Share base-services to keep packages lean would create disproportionate effort on hawkBit side

[laverman]

Motivation

Each service requires a set of base services (e.g. database, broker) to be available in the cluster. To keep resource consumption at a minimum it is desired to align the included base services, ending up with only one of a kind, e.g.

• MySQL as relation DB
• MongoDB as NoSQL DB
• Qpid as Message broker
• ...

Problem

Currently, there would be two message brokers (i.e. RabbitMQ for hawkBit, and Qpid for Hono) in the cluster. As discussed on the last Community call (13.01.) we wanted to aim for hawkBit to migrate to Qpid as well. However, this seems to be a bigger item than first anticipated, as ...

• the usage of RabbitMQ is not very well abstracted in hawkBit
• the migration from AMQP 0.9 to AMQP 1.0 would require more or less a rewrite of the DMF as it would make it incompatible with the current version

Hence, I'd like to stick with redundant messaging infrastructure for now.