LastStoredRound

Storage Plain v216 → current

The most recent Drand round number stored on-chain.

Queried by: validatorsdevelopersanalytics

The Big Picture

Applications consuming randomness need to know what's available. This tells you the newest round - query Pulses(LastStoredRound) to get the freshest randomness. Also useful for monitoring: if this isn't incrementing, pulse submission has stalled.

Why This Matters

Always check LastStoredRound before using randomness. Don't assume a round exists - verify it's <= LastStoredRound. This is also your health metric: stale LastStoredRound means randomness infrastructure may be failing.

Example Scenario

Query LastStoredRound() returns 12345678. This is the newest round. Query Pulses(12345678) for the latest randomness. If LastStoredRound hasn't changed in hours, investigate - pulses should come every ~30 seconds.

Common Questions

Why might this stop incrementing?: Offchain worker failure, Drand beacon issues, or network problems. Check offchain worker logs and Drand beacon status (https://api.drand.sh/health).
Can rounds be skipped?: Yes - if a pulse isn't submitted, its round may be missing. The chain doesn't require sequential rounds, just valid signatures for whatever rounds are submitted.

Use Cases

Find the latest available randomness
Monitor Drand pulse submission health
Verify offchain workers are functioning
Build liveness dashboards for randomness infrastructure

Purpose & Usage

Purpose

Track the newest available randomness - queries should use this to find latest data.

Common Query Patterns

Query for the newest available round number
Combined with Pulses query to get latest randomness
Monitor to verify pulses are being submitted regularly

Part of: Distributed Randomness

Stored Value

u64

Value in RAO (÷10⁹ for TAO)

RAO -> TAO (/ 10^9)

Relationships

Modified By

write_pulse

Related Events

NewPulse

Code Examples

import { ApiPromise, WsProvider } from "@polkadot/api";
import { stringCamelCase } from "@polkadot/util";

const provider = new WsProvider("wss://entrypoint-finney.opentensor.ai:443");
const api = await ApiPromise.create({ provider });

// Query LastStoredRound storage (no keys - plain value)
const result = await api.query
  [stringCamelCase("Drand")]
  [stringCamelCase("LastStoredRound")]();
console.log("LastStoredRound:", result.toHuman());

Runtime Info

View Source

Pallet: Drand
Storage Kind: Plain
First Version: v216
Current Version: v393

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