getmempoolancestors - Bitcoin Cash

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

This method returns the in-mempool ancestors of a transaction: the unconfirmed transactions it depends on. Verbose mode returns full entry data for each ancestor.

Parameters

Parameter	Type	Required	Description
txid	string	Yes	The transaction id, which must be in the mempool
verbose	boolean	No	true for detailed objects, false for an array of txids. Default false

Request

cURL

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "getmempoolancestors",
    "params": ["10b54fd708ab2e5703979b4ba27ca0339882abc2062e77fbe51e625203a49642", false],
    "id": "getblock.io"
}'

bitcoinjs-lib

example.js

const axios = require('axios');
const { data } = await axios.post('https://go.getblock.io/<ACCESS-TOKEN>/', {
  jsonrpc: '2.0', method: 'getmempoolancestors',
  params: ['10b54fd708ab2e5703979b4ba27ca0339882abc2062e77fbe51e625203a49642', false], id: 'getblock.io'
});
console.log(data.result);

Request

example.py

import requests

response = requests.post(
    'https://go.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'getmempoolancestors',
        'params': ["10b54fd708ab2e5703979b4ba27ca0339882abc2062e77fbe51e625203a49642", false],
        'id': 'getblock.io'
    }
)

print(response.json()['result'])

Rust

example.rs

use reqwest::Client;
use serde_json::{json, Value};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new();

    let response = client
        .post("https://go.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&json!({
            "jsonrpc": "2.0",
            "method": "getmempoolancestors",
            "params": ["10b54fd708ab2e5703979b4ba27ca0339882abc2062e77fbe51e625203a49642", false],
            "id": "getblock.io"
        }))
        .send()
        .await?
        .json::<Value>()
        .await?;

    println!("Result: {}", response["result"]);
    Ok(())
}

Response

{
    "error": null,
    "id": "getblock.io",
    "result": [
        "780791bb2d5a8ccda4b5a707967a8e15b412814852c58c77299e85579bb65587"
    ]
}

Response Parameters

Parameter	Type	Description
error	null|object	Error object when the call fails, otherwise null
id	string	Request identifier matching the request
result	array|object	Array of ancestor txids, or detailed objects when verbose is true

Use Cases

• Dependency Resolution: Find unconfirmed parents that must confirm first

• CPFP Planning: Identify the ancestor chain when fee-bumping a transaction

• Package Relay: Assemble a transaction package with all its dependencies

• Spend Ordering: Order dependent transactions correctly before broadcast

Error Handling

Error Code	Message	Description
-8	Invalid parameter	txid is not a valid 64-character hex string
-5	Transaction not found	No transaction with the given id is available; a txindex may be required
-32603	Internal error	Node failed to read the transaction