[DISPATCH-52] Distributed work-queue using dispatch to federate brokers.

• Type: Task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Component/s: Router Node
• Assignee: Alan Conway
• Reporter: Alan Conway
• Created: 14/May/14 14:32
• Updated: 12/Apr/19 16:00
• Resolved: 04/Nov/15 20:21

Description

Create a demonstration of a distributed work queue consisting of multiple brokers with the following requirements:

• Producers send to a single address, consumers subscribe to a single address.
• Each message is delivered to exactly one of the consumers (not fault tolerant/transactional)
• Consumers may connect and disconnect during the exercise without message loss.
• Messages are roughly balanced over consumers.
• All messages are delivered even if all but one consumer disconnects.
• In particular, messages do not get "stuck" on one broker because the consumer is only receiving from another brokers.

Goals:

1. Discover what changes to dispatch are needed to achieve this demonstration, enhance dispatch in a flexible way to support this and other possible "orchestration" tasks.

2. Once basic functionality is in place, explore further issues such as

• Performance: what overhead does dispatch add in throughput and latency vs. direct broker access?
• Scalability: can we scale total throughput linearly by adding brokers (and perhaps dispatch routers)?
  Are there limits/bottlenecks in dispatch that need to be addressed in order to scale?
• HA: If we use fault tolerant broker clusters can we get reliable at-least-once delivery? What changes to dispatch are needed to handle fail-over?

3. Build a similar demo of a distributed topic (TODO specify in more detail), to see if the extensions to dispatch are sufficient to support a different type of orchestration.

4. Push improvements into dispatch as they become mature/usable in a general context.