Utility Session Protocol

Session Protocol

• Interface
• Session Creation Flow

*WIP: Run TODO*SEARCH=utility/session* make todo*search to identify all the WIP related to session generation.*

Interface

Pocket satisfies the V1 Utility Specification's Session Protocol by implementing the following function from the Utility Module Interface and returning a Session Protobuf:

GetSession(appAddr string, sessionHeight int64, relayChain string, geoZone string) (*coreTypes.Session, error)

Session Creation Flow

The following is a simplification of the session creation flow for illustrative purposes only.

See session.go and session_test.go for the full implementation.

1. Create a session object from the seed data
2. Create a key concatenating and hashing the seed data
   • sessionId = Hash(sessionHeight + blockHash + geoZone + relayChain + appPublicKey)
3. Get an ordered list of the public keys of servicers and fishermen who are:
   • actively staked
   • staked within geo-zone
   • staked for relay-chain
4. Use a pseudo-random selection algorithm to retrieve the fishermen and servicers for for the sessionId

sequenceDiagram
    %% The `Querier` is anyone (app or not) that asks to retrieve session metadata
    actor Q AS Querier

    participant S AS Session Hydrator
    participant WS AS WorldState

    Q->>WS: Who are the servicers and fisherman ([app], [relayChain], [geoZone])
    WS->>S: seedData = (height, blockHash, [geoZone], [relayChain], [app])

    S->>S: sessionId = hash(concat(seedData))
    WS->>S: servicerList = Ordered list of public keys of applicable servicers

    S->>S: sessionServicers = pseudorandomSelect(sessionKey, servicerList, max)
    WS->>S: fishList = Ordered list of public keys of applicable fishermen

    S->>S: sessionFishermen = pseudorandomSelect(sessionKey, fishList, max)
    S->>Q: SessionServicers, sessionFishermen

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