is copied from the main queue when available.

Otherwise, the retry queue uses:

classic

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Properties

Property	Description
Enabled	Enables retry processing.
MaxRetry	Maximum retry attempts.
Delayed	Delay before the message is returned to the main queue.
Durable	Creates durable retry infrastructure.
AutoDelete	Controls retry object lifetime.

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Example

new RetryPolicyDescriptor
{
    Enabled = true,
    MaxRetry = 5,
    Delayed = TimeSpan.FromSeconds(10),
    Durable = true,
    AutoDelete = false
};

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PubRetryPolicyDescriptor

PubRetryPolicyDescriptor configures publisher retry behavior.

It is used when publish operations fail before the broker accepts the message.

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Example

new PubRetryPolicyDescriptor
{
    Enabled = true,
    MaxRetry = 5,
    Delayed = TimeSpan.FromSeconds(5)
};

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DeliveryConfirmation

DeliveryConfirmation configures RabbitMQ publisher acknowledgements.

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Purpose

Delivery confirmations allow a publisher to verify that RabbitMQ accepted a message.

sequenceDiagram
    participant Publisher
    participant RabbitMQ

    Publisher->>RabbitMQ: Publish
    RabbitMQ-->>Publisher: Ack / Nack

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Properties

Property	Description
Enabled	Enables publisher confirms.
WaitFor	Waits for confirmation before returning.
Timeout	Maximum wait duration.

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Example

new DeliveryConfirmation
{
    Enabled = true,
    WaitFor = true,
    Timeout = TimeSpan.FromSeconds(30)
};

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Retry vs Delivery Confirmation

Feature	Purpose
RetryPolicyDescriptor	Retry subscriber message processing through DLX/TTL topology.
PubRetryPolicyDescriptor	Retry publishing operations.
DeliveryConfirmation	Verify broker acceptance.

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Recommendations

Use:

• RetryPolicyDescriptor for transient consumer failures;
• PubRetryPolicyDescriptor for transient publishing failures;
• DeliveryConfirmation when message loss is unacceptable.