4-ledger.md

Ledger

• Configuration
  • Pool Selector Algorithm

Configuration

Ledgers to be used by the agent can be specified in the agent configuration using the indyLedgers config. Only indy ledgers are supported at the moment. The indyLedgers property is an array of objects with the following properties. Either genesisPath or genesisTransactions must be set, but not both:

• id*: The id (or name) of the ledger, also used as the pool name
• isProduction*: Whether the ledger is a production ledger. This is used by the pool selector algorithm to know which ledger to use for certain interactions (i.e. prefer production ledgers over non-production ledgers)
• genesisPath: The path to the genesis file to use for connecting to an Indy ledger.
• genesisTransactions: String of genesis transactions to use for connecting to an Indy ledger.

const agentConfig: InitConfig = {
  indyLedgers: [
    {
      id: 'sovrin-main',
      isProduction: true,
      genesisPath: './genesis/sovrin-main.txn',
    },
    {
      id: 'bcovrin-test',
      isProduction: false,
      genesisTransactions: 'XXXX',
    },
  ],
}

Pool Selector Algorithm

The pool selector algorithm automatically determines which pool (network/ledger) to use for a certain operation. For write operations, the first pool is always used. For read operations the process is a bit more complicated and mostly based on this google doc.

The order of the ledgers in the indyLedgers configuration object matters. The pool selection algorithm works as follows:

• When the DID is anchored on only one of the configured ledgers, use that ledger
• When the DID is anchored on multiple of the configured ledgers
  • Use the first ledger (order of indyLedgers) with a self certified DID
  • If none of the DIDs are self certified use the first production ledger (order of indyLedgers with isProduction: true)
  • If none of the DIDs are self certified or come from production ledgers, use the first non production ledger (order of indyLedgers with isProduction: false)
• When the DID is not anchored on any of the configured ledgers, a LedgerNotFoundError will be thrown.