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I am using Truffle Contract to call a Smart Contract method that writes to the ethereum blockchain. My web3 client is connected to my own Open Ethereum node. Below is the code (nodejs) that I am using to send the transaction to blockchain. I would expect, since this is an asynchronous call that the response would be immediately and the transaction hash value would be returned. However, this is NOT happening. The only time I get a response is after the transaction is mined. I can't rely on this because my front-end client will time out (30 secs for AWS API Gateway). What am I doing wrong? I can see all the eth_getTransactionReceipt json calls in my OE log, being called back to back until the transaction is mined.

async function sendTransClaimProperty(_instance) {

    var result;
    
    try {
      
      result = await web3.eth.personal.unlockAccount(web3.eth.defaultAccount, process.env.oranges, null);
      console.log(web3.eth.defaultAccount + " Account UnLocked", result);
      
      if (result) {
            var claimState = "Property Claimed on " + new Date();
            console.log("Calling Ethereum Node at " + new Date());
            
            result = await _instance.claimProperty.sendTransaction(claimTitle,claimHash,claimTime,claimCreditCardTx,claimClientIP,claimState);
                
            console.log("Return from Ethereum Node result", result);
            console.log("Return from Ethereum Node. TX", result.tx);
            return { response: "OK", transHash: result.tx };
            
      } 
    }
    catch (error) {
      
      console.log("Error Sending Transaction");
      console.log(error.message);
      return { response: "FAIL", message: "Error claiming property " + error.message };
      
    }
    
  }
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1 Answer 1

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To obtain the transaction hash without waiting you have to use the events system

const res = _instance.claimProperty(claimTitle,...);
res.on('transactionHash', (hash) => {
  console.log('TxHash', hash);
});

You will find some other details at Truffle reference.

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  • Ismael, Thanks for the advice. It did not work. The response from the async call returned this INFO Response is Promise { <pending>, _events: Events <[Object: null prototype] {}> {}, emit: [Function: emit], on: [Function: on], once: [Function: once], off: [Function: removeListener], listeners: [Function: listeners], addListener: [Function: on], removeListener: [Function: removeListener], removeAllListeners: [Function: removeAllListeners] This async call however, is part of a synchronous function call. Maybe that's the problem. I will continue to try
    – Kevin Melberger
    Jun 21, 2020 at 13:02
  • @KevinMelberger What did you try? and why do you say it doesn't work?
    – Ismael ♦
    Jun 21, 2020 at 15:48
  • I added the event emitter code, but it does not work. Everything I tried will not get me back the transaction hash BEFORE the transaction is mined. Code example below: _instance.claimProperty.sendTransaction(claimTitle,claimHash,claimTime,claimCreditCardTx,claimClientIP,claimState) .on('transactionHash', function(hash){ txHash = hash; console.log("Return from Ethereum Node. TX ", hash); }) .on('error',console.error);
    – Kevin Melberger
    Jun 22, 2020 at 2:32

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