pyth-aptos-js

Pyth Aptos JS

Pyth provides real-time pricing data in a variety of asset classes, including cryptocurrency, equities, FX and commodities. This library allows you to use these real-time prices on Aptos networks.

Installation

npm

$ npm install --save @pythnetwork/pyth-aptos-js

Yarn

$ yarn add @pythnetwork/pyth-aptos-js

Quickstart

Pyth stores prices off-chain to minimize gas fees, which allows us to offer a wider selection of products and faster update times. See On-Demand Updates for more information about this approach. To use Pyth prices on chain, they must be fetched from an off-chain price service. The AptosPriceServiceConnection class can be used to interact with these services, providing a way to fetch these prices directly in your code. The following example wraps an existing RPC provider and shows how to obtain Pyth prices and submit them to the network:

const connection = new AptosPriceServiceConnection(
  "https://xc-testnet.pyth.network"
); // See Price Service endpoints section below for other endpoints

const priceIds = [
  // You can find the ids of prices at https://pyth.network/developers/price-feed-ids#aptos-testnet
  "0xf9c0172ba10dfa4d19088d94f5bf61d3b54d5bd7483a322a982e1373ee8ea31b", // BTC/USD price id in testnet
  "0xca80ba6dc32e08d06f1aa886011eed1d77c77be9eb761cc10d72b7d0a2fd57a6", // ETH/USD price id in testnet
];

// In order to use Pyth prices in your protocol you need to submit the price update data to Pyth contract in your target
// chain. `getPriceUpdateData` creates the update data which can be submitted to your contract. Then your contract should
// call the Pyth Contract with this data.
const priceUpdateData = await connection.getPriceFeedsUpdateData(priceIds);

// Create a transaction and submit to your contract using the price update data
const client = new AptosClient(endpoint);
let result = await client.generateSignSubmitWaitForTransaction(
  sender,
  new TxnBuilderTypes.TransactionPayloadEntryFunction(
    TxnBuilderTypes.EntryFunction.natural(
      "0x..::your_module",
      "do_something",
      [],
      [priceUpdateData]
    )
  )
);

your_module::do_something should then call pyth::update_price_feeds before querying the data using pyth::get_price:

module example::your_module {
    use pyth::pyth;
    use pyth::price_identifier;
    use aptos_framework::coin;

    public fun do_something(user: &signer, pyth_update_data: vector<vector<u8>>) {
        // First update the Pyth price feeds. The user pays the fee for the update.
        let coins = coin::withdraw(user, pyth::get_update_fee(pyth_update_data));

        pyth::update_price_feeds(pyth_update_data, coins);

        // Now we can use the prices which we have just updated
        let btc_usd_price_id = price_identifier::from_byte_vec(
            x"e62df6c8b4a85fe1a67db44dc12de5db330f7ac66b72dc658afedf0f4a415b43");
        let price = pyth::get_price(btc_usd_price_id);

    }
}

We strongly recommend reading our guide which explains how to work with Pyth price feeds.

Off-chain prices

Many applications additionally need to display Pyth prices off-chain, for example, in their frontend application. The AptosPriceServiceConnection provides two different ways to fetch the current Pyth price. The code blocks below assume that the connection and priceIds objects have been initialized as shown above. The first method is a single-shot query:

// `getLatestPriceFeeds` returns a `PriceFeed` for each price id. It contains all information about a price and has
// utility functions to get the current and exponentially-weighted moving average price, and other functionality.
const priceFeeds = await connection.getLatestPriceFeeds(priceIds);
// Get the price if it is not older than 60 seconds from the current time.
console.log(priceFeeds[0].getPriceNoOlderThan(60)); // Price { conf: '1234', expo: -8, price: '12345678' }
// Get the exponentially-weighted moving average price if it is not older than 60 seconds from the current time.
console.log(priceFeeds[1].getEmaPriceNoOlderThan(60));

The object also supports a streaming websocket connection that allows you to subscribe to every new price update for a given feed. This method is useful if you want to show continuously updating real-time prices in your frontend:

// Subscribe to the price feeds given by `priceId`. The callback will be invoked every time the requested feed
// gets a price update.
connection.subscribePriceFeedUpdates(priceIds, (priceFeed) => {
  console.log(
    `Received update for ${priceFeed.id}: ${priceFeed.getPriceNoOlderThan(60)}`
  );
});

// When using the subscription, make sure to close the websocket upon termination to finish the process gracefully.
setTimeout(() => {
  connection.closeWebSocket();
}, 60000);

Example

This example shows how to update prices on an Aptos network. It does the following:

1. Fetches update data from the Price Service for the given price feeds.
2. Calls the Pyth Aptos contract with the update data.

You can run this example with npm run example-relay. A full command that updates BTC and ETH prices on the BNB Chain testnet network looks like this:

export APTOS_KEY = "0x...";
npm run example-relay -- --endpoint https://xc-testnet.pyth.network --price-ids 0xf9c0172ba10dfa4d19088d94f5bf61d3b54d5bd7483a322a982e1373ee8ea31b 0xca80ba6dc32e08d06f1aa886011eed1d77c77be9eb761cc10d72b7d0a2fd57a6 --full-node https://fullnode.testnet.aptoslabs.com/v1 --pyth-contract 0xaa706d631cde8c634fe1876b0c93e4dec69d0c6ccac30a734e9e257042e81541

Price Service endpoints

We provide public endpoints for the price service, although it is strongly recommended to host your own instance.

Aptos Network	Price Service URL
Testnet	https://xc-testnet.pyth.network
Mainnet	https://xc-mainnet.pyth.network