Function MainchainRPCCheck

src/init.cpp:1188–1238

This function checks that the RPC connection to the parent chain node * can be attained, and is returning back reasonable answers. */

 * can be attained, and is returning back reasonable answers.
 */
bool MainchainRPCCheck()
{
    // Check for working and valid rpc
    // Retry until a non-RPC_IN_WARMUP result
    while (true) {
        try {
            // The first thing we have to check is the version of the node.
            UniValue params(UniValue::VARR);
            UniValue reply = CallMainChainRPC("getnetworkinfo", params);
            UniValue error = reply["error"];
            if (!error.isNull()) {
                // On the first call, it's possible to node is still in
                // warmup; in that case, just wait and retry.
                if (error["code"].get_int() == RPC_IN_WARMUP) {
                    UninterruptibleSleep(std::chrono::milliseconds{1000});
                    continue;
                }
                else {
                    LogPrintf("ERROR: Mainchain daemon RPC check returned 'error' response.\n");
                    return false;
                }
            }
            UniValue result = reply["result"];
            if (!result.isObject() || !result.get_obj()["version"].isNum() ||
                    result.get_obj()["version"].get_int() < MIN_MAINCHAIN_NODE_VERSION) {
                LogPrintf("ERROR: Parent chain daemon too old; need Bitcoin Core version 0.16.3 or newer.\n");
                return false;
            }

            // Then check the genesis block to correspond to parent chain.
            params.push_back(UniValue(0));
            reply = CallMainChainRPC("getblockhash", params);
            error = reply["error"];
            if (!error.isNull()) {
                LogPrintf("ERROR: Mainchain daemon RPC check returned 'error' response.\n");
                return false;
            }
            result = reply["result"];
            if (!result.isStr() || result.get_str() != Params().ParentGenesisBlockHash().GetHex()) {
                LogPrintf("ERROR: Invalid parent genesis block hash response via RPC. Contacting wrong parent daemon?\n");
                return false;
            }
        } catch (const std::runtime_error& re) {
            LogPrintf("ERROR: Failure connecting to mainchain daemon RPC: %s\n", std::string(re.what()));
            return false;
        }

        // Success
        return true;
    }
}

bool AppInitInterfaces(NodeContext& node)
{