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Lightecho Oracle - Oracle smart contract for Soroban

Lightecho is a Stellar Oracle for emerging markets data and XLM volatility feeds. Oracles are bridge technologies that connect blockchain systems with the outside world, enabling smart contracts to securely access external data. In the realm of Stellar, a platform designed for the fast and cost-efficient transfer of value across the globe, Lightecho Oracle emerges as a critical tool, especially for Soroban — Stellar's smart contracts platform.

Lightecho is dedicated to delivering real-time, reliable market data and XLM volatility feeds, addressing a significant gap in emerging markets. These markets often face challenges such as limited access to traditional banking services and financial volatility.

PRODUCTION Official Contracts:

TESTNET Official Contracts:

Roadmap

  • Complete JS examples ( playcode / fiddle updates)
  • Improve documentation
  • Deploy market data feeds for XLM/EUR, XLM/USD, XLM/ARS, XLM/BRL, XLM/NGN, XLM/NGN_2 and a test of XLM Vol and many more
  • Confirm prices resolution
  • Improved documentation
  • Bounty for usage
  • Soroban go live (pilot mode)
  • list of initially supported assets
  • updates as to data sources
  • architecture and failover (currently a 2 + 1 model)
  • licensing

This repository contains:

In this README

FAQ

  • What is this repository? This repository is a monorepo that contains multiple software related to the Lightecho Oracle, including the Oracle source code itself.
  • What is the Lightecho Oracle? It's BP Venture's implementation of a blockchain oracle for the Stellar blockchain. It's built to run in the Soroban network, a smart contracts layer built on the Stellar blockchain. See here for more details about our motivation.
  • What is the target audience for this repository? Smart contract developers who are looking for Oracle contracts that they can integrate into and consume prices from.
  • How do I run this software? Since this repository contains multiple software components, you can run each component separately. For example, if you just wanna see the last price in the Oracle, check out the Web app. If you want a terminal-based CLI for interacting with the Oracle, check out the Python CLI. If you're developing a smart contract and you need to fetch an exchange rate, check out our (outdated) example on how to consume the Oracle from other contracts. If you want to run the Oracle contract, you can run build it and run it locally or deploy to Stellar testnet for example. Stellar has many guides that cover a wide range of use cases.

Infrastructure

flowchart TD
    deploy[Deploy Oracle to blockchain]-->initialize[Initialize Oracle with admin, base, decimals, etc]
    initialize-->blockchain_contract
    price_aggregator["Price aggregator (not open-source)"]-->post_prices["POST /db/add-prices"]
    subgraph database [Price Database]
        db[SQLite database file]
    end
    subgraph oracle_api ["Oracle API (see oracle-onchain/api)"]
      post_prices-->save_to_db[Save prices to database]
      save_to_db-->db
    end
    subgraph oracle_background_scripts ["Oracle background scripts (see oracle-onchain/sep40/cli/scripts)"]
      db-->read_prices_from_db[Read prices from API database]
      read_prices_from_db-->check_timestamps[Check price timestamps]
      check_timestamps-->add_prices["Add prices to blockchain Contract via add_prices()"]
    end
    subgraph soroban_blockchain [Soroban Blockchain]
      add_prices-->blockchain_contract[Contract inside blockchain]
    end
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Price Sources

Each source is represented by an integer in the blockchain contract. To fetch the last price of USD from Coinbase for example, you can use the CLI:

./cli oracle lastprice_by_source 1 other USD

TESTNET Official Sources for prices:

0 - BPV aggregator
1 - Coinbase

A brief timeline of the Lightecho Oracle

  • April 2023: Beginning of development of the Lightecho Oracle.
  • June 2023: Beginning of development of the Oracle SDKs for Python and JavaScript.
  • July 2023: First official launch of the Oracle MVP. Internally storing all prices in a single ledger entry of type Map.
  • July 2023: BPV wins Stellar Community Award for Soroban development.
  • November 2023: We began noticing issues related to using Map to store the prices in the blockchain. The main issue being the size limit for a single ledger entry, and the expensive fees consumed to add and retrieve prices from the contract.
  • December 2023: Started discussion in Discord regarding fees and the use of Map.
  • January 2024: After much discussion, testing, and planning, we decided to rewrite the contract using a more lightweight approach: store each price in its own dedicated ledger key in temporary storage. Each price ledger key is an integer of type u128 with this structure: [first 32 bits - source][next 32 bits - asset identifier][next 64 bits - timestamp]. Using this new lightweight approach allowed us to reduce fee costs in 95% compared to the previous implementation using Map, and removed all the scalability issues we had when using Map. More curious about the code structure? See here how we generate the ledger key for a given price.
  • January 2024: Second official launch of the Oracle, now using the new lightweight structure to store the prices. March 5 2024: Lauched the smart contract in Production Pilot [See here] (https://stellar.expert/explorer/public/tx/c74242b939e6d7b492d1297d239807b2cf766d7c1bfaa0286e9ffef63bfb3b9e)

(For BPV developer) Install the price feed script

The price feed is a script that puts the prices into the blockchain contract.

Important

CLI must be already setup and configured via local_settings.py. See instructions.

Start by installing the systemd container:

sudo apt install systemd-container

Now, login into the systemd container and copy the systemd service unit files:

sudo machinectl shell myusername@  # replace myusername with your Linux username
mkdir -p ~/.config/systemd/user/
cp -v init/systemd/* ~/.config/systemd/user/

Go to ~/.config/systemd/user/ and update the .service files (that you copied) with the correct paths:

...

[Service]
# replace /path/to/ with the correct path
ExecStart=/path/to/lightecho-stellar-oracle/oracle-onchain/sep40/cli/scripts/bump_instance.sh

...

Enable and start the services:

./run deploy

Additional commands:

./run status  # check status of API and Feed
./run restart  # restart API and Feed

# systemd helper
./systemd-status.sh

# to see logs
journalctl --user -u feed_bulk_from_db
journalctl --user -u bump_instance

Featured projects

Have a project that uses our Oracle? Feel free to share with us and we'll be happy to list it here!

https://lightecho.io

Made by BP Ventures

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A Stellar Soroban Oracle contract implemented by BP Ventures

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