Initial codebase review for FireFly Transaction Manager

[peterbroadhurst]

This is a unit tested base set of functionality for the FireFly transaction manager for review.

Aligns with high level design outlined in hyperledger/firefly-ethconnect#149 (comment)

The architecture is summarized as follows:

• New FireFly Transaction Manager runtime
  • Operates as a microservice extension of the FireFly Core
  • Uses the operation resource within FireFly Core to store and update state
  • Runs as a singleton and is responsible for nonce assignment
  • Takes as much heavy lifting away from blockchain specific connectors as possible
• Lightweight FireFly Connector API (ffcapi)
  • Simple synchronous RPC operations that map to the most common operations supported across public blockchain technologies
  • Examples:
    • Find the next nonce for a given signing key
    • Serialize a transaction from a set of JSON inputs and an interface definition
    • Submit an un-signed transaction with a given gas price to the blockchain, via a signing wallet
    • Establish a new block listener
    • Poll for new blocks
    • Establish a new event log listener
    • Poll for new events
• Pluggable Policy Engine
  • Invoked to make decisions on transaction submission
  • Responsible for gas price calculation
  • Able to intervene and adjust the characteristics of signing/submission
  • OSS reference implementation provided with Gas Station REST API integration
• Confirmation Manager
  • Extracted from the Ethconnect codebase
  • Coupled to both transaction submission and event confirmation
  • Embeds an efficient block cache
• Event Streams - _not yet completed
  • Extracted from the Ethconnect codebase
  • Checkpoint restart based reliable at-least-once delivery of events
  • WebSockets interface upstream to FireFly Core

[awrichar]

Thanks for posting this - I've gone over the high level and it seems to match what we've discussed for this piece. I'm still going over the changes in more detail to see if I have any questions/concerns, but so far looks like a very good baseline.