Oracles - Smart Contract Data Provider

Overview

Oracles are smart contracts which have a connection to the outside world. Other contracts can request outside data from them. For example making HTTP GET/POST transactions to retrieve a status on a package delivery.

Acknowledgements

Based of Alex Bergszaszi's original TinyOracle Smart Contract. With Improvements from Oleg Abrosimov and Sam Bacha (Block Array Corporation)

License

Copyright (C) Block Array Corporation

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

 www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Deploy

npm install

Run

export ORACLE_SENDER_PRIVATE_KEY=1ce642301e680f60227b9d8ffecad474f15155b6d8f8a2cb6bde8e85c8a4809a
node main.js -u 'UPS-ACCOUNT' -p 'UPS-PASSWORD' -l 'UPS-LICENSE' --dispatch 0x89960f0D99a6d092633329EdD24E7680836C8547 --sender 0x8D68583e625CAaE969fA9249502E105a21435EbF

The dispatch address is an address of the TinyOracle contract deployed. In the example the 0x89960f0D99a6d092633329EdD24E7680836C8547 address is a contract deployed in the Ropsten network.

The sender address is an address from which callback function would be called. In this example the publicly known address 0x8D68583e625CAaE969fA9249502E105a21435EbF is used. It has some Ropsten Ether on a balance for tests.

Test

1. Choose ropsten network in your MetaMask wallet.
2. Copy the code below to the https://remix.ethereum.org editor and compile:

pragma solidity ^0.4.18;

//
// This is the API file to be included by a user of this oracle
//

// This must match the signature in dispatch.sol
contract TinyOracle {
  function query(bytes _query) external returns (uint256 id);
  function getResponseAddress() public constant returns (address);
}

// The actual part to be included in a client contract
contract usingTinyOracle {
  address constant tinyOracle = 0x89960f0D99a6d092633329EdD24E7680836C8547;

  modifier onlyFromTinyOracle {
    TinyOracle tiny = TinyOracle(tinyOracle);
    require (msg.sender == tiny.getResponseAddress());
    _;
  }

  function queryTinyOracle(bytes _query) internal returns (uint256 id) {
    TinyOracle tiny = TinyOracle(tinyOracle);
    id = tiny.query(_query);
  }
}

contract SampleClient is usingTinyOracle {
  bytes public response;
  uint256 theid;

  function __tinyOracleCallback(uint256 _id, bytes _response) onlyFromTinyOracle external {
    response = _response;
    theid = _id;
  }

  function query() public {
    string memory tmp = "hello world";
    query(bytes(tmp));
  }

  function query(bytes _query) public {
    queryTinyOracle(_query);
  }
}

Go to the Run tab, choose SampleClient in a dropdown list, Enter the 0x42fb9ee41AE8c6Bd33Ac3C1B3058D0Eb2980f183 address into the At Address field and press the At Address button

Call the query method without parameters to test tracking not found behavior.

Call the query method with parameter 0x315a31323334354530323035323731363838 to test tracking found behavior.

Future Improvements

Organize File Structure Add additional methods for querying Create AWS/Azure templates for 1-click launch Create notary digest of fetched data