Support custom routing keys per message

[creyke]

Please can you make it possible to define the routing key per-message. This is a common requirement of RabbitMQ message producers where specific properties of the message are used to determine how the key can be filtered.

A proposal could be to change the generic argument of RabbitMQAsyncCollector from byte[] to a RabbitMQMessage which exposes both a byte[] Body property, and a string RoutingKey.

If the latter is left null, then the routing key would be defaulted to the QueueName when added to the batch, else the message specific routing key would be used.

[Beungoud]

Hello,
To go further on this idea, we also need a way to push messages not only to "queues" but also to rabbitMQ "exchange".
Pushing only to queues seems a limitation on the usage of routing keys.

[creyke]

I'm very willing to implement this and open a PR - I just need guidance from the team as to how the meta data of the message should be provided (currently there's just a byte[], so assume there would need to be a parent object of that).

[yojagad]

I think the way to go about about this would be, instead of introducing a custom wrapper like in the PR here #77, actually add support for IAsyncCollector<BasicDeliverEventArgs> along with introducing the respective converters for

• Converting from string to BasicDeliverEventArgs (replacing the existing converter from string to byte[])
• Converting from Poco to BasicDeliverEventArgs (replacing the existing converter from Poco to byte[])
• Converting from byte[] to BasicDeliverEventArgs (this would be a new converter to prevent breaking changes)

[yojagad]

Other points from further discussion

• As publish method does not take BasicDeliverEventArgs directly, we therefore do not have a mechanism to expose this as part of output binding. Reference line https://github.com/Azure/azure-functions-rabbitmq-extension/blob/dev/src/Bindings/RabbitMQAsyncCollector.cs#L33

We will revisit this feature ask when the underlying SDK supports publishing to queue with BasicDeliverEventArgs as input.

[cachai2]

Blocked. There is no current API to leverage