Blockchain Platforms Resources

A common error message that Kaleido users have encountered when trying to execute smart contract transactions is “out-of-gas.” This document describes some of the known causes and potential fixes. Here are some definitions of terms related to gas. The referenced eth APIs are part of the Web3.js library. gas: unit of measurement for the computational work of running transactions or smart contracts in the Ethereum network gasLimit: maximum amount of gas that can be spent on all transactions within a single block. This is not configurable by Kaleido users. Listed as gasLimit in output of eth.getBlock("") The miner of a new block can set the gas limit within +/- 0.1 % of the parent block’s gas limit gas provided: maximum amount of gas you’re willing to spend on a particular transaction Listed as gas in output of eth.getTransaction("") gasPrice: the amount of Ether you’re willing to pay for every unit of gas, measured in Gwei (1 ETH = 1M Gwei) Listed as gasPrice in output of eth.getTransaction("") Common Symptoms, Causes and Solutions “Gas provided” for transaction is not high enough to cover the gas needed to execute the transaction. Likely error message: intrinsic gas too low. Fix: Supply a higher gas amount, or use a client like the Kaleido REST API Gateway that automatically estimates gas for your transactions (importantly also adding a 20% contingency on top before submission) The from account does not have enough Ether to execute transaction. Likely error message: insufficient funds for gas * price + value Note: This will only occur if the gasPrice for the transaction is set to some value other than the default 0. Fix: Use a debugger like Remix to debug your infinite loop Infinite loop or other unbounded processing error in smart contract code Likely error message TX ran out of gas before completion Fix: Use a debugger like Remix to debug your infinite loop Contract is not compiled for the correct EVM version Likely error message gas required exceeds allowance or always failing transaction Fix: Compile with --evm-version byzantium Note: If you need more recent opcodes, please contact us to confirm the hard fork that is supported in Kaleido and meets your needs. Contract has reverted Likely error message gas required exceeds allowance or always failing transaction Fix: Run eth_call with exactly the same parameters, then process the output per the Solidity control structures doc to get the error message of the revert Note: Some web3 interfaces, including Truffle, and the Kaleido REST API Gateway, perform an eth_call automatically for you when this occurs during gas estimation and return the error string, rather than the generic message

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One tricky aspect to timestamps using the now variable in Ethereum is the use of different units, depending on environment type. Unlike vanilla Ethereum implementations, timestamps in an environment with a Quorum client and Raft consensus (Quorum-Raft) are represented in nanoseconds because the Raft consensus can produce more than one block per second. Contrastingly, Quorum-IBFTand Geth-PoA (Proof-of-Authority) environments use timestamps whose units are denoted in seconds. In all three environment types, the now keyword provides the timestamp of the most recent block in UNIX Epoch time format (time since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970). NOTE: The difference in timestamp units can be the root-cause of out-of-gas errors if you transport the same timestamp-dependent require statements from smart contract code in one environment type to another.

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You do not need to purchase any Ether, token or cryptocurrency to run environments and execute transactions. Kaleido provides private blockchain implementations. Transactions must specify a value to the gas parameter in order to be a properly formed object, however, unlike typical Mainnet transactions, the gasPrice parameter can be set to 0. In scenarios where transaction fees are desired, members can take advantage of the Kaleido Ether Pool; an environment-specific pool of 1 Billion ether, that is automatically generated in the genesis block of the chain. Any member of the consortium can access this pool through the UI or via the /fundaccount API. The pool can be utilized in one of two ways. Users can access the ether on a need-by-need basis, or the pool can be immediately drained by the environment creator and then disseminated in accordance with some agreed upon policies.

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