After upgrading to RabbitMQ 4.0.8, it is not possible to retrieve messages.

[flyingcrp]

First of all, I apologize for asking this question. While maintaining an old RabbitMQ instance with this plugin, I tried to upgrade it; after the upgrade, I can no longer receive delayed messages.

I made the following attempts:

1. After upgrading from RabbitMQ 3.x to the latest version and enabling Khepri, I followed the documentation to enable and disable the plugin and restarted the instance (a standalone service, not a cluster).
2. I used the normal topic mode, and everything was functioning normally.
3. When I used the plugin to prepare to send delayed messages, the sending was normal (both the code and the web UI were functioning correctly); however, the consumer could not receive the messages.

the service configuration and plugin information are as follows.

Below is the information about the exchange and queues in the webui.

Exchange:

Queue:

When I publish a message from the webui, I received the following reminder.

I am very confused about this, please let me know if I missed something. Thank you very much.

[michaelklishin]

@flyingcrp the answer is starting at you from the README section.

If you disable this plugin, it will delete the Mnesia table where it stores all messages. They are not replicated, which is also documented in a section called Limitations.

Finally, the "message published but not routed" message is explined in the same section on limitations: this exchange type cannot support publishing with the mandatory flag set, and that's exactly what the management UI form does.

[flyingcrp]

I'm sorry to ask again. I carefully read the link you provided (thank you again for your patient response) and checked the corresponding settings, but the consumers still haven't received any delayed messages;

I publish messages through a program (nodejs, amqp-connection-manager library), and set mandatory to true when publishing;

My question is: there is a correct binding relationship between the exchange and the queue (which can be seen from the web UI), the routing key of the queue matches the published routing key (published: delay.msg, consumer: *.msg); the consumer still cannot receive the delayed message?

thanks

[flyingcrp]

I seem to have found the problem.

I tried the following operations:

• Upgraded directly from 3.x to the latest 4.x, passed testing
• Upgraded directly from 3.x to the latest 4.x, enabled all Feature Flags (rabbitmq_4.0.0, rabbit_exchange_type_local_random), passed
• Based on the previous step, enabled khepri_db, and restarted the node (docker restart rabbitmq-server, from the release notes), the delayed messages exhibited the previously discussed situation (binding relationships correct, routing keys correct) but the consumer could not receive the delayed messages.

It seems that after upgrading from 3.x to 4.x and enabling khepri_db, delayed messages are not working as expected.

I can only give up on enabling khepri_db for now, but according to the official description, it will only use khepri_db in the future, which makes me very worried about how I will upgrade in the future. I can no longer perform deeper debugging, and I hope to get your help. Thank you very much.

[michaelklishin]

@flyingcrp from the 4.0.7 release notes:

This plugin is 4.0 compatible with the following limitations:

• If the cluster uses Mnesia for schema store, it works exactly as it did against RabbitMQ 3.13.x
• If the cluster uses Khepri and the plugin is enabled after Khepri, it will start Mnesia, set up a node-local Mnesia replica and schema, and works as in scenario 1
• Important: if the cluster uses Mnesia, then the plugin is enabled, and then Khepri is enabled, the plugin must be disabled and re-enabled, or the node must be restarted. Then it will start Mnesia and works as in scenario 2

[michaelklishin]

@flyingcrp you ignore every single warning in the docs and release notes, publish specifically using an explicitly unsupported feature (mandatory publishing), and in the end decide to forego an incredibly useful and recommended feature (Khepri) instead of doing what the release notes tell you to do.

I'm sorry, our small team cannot afford to spend time on such borderline trolling questions. Everything you have run into has been documented, everything we recommend you ignore. You will have to seek RabbitMQ help elsewhere.