consensus_subscribe - Tempo

Example code for the consensus_subscribe JSON-RPC method. Complete guide on how to use consensus_subscribe JSON-RPC in GetBlock Web3 documentation.

WebSocket subscription to consensus events. Emits events when blocks are notarized, finalized, or views are nullified. Available on validator nodes over WebSocket only.

VALIDATOR-NODE-ONLY METHOD. This method is part of the consensus_* namespace and is only available on Tempo validator nodes. It is not available on shared RPC infrastructure such as GetBlock's standard shared endpoints. Calling this method against a non-validator node returns -32601 Method not found. If you need access, contact GetBlock for dedicated validator node access.

Parameters

None

Request Example

# WebSocket-only method. Use wscat (or similar) to connect first:
wscat -c 'wss://go.getblock.io/<ACCESS-TOKEN>/'

# Then send:
{"jsonrpc": "2.0", "method": "consensus_subscribe", "params": [], "id": "getblock.io"}

import WebSocket from 'ws';

const ws = new WebSocket('wss://go.getblock.io/<ACCESS-TOKEN>/');

ws.on('open', () => {
    ws.send(JSON.stringify({
    "jsonrpc": "2.0",
    "method": "consensus_subscribe",
    "params": [],
    "id": "getblock.io"
}));
});

ws.on('message', (data) => {
    console.log(JSON.parse(data.toString()));
});

import asyncio
import json
import websockets

async def main():
    async with websockets.connect('wss://go.getblock.io/<ACCESS-TOKEN>/') as ws:
        await ws.send(json.dumps({
    "jsonrpc": "2.0",
    "method": "consensus_subscribe",
    "params": [],
    "id": "getblock.io"
}))
        async for message in ws:
            print(json.loads(message))

asyncio.run(main())

use tokio_tungstenite::connect_async;
use tokio_tungstenite::tungstenite::Message;
use serde_json::json;
use futures_util::{SinkExt, StreamExt};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let (mut ws_stream, _) = connect_async("wss://go.getblock.io/<ACCESS-TOKEN>/").await?;

    let payload = json!({
        "jsonrpc": "2.0",
        "method": "consensus_subscribe",
        "params": [],
        "id": "getblock.io"
});
    ws_stream.send(Message::Text(payload.to_string())).await?;

    while let Some(msg) = ws_stream.next().await {
        println!("{:?}", msg?);
    }
    Ok(())
}

Response Example

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0x9cef478923ff08bf67fde6c64013158d"
}

Response Parameters

Field

Type

Description

result

string

Subscription ID. Streamed events arrive as separate WebSocket messages with type ∈ notarized | finalized | nullified

(event) type

string

One of notarized, finalized, nullified

(event) epoch

integer

Consensus epoch

(event) view

integer

Consensus view

(event) digest

string

Block digest (omitted for nullified)

(event) certificate

string

BLS certificate (omitted for nullified)

(event) block

object

Full Tempo block (omitted for nullified)

(event) seen

integer

Unix timestamp in milliseconds when the node observed the event

Use Cases

Validator-side real-time consensus monitoring
Bridge relayers that act immediately on finalization
Low-latency notarized-block feeds for advanced UX

Error Handling

Status Code

Error Message

Cause

403

Forbidden

Missing or invalid <ACCESS-TOKEN>

-32602

Invalid params

Request parameters are missing or malformed

-32601

Method not found

Method does not exist or is not enabled on this node

429

Too Many Requests

Rate limit exceeded for your plan

-32601

Method not found

This is a validator-only WebSocket method — not exposed on shared infrastructure

-32600

Invalid Request

Called over HTTP instead of WebSocket

SDK Integration

import WebSocket from 'ws';

const ws = new WebSocket('wss://go.getblock.io/<ACCESS-TOKEN>/');

ws.on('open', () => {
    ws.send(JSON.stringify({
        jsonrpc: '2.0',
        id: 'getblock.io',
        method: 'consensus_subscribe',
        params: []
    }));
});

ws.on('message', (data) => console.log(JSON.parse(data.toString())));

import asyncio, json, websockets

async def main():
    async with websockets.connect('wss://go.getblock.io/<ACCESS-TOKEN>/') as ws:
        await ws.send(json.dumps({
            'jsonrpc': '2.0', 'id': 'getblock.io',
            'method': 'consensus_subscribe', 'params': []
        }))
        async for msg in ws:
            print(json.loads(msg))

asyncio.run(main())

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