Extending a deployed contract’s TTL using code

When a smart contract is deployed on the Stellar network, its WebAssembly (Wasm) code has a Time To Live (TTL) that determines how long it remains accessible.

The TTL is the number of ledgers between the current ledger and the final ledger for which the contract data can still be accessed. If the TTL expires, the contract's code becomes archived and inaccessible. To prevent this, you need to periodically extend the TTL of the contract's Wasm code.

This guide will show you how to extend the TTL of a deployed contract's Wasm code using JavaScript.

Prerequisites

• Stellar SDK: npm install @stellar/stellar-sdk
• A Stellar RPC endpoint (e.g., https://soroban-testnet.stellar.org)
• Basic knowledge of Stellar SDK

Process overview

• Get the contract's footprint,
• Set a reasonable resource fee (perhaps start at 10,000 stroops as this is a costly operation),
• Set Soroban data as read-only,
• Set the desired ledger TTL to expire the contract,
• Create an operation StellarSdk.Operation.extendFootprintTtl,
• Note that a resource fee and base fee are both charged in this operation.

JavaScript code

The code below uses Nodejs environment but same concept can also be applied in the browser using Freighter wallet or using any other Stellar SDK.

import * as StellarSdk from "@stellar/stellar-sdk";

import { Server } from "@stellar/stellar-sdk/rpc";

async function extendContractWasmTTL(contractId, sourceKeypair) {
  const server = new Server("https://soroban-testnet.stellar.org");

  // Create a new transaction builder
  const account = await server.getAccount(sourceKeypair.publicKey());
  const fee = "200100"; // Base fee plus resource fee

  // Get the contract instance
  const contract = new StellarSdk.Contract(contractId);
  const instance = contract.getFootprint();

  // Set the Soroban data and create an operation to extend the contract's TTL
  const sorobanData = new StellarSdk.SorobanDataBuilder()
    .setResourceFee(200_000)
    .setReadOnly([instance])
    .build();
  const transaction = new StellarSdk.TransactionBuilder(account, {
    fee,
    networkPassphrase: StellarSdk.Networks.TESTNET, // Use appropriate network
  })
    .setSorobanData(sorobanData)
    .addOperation(
      StellarSdk.Operation.extendFootprintTtl({
        extendTo: 500_000,
      }),
    )
    .setTimeout(30)
    .build();

  // Sign and submit the transaction
  transaction.sign(sourceKeypair);
  const result = await server.sendTransaction(transaction);

  console.log(
    "Transaction submitted. Result:",
    JSON.stringify(result, null, 2),
  );
  return result;
}

// Usage
const contractId = "CC6MWZMG2JPQEENRL7XVICAY5RNMHJ2OORMUHXKRDID6MNGXSSOJZLLF";
const sourceKeypair = StellarSdk.Keypair.fromSecret(
  "SXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
);

extendContractWasmTTL(contractId, sourceKeypair)
  .then(console.log)
  .catch(console.error);

Breaking Down the Code

Let's walk through the key parts of this function:

1. Setting up the Soroban data: The SorobanDataBuilder() is where we prep the Soroban-specific info for our transaction.

• We set a resource fee with setResourceFee(200_000). This covers the extra costs for storage and execution.
• We use setReadOnly([instance]) to tell the network which contract stuff we need to access. We're using setReadOnly() instead of setReadWrite() because we're just extending the TTL, not changing any data.

Why setReadOnly()? A few reasons:

• It's faster and uses fewer resources
• It's safer - we can't accidentally change data we're not supposed to
• The ExtendFootprintTTLOp operation needs it

2. Adding the operation: After setting up the Soroban data, we add the extendFootprintTtl operation to our transaction. We're telling it to extend the TTL to 500,000 ledgers with extendTo: 500_000.

3. What's the point? This whole process is about keeping our contract's data alive in the ledger. It's like renewing a lease - we're telling the network "Hey, keep this stuff around longer, we're still using it!"

   This is super important for contracts that need to stick around for a while. Without extending the TTL, the contract's data could expire and disappear from the ledger.

Want to dive deeper? Check out the docs on the Extend Footprint TTL operation.