Gas required exceeds allowance truffle migrate

Question

Hi i am trying to work truffle migrate and firstly it start to Migration.sol and then Election.sol. When start to deploy ELection.sol it throws following error. What should i write gas:270000 instead of this value?Because i tried a lot of number like 470000 or 100000, 300000 doesnt work. Should i increase number or decrease?

truffle migrate --reset --network rinkeby

"Election" received a generic error from Geth that can be caused by hitting revert in a contract constructor or running out of gas. * Returned error: gas required exceeds allowance (2700000) or always failing transaction.

Election.sol

     pragma solidity 0.5.8;

     contract Election {
      // Model a Candidate
          struct Candidate {
          uint id;
          string name;
          uint voteCount;
     }

// Read/write Candidates
mapping(uint => Candidate) public candidates;
// Store Candidates Count
uint public candidatesCount;

 constructor() public {
    addCandidate("Candidate 1");
    addCandidate("Candidate 2");
}

function addCandidate (string  memory _name) private {
    candidatesCount ++;
    candidates[candidatesCount] = Candidate(candidatesCount, _name, 0);
}
 }

Migrations.sol

   pragma solidity >=0.4.21 <0.6.0;

   contract Migrations {
   address public owner;
   uint public last_completed_migration;

   constructor() public {
     owner = msg.sender;
   }

   modifier restricted() {
     if (msg.sender == owner) _;
   }

   function setCompleted(uint completed) public restricted {
     last_completed_migration = completed;
   }

   function upgrade(address new_address) public restricted {
     Migrations upgraded = Migrations(new_address);
     upgraded.setCompleted(last_completed_migration);
   }
  }

Genesis.file

   {
"config": {
    "chainId": 88888,
    "homesteadBlock": 0,
    "eip155Block": 0,
    "eip158Block": 0
},
"coinbase" : "0x0000000000000000000000000000000000000000",
"difficulty" : "0x1",
"extraData" : "0x00",
"gasLimit" : "0x47e7c5",
"nonce" : "0x0000000000000042",
"timestamp" : "0x00",
"alloc" :{
    "0x560ae6e63f0e79c9027a590900291399cc954f00": {"balance": "0xffffffffffffffffffffffff"}
}

}

Output:

   1_initial_migration.js
   ======================

   Replacing 'Migrations'
   .......
   then

   2_deploy_contracts.js
   =====================

   Replacing 'Election'
   Error: Error: Error:  *** Deployment Failed ***

truffle.config

   rinkeby: {
  host: "127.0.0.1",     // Localhost (default: none)
  port: 8545,            // Standard Ethereum port (default: none)
  network_id: "4",       // Any network (default: none) (Rinkeby's id 
   is given)
  from:"address",
  gas: 3000000  
 }

Answer 1

This error is not associated with the Gas value.

You need to set byzantiumBlock in the config section of your genesis.json file.

"config": {
    "chainId": 88888,
    "homesteadBlock": 0,
    "eip155Block": 0,
    "eip158Block": 0,
    "byzantiumBlock": 0
},

Since your genesis file has been updated now, you need to create new node and new address. And then try migrating your contracts with that account.

About the estimation of Gas value, what you can do is deploy the contract on Remix first. Try providing the Gas value there. If it deploys successfully, that means the Gas value is okay.

Edited Answer:

Transaction exited after consuming all gas:

This issue is related to the fact that truffle is using solidity compiler 0.5.8 which causes an issue of interaction with contracts.

I faced the same issue. Downgrading Truffle from v5.0.30 to v5.0.5 fixed the issue.

npm i -g [email protected]

And then used solidity version ^0.5.0 in both Migrations and Election contract.

Provide gas: 3000000 in your truffle-config.js file.