rabbitmq-consisten-hash-test

This project is used to show a potential error in the consistent-hash plugin of RabbitMQ. rabbitmq/rabbitmq-consistent-hash-exchange#32

Prerequisites

• dotnet sdk 3.1
• RabbitMQ 3.8.2 running with the rabbitmq_consistent_hash_exchange plugin

Setup RabbitMQ

• An exchange of type topic named exchange-in
• An exchange of type x-consistent-hash named exchange-consumer connected to the exchange-in exchage
• 5 queues named consumer.0 through consumer.4 with a binding to exchange-consumer an

Expected behavior

When sending a batch of 5000 messages each message should go to the same queue even after a restart of RabbitMQ.

Test

To execute the test, following the following steps multiple times:

1. execute dotnet run .
2. examine the number of messages in the consumer queueus and make note of the number per queue
3. on the rabbitmq instance call: rabbitmqctl stop_app
4. on the rabbitmq instance call: rabbitmqctl stop_app
5. examine the number of messages in the consumer queueus these should be all 0
6. repeat from step 1 until the values in step 2 are different for 1 or more queues

Initial run results

After a few runs

Problem

After a restart it can't be garanteed that messsages will be sent to the same queue.