Provable API for calling ETH-USD price in a contract

Question

This contract is hosted at https://github.com/provable-things/ethereum-examples/blob/master/solidity/truffle-examples/kraken-price-ticker/contracts/KrakenPriceTicker.sol

I have made the constructor payable and transferring ether while deploying, The original contract was calling update method recursively from __callback but I have removed it.

pragma solidity >= 0.5.0 < 0.6.0;

//import "github.com/provable-things/ethereum-api/provableAPI.sol";
import "https://github.com/provable-things/ethereum-api/provableAPI_0.5.sol";

contract KrakenPriceTicker is usingProvable {

    string public priceETHXBT;

    event LogNewProvableQuery(string description);
    event LogNewKrakenPriceTicker(string price);

    constructor()
        public
        payable
    {
        provable_setProof(proofType_Android | proofStorage_IPFS);
        update(); // Update price on contract creation...
    }

    function __callback(
        bytes32 _myid,
        string memory _result,
        bytes memory _proof
    )
        public
    {
        require(msg.sender == provable_cbAddress());
        // update(); // Recursively update the price stored in the contract...
        priceETHXBT = _result;
        emit LogNewKrakenPriceTicker(priceETHXBT);
    }

    function update()
        public
        payable
    {
        if (provable_getPrice("URL") > address(this).balance) {
            emit LogNewProvableQuery("Provable query was NOT sent, please add some ETH to cover for the query fee!");
        } else {
            emit LogNewProvableQuery("Provable query was sent, standing by for the answer...");
            provable_query(60, "URL", "json(https://api.kraken.com/0/public/Ticker?pair=ETHXBT).result.XETHXXBT.c.0");
        }
    }
}

I cant even deploy this contract, Error I am getting is

VM error: revert.
revert  The transaction has been reverted to the initial state.
Note: The called function should be payable if you send value and the value you send should be less than your current balance.  Debug the transaction to get more information

Answer 1

I was able to deploy that contract. You cannot deploy it on a private/local chain, since the Provable service must be available in the chain. Fortunately the Provable service is available on all testnets. Further, you could implement a bridge to run it on a local chain, see https://docs.provable.xyz/#integrations-alternative-public-chains.