Minimum Viable Message Bus 🚌

[barlock]

Overview

As an engineer connecting services, I want an always-on, tamper-resistant message bus to pass messages between services so that I can coordinate my services.

Reference

• Epic - MB for Stratego
• Atomic Crosschain Transactions (Pantheon)
• chain.link
• General Message Bus Pattern

Questions

• What patterns exist in other MQ, MB systems?
• What steps should be put in place to prevent deadlocking?
  • Is it all on the client? Does the MB need to expose features to allow clients to prevent deadlocking?
  • Should a "time-lock" mechanism be put in place? See Atomic Crosschain Transactions. "Message slots" per topic for concurrency?

Assumptions

• Optimize for keeping gas low

Acceptance

• A smart contract to be used as a MB, it should:
  • accept a message and provide guarantees that once the calling process get's a successful return that the message is guaranteed (to some degree) to be durable.
  • Provide some way for services to request messages since a cursor (timestamp, vector, clock, hash chain, etc..)
  • Provide some scheme for additional metadata on the messages that could be read (optionally) by services and used for filtering. (topics, senders, etc.)
  • Emit events allowing services to process in real time
  • Allow for deadlock prevention (See questions)

[brian-lc]