Document common patterns to use in Apps

[mattyg]

Common patterns used in app development

Must include:

• code examples
• practical, terse explanation
• gotchas

Possible topics include:

• Lobby
  • gaining access to privileged DHTs
  • getting directory of DNA clones
  • mediated access to other DHTs via call_remote
• Blockchain binding
• File chunking
• DNA composability
  • One DHT per file/channel
  • Throwaway DHT
  • Per-role DNAs (combine with Lobby for mediated access)
• Various CRUD patterns
  • See https://github.com/mjbrisebois/blog/blob/master/drafts/holochain-architectural-pattern-vectors.md
  • Canonical updates
    • Simple resolution strategy (e.g., LWW)
    • Branch pointer (requires consensus protocol)
  • 'latest update' link
  • Update trees
• Communications
  • Asynchronous private messaging
  • Mailbox
• Access control / privileges / privacy / secrecy
  • Benevolent dictator
  • Progenitor
  • Capability delegation
  • Memproofs for DHT read / peer connection privileges
    • Token gating
    • Group password (better handled by network seed TBH)
    • Certificate chains
    • Lobby can be used to distribute memp
  • DHT writes
    • Only author can edit
    • Read-only public DHT with memproof for write privileges (necessary for Holo resilience nodes to work)
  • Encrypted DHT data
    • key rotation for forward secrecy
      • double ratchet
      • manual rotation
  • Private data and call_remote
  • Homomorphic encryption
  • ZKP
  • Negotiation of shared secret, e.g., dice roll
    • SMPC (e.g., EcDSA)
    • just sharing the darn secret
  • Shared secrets, public disclosure/auditing
• Validation
  • Inductive validation
• Remote signals
  • Heartbeat / presence indicators
    • Online-ish-ness -- dealing with ambiguous definition of 'online' in P2P context
    • swarm connectivity -- how connected am I to the people I'm doing work with?
    • beacon or sentinel -- am I connected to 'the internet' (or at least the portion that I expected to see)?
  • Anchor pub/sub
  • Publish frontrunning -- sending out a signal in post_commit to let listeners know that a DHT entry should exist there eventually
  • Real-time collaboration
    • Syn v1 (scribe that collects CRDTs from collaborators, periodically commits change sets)
    • Syn v2 (no scribe needed; don't know how this'll work yet)
    • Branching revisions
• Consensus protocols
  • Countersigning-based
    • Single notary
    • Notary pool (m-of-n optional witnesses)
  • Hardened metadata (will be supported by Holochain eventually; curious if it could be implemented as an app-level pattern)
  • Blockchain binding