How to rabbitmq-plugins enable rabbitmq_event_exchange in a different vhost not default vhost

[John Mattucci]

Just wondering how would I 'rabbitmq-plugins enable rabbitmq_event_exchange'  in a different vhost not default the vhost?


Thank you

[Michael Klishin]

Plugins are enabled node-wide.

On Tue, Oct 25, 2016 at 12:32 AM, John Mattucci <mattuc...@gmail.com> wrote:

Just wondering how would I 'rabbitmq-plugins enable rabbitmq_event_exchange'  in a different vhost not default the vhost?


Thank you

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MK

Staff Software Engineer, Pivotal/RabbitMQ

[John Mattucci]

But in https://github.com/rabbitmq/rabbitmq-event-exchange it states "It declares a topic exchange called 'amq.rabbitmq.event' in the default virtual host." And I wish to reference this exchange from a queue I created however it gives me the error "NOT_FOUND - no exchange 'amq.rabbitmq.event' in vhost '7857ed26-fccc-4ffc-bd95-1f20064ce451'" and I don't see amq.rabbitmq.event in the list of exchanges from the admin dashboard, however i see [E*] rabbitmq_event_exchange           3.6.3 when I do rabbitmq-plugins list.

On Tuesday, 25 October 2016 02:03:31 UTC-4, Michael Klishin wrote:

Plugins are enabled node-wide.

On Tue, Oct 25, 2016 at 12:32 AM, John Mattucci <mattuc...@gmail.com> wrote:

Just wondering how would I 'rabbitmq-plugins enable rabbitmq_event_exchange'  in a different vhost not default the vhost?


Thank you

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[Michael Klishin]

The event exchange plugin always uses default vhost — which can be configured for nodes that are blank

and need to initialise from scratch — by design.

In other words, you must connect to the default vhost if you intend to consume the events. There is no way to use

an arbitrary vhost or multiple vhosts.

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[Michael Klishin]

Perhaps some background explanation is warranted: plugins that publish data to an exchange (such as the event-exchange one)

need to decide what vhost to use because

1. We cannot not use any: resources such as exchanges in RabbitMQ always belong to a vhost.

2. Publishing to all vhosts makes no sense and will consume resources for no reason.

so plugin authors need to pick a vhost and in every case I've seen it's the default vhost [1] or

outright hardcode the "/" one (<<"/">>), even though it's not necessarily a great idea.

1. https://github.com/rabbitmq/rabbitmq-server/blob/stable/docs/rabbitmq.config.example#L166

[John Mattucci]

So in order to have this plugin exposed to a different vhost I would have to verify the plugin to check if its hardcoded or references the value in rabbitmq.config and then updated it accordingly?

[Michael Klishin]

You can configure the plugin to use any vhost you want but it can only be one vhost:
use `rabbitmq_event_exchange.vhost` [1].

1. https://github.com/rabbitmq/rabbitmq-event-exchange/blob/master/src/rabbit_exchange_type_event.erl#L93

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[John Mattucci]

Are there future plans to have the plugin accept multiple vhosts?

Thanks again for your time.

[Michael Klishin]

I don't think so. The stream of internal events is an inherently global thing that's only of interest to system operators.

[John Mattucci]

This leads me to ask, am I using the rabbit-event-exchange for its intended purpose, since in a PAAS environment where a service can be bound to a service such as rabbit and each space is assigned its own vhost

[Michael Klishin]

It is only meant to be used by operators. We don't know anything about your intent so can't comment further.

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[John Mattucci]

A queue is created which is bound to amq.rabbitmq.event and in turn based on the event messages i.e. queue is created, deleted etc. an action is undertaken