The value 'Vendor\Xxx5\Model\Queue\Consumer::processMessage' is not accepted by the pattern '[a-zA-Z\\]+::[a-zA-Z]+'.

[weverson83]

The xml validator fail when you pass a class with numeric value in it's namespace.

Preconditions

Magento 2.2.2
magento/framework-message-queue

Steps to reproduce

1. Create etc/queue.xml file

<broker topic="xxxx" type="amqp" exchange="magento">
       <queue consumer="yyyy" name="zzzz" handler="Vendor\Xxx5\Model\Consumer::processMessage" consumerInstance="Magento\Framework\MessageQueue\Consumer"/>
    </broker>

2. Run bin/magento setup:upgrade

Actual result

The value 'Vendor\Xxx5\Model\Queue\Consumer::processMessage' is not accepted by the pattern '[a-zA-Z\]+::[a-zA-Z]+'.

Work arround

Created a virtualType for my class without a number in it's namespace

Solution

At vendor/magento/framework-message-queue/etc/queue_base.xsd

<xs:simpleType name="handlerType">
        <xs:annotation>
            <xs:documentation>
                @deprecated
                Handler is expected in a format "Vendor\Module\Api\ServiceName::methodName".
            </xs:documentation>
        </xs:annotation>
        <xs:restriction base="xs:string">
            <xs:pattern value="[a-zA-Z\\]+::[a-zA-Z]+" />
            <xs:minLength value="5" />
        </xs:restriction>
    </xs:simpleType>

Fix the pattern to accept numbers (Make sure it doesn't allow start with number)
[a-zA-Z]+[a-zA-Z0-9\\]+::[a-zA-Z0-9]+ should work

[engcom-backlog-nickolas]

@weverson83, thank you for your report. Please follow these guidelines for proper tracking of your issue. You can report Commerce-related issues in one of two ways:
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[domeglic]

@magento-engcom-team Can we reopen this issue because message queues are now in Open source, the issue still exists and was not fixed.
Magento: 2.3.3