Simple message bus contract

[brian-lc]

Overview

As a message bus consumer, so I can write a message that other services can read I want a contract that accepts my message for a topic. Also, so I can read messages on a topic I want a contract that will return messages on a topic.

Reference

• Mural
• Previous Issue

Questions

• How to structure the storage of messages?
• What is an appropriate return value for accepting messages?
• How are messages stored to the block?
• What is an appropriate cursor for messages?
• How are they ordered?
• How are topics represented?
• How are topics filtered?

Assumptions

• The contract will all receive messages, never send them.
• The contract will emit events that can be tracked by oracle-like objects

Acceptance

• It can accept a message to write to the bus
• it can return message body by message ID
• it can return a list of messages in a topic
• it can return a list of messages since a given message ID/cursor
• it emits an event when the message is stored

Interface Sketch

Always receives messages, never sends messages.
Interface to contract:
 - function sendMessage(string topic, string payload) returns bool?
 - function messagesSince(string topic, string cursor) returns messageList[]
 - function getMessage(string messageID) returns messageBody
 - function topicMessageCount(string topic) return numMessages