RabbitMQAdvancedPatterns (.NET 10)

A minimal set of console apps demonstrating common RabbitMQ messaging patterns using RabbitMQ.Client (v7.x) and RabbitMQ running locally in Docker.

Prerequisites

• .NET SDK 10.0
• Docker Desktop (or Docker Engine)

Start RabbitMQ locally (Docker)

docker run --rm -it -p 5672:5672 -p 15672:15672 rabbitmq:3-management

• AMQP: localhost:5672
• Management UI: http://localhost:15672 (user/pass: guest / guest)

Build everything

From the repository root:

dotnet build .\RabbitMQAdvancedPatterns.slnx

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1) Work Queue Pattern (+ Dead Letter Queue)

Projects

• Producer: RabbitMQAdvancedPatterns\WorkQueueProducer
• Consumer: RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\WorkQueueConsumer
• DLQ consumer: RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\DeadLetterConsumer

Run the work-queue consumer

Terminal A:

dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\WorkQueueConsumer\WorkQueueConsumer.csproj

Send tasks

Terminal B:

dotnet run --project .\RabbitMQAdvancedPatterns\WorkQueueProducer\WorkQueueProducer.csproj -- "task one..."
dotnet run --project .\RabbitMQAdvancedPatterns\WorkQueueProducer\WorkQueueProducer.csproj -- "task two."

Notes:

• Messages are sent to a durable queue named task_queue.
• The consumer uses manual acknowledgements (BasicAckAsync).
• Dots (.) simulate work time (1 second per dot).

Demonstrate DLQ (Dead Letter Queue)

Start the DLQ consumer:

Terminal C:

dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\DeadLetterConsumer\DeadLetterConsumer.csproj

Send a failing task (contains the word fail):

Terminal B:

dotnet run --project .\RabbitMQAdvancedPatterns\WorkQueueProducer\WorkQueueProducer.csproj -- "fail this task"

Expected:

• WorkQueueConsumer rejects the message (BasicRejectAsync(requeue: false))
• RabbitMQ routes it to dead_letter_queue via dlx_exchange
• DeadLetterConsumer prints the dead-lettered message

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2) Publish / Subscribe Pattern (Fanout Exchange)

Projects

• Publisher: RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\PubSubPublisher
• Subscriber: RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\PubSubSubscriber

Run one or more subscribers

Terminal A (and/or B):

dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\PubSubSubscriber\PubSubSubscriber.csproj

Publish a broadcast message

Terminal C:

dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\PubSubPublisher\PubSubPublisher.csproj -- "hello everyone"

Expected:

• Publisher sends to fanout exchange logs_exchange
• Every subscriber receives and prints the broadcast

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3) Routing Pattern (Direct Exchange)

Projects

• Publisher: RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\DirectPublisher
• Subscriber: RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\DirectSubscriber

Run a subscriber for specific severities

Terminal A:

dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\DirectSubscriber\DirectSubscriber.csproj -- warning error

Publish with a routing key (severity)

Terminal B:

dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\DirectPublisher\DirectPublisher.csproj -- info "this will NOT be received"
dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\DirectPublisher\DirectPublisher.csproj -- error "this WILL be received"

Expected:

• Messages are published to direct_logs_exchange
• Subscriber receives only the routing keys it bound to (e.g., warning, error)

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4) Topic Exchange Pattern

Projects

• Publisher: RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\TopicPublisher
• Subscriber: RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\TopicSubscriber

Run a topic subscriber with binding patterns

Terminal A:

dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\TopicSubscriber\TopicSubscriber.csproj -- "kern.*" "*.critical"

Publish topic messages

Terminal B:

dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\TopicPublisher\TopicPublisher.csproj -- "kern.critical" "kernel panic"
dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\TopicPublisher\TopicPublisher.csproj -- "app.info" "startup ok"

Expected:

• Messages are published to topic_logs_exchange
• Subscriber receives only messages whose routing keys match its patterns

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5) Retry Pattern (Delay + Retry + Final DLQ)

This retry demo is implemented as separate projects so it does not change the Work Queue / DLQ demo.

Projects

• Producer: RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\RetryProducer
• Consumer: RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\RetryConsumer

Broker entities used by this demo

• Task queue: retry_demo_task_queue
• Retry delay queue (TTL): retry_demo_retry_queue (defaults to 5s delay)
• DLX: retry_demo_dlx_exchange
• DLQ: retry_demo_dead_letter_queue

Run the retry consumer

Terminal A:

dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\RetryConsumer\RetryConsumer.csproj

Send a message that triggers retries

Terminal B:

dotnet run --project .\RabbitMQAdvancedPatterns\RabbitMQAdvancedPatterns\RetryProducer\RetryProducer.csproj -- "fail please"

Expected:

• The consumer schedules retries by republishing to the TTL-based retry_demo_retry_queue
• After the delay, RabbitMQ dead-letters the message back to retry_demo_task_queue
• After MaxRetries is exceeded, the consumer rejects it to the demo DLQ (retry_demo_dead_letter_queue)

You can also watch queue depths in the Management UI: http://localhost:15672.