Inconsistent Result for Web3 Constant Method Call

Question

Deployed a local private Ethereum environment. While trying to invoke a constant method of a solidity contract getting inconsistent results.

Sometimes the result is returned and mostly not.

When I tried to fetch the data from geth command line was able to successfully list down the results every time.

In the Nodejs code below created a loop of 20 iterations to fetch the asset price. Sometimes 10-15 times the result is returned correctly and many a times in none of the iterations result is found rather it says 0.

Contract

pragma solidity ^0.4.9;

contract Asset {

    address public owner;
    struct Asset {
        string title;
        string description;
        uint  assetTime;
        uint price;
    }

    Asset[] public  assets;

    event LogAssetAdded(address indexed fromAddress, string description);

    // add asset
    function addAsset(string  description1, string title1, uint price1,uint assetTime1) 
      returns (uint, string, string, uint, uint) {
        uint assetID = assets.length++;
        Asset o = assets[assetID];

        o.description = description1;
        o.assetTime=assetTime1;
        o.title = title1;
        o.price = price1;

        LogAssetAdded(msg.sender, description1);

        return (assetID, assets[assetID].description, assets[assetID].title, assets[assetID].price, 
          assets[assetID].assetTime);
    }

    //return the  number of assets 
    function assetCount() public constant returns(uint) {
        uint assetCount =assets.length;
        return(assetCount);
    }

    function getAssetPrice(uint assetID) public constant returns(uint) {
        return assets[assetID].price;
    }

    function getDefAssetPrice() public constant returns(uint) {
        return assets[assets.length-1].price;
    }

    function getDefAssetTitle() public constant returns(string) {
        return assets[assets.length-1].title;
    }

    function getDefAssetTime() public constant returns(uint) {
        return assets[assets.length-1].assetTime;
    }
}

NodeJs Client Code

const rpcURL = 'http://localhost:9081'
var Web3 = require('web3');
var web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:9081"));

const fs = require("fs");

let abi ='<<Apply ABI>>';

let bytecode = '<<Apply Bytecode >>'
let gasEstimate = web3.eth.estimateGas({data: bytecode});

let assetContract = web3.eth.contract(JSON.parse(abi));
const account = '<<Provide from account>>';

var contractAddress = '<<Provide Contract Address>>';

var ctr1 = 0;
var contract = assetContract.at(contractAddress);

// Method to create asset
function addAsset(){
    contract.addAsset.sendTransaction("Asset Description", " Asset Title", 41202, 41203, {from: account, gas: 400000} 
    , function(err, result){
        if(err){
            console.log('Error '+ err);    
        }
        else{
            console.log('Transaction Hash: '+ result);
            getAssetPrice();
        }
    });
}

// Method to fetch asset price
function getAssetPrice(){  
    for(var i=0;i<20;i++){
      contract.getAssetPrice(0, (error, result) => {
        if (!error && result>0) {
            ctr1++;
            console.log(ctr1 +": getAssetPrice: "+ result);
        }
        if (!error){
             console.log("Error occurred: "+ error);
        }
    });
}

addAsset();
//getAssetPrice()

Dependencies

"web3": "^0.19",
"solc": "^0.4.9"

Geth Version

 v1.9.0 windows-amd64, go1.10.3

Geth Instance Command

geth --mine --minerthreads=1 --datadir D:/Ethereum/env-II/data/node1 --networkid 4224 --nodiscover --rpc --rpcport "9081" --port "30301" --rpccorsdomain "*" --nat "any" --rpcapi eth,web3,personal,net,miner --unlock 0 --password "D:/Ethereum/env-II/pwd.txt"  --rpcaddr 0.0.0.0 --verbosity 2 console

Geth command line result

> var assetContractRef = eth.contract('<<Contract abi>>');
> var assetContract = assetContractRef.at('<<Contract address>>')
> assetContract.getAssetPrice(1);
> 41202

Result on invoking with Call

Option 1: contract.getAssetPrice(0).call((error, result) => {                            

TypeError: contract.getCallPrice(...).call is not a function

Option 2: contract.getAssetPrice.call(0, (error, result) => {

Faced same result i.e. inconsistent output.

Note

I have tried this implementation, with Web3 1.0.0-beta.52 as well with a bit modified nodejs code i.e. specific to the web3 1.0.0 signatures, but have faced the same inconsistent results. If required could share that version of Nodejs code as well.

Answer 1

You might want to use .call() when invoking constant (view) methods. Check out this page of the Web3js docs to get familiar: https://web3js.readthedocs.io/en/1.0/web3-eth-contract.html#methods-mymethod-call

At a glance, I think all you would have to change is this line:

contract.getAssetPrice(0, (error, result) => {

To this:

contract.getAssetPrice(0).call((error, result) => {

Answer 2

You are sending a request many times within a certain period of time. Your result might be due to the TCP connection. You are using http , try using websocket as a provider.

var web3 = new Web3(new Web3.providers.WebsocketProvider("http://localhost:9081"));