How to know if a transaction went through or not? (out of gas)

Question

Apparently when sending transactions from an Account instead of a Wallet, the gas spent is small (21K), and not enough to send ether to a Contract Wallet (out of gas, so to speak).

When this happens, the transaction shouldn't go through (or be cancelled, as it says here), however it seems to still be recorded in the blockchain, why? Example.

Doesn't etherscan.io provide any clue about if the transaction ended up being valid or not? In this case it should be marked as CANCELLED/INVALID in that URL, as far as I understand.

Answer 1

Using etherscan blockchain explorer

In etherscan, look for the TxReceipt Status which will have Fail in red, or Success in green.

Example of a failure: https://ropsten.etherscan.io/tx/0x67a5f6442f49a5da6ff8682250a8eef899d9dc0c5adf20b683709433902b5956

Using the receipt

eth.getTransactionReceipt(transactionHash) will return a status field that has a value of 0 when a transaction has failed and 1 when the transaction has succeeded.

Here's an example showing the status field:

{ blockHash: '0xb1fcff633029ee18ab6482b58ff8b6e95dd7c82a954c852157152a7a6d32785e',
  blockNumber: 4370000,
  contractAddress: null,
  cumulativeGasUsed: 21000,
  gasUsed: 21000,
  logs: [],
  logsBloom: '0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000',
  root: null,
  status: 1, // **** HERE IS THE STATUS FIELD *****
  transactionHash: '0x1421a887a02301ae127bf2cd4c006116053c9dc4a255e69ea403a2d77c346cf5',
  transactionIndex: 0 }

More details here.

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Historical

To see if a transaction ran out of gas, you can input the transaction (hash) in https://live.ether.camp and then click on "VM Trace". (For the testnet Morden, use https://morden.ether.camp)

Or plug in the transactionHash in this url:

https://live.ether.camp/transaction/<transactionHash>/vmtrace#0

For the transaction mentioned in the question, 022f440fa96eb469363804d7b6c52321d4f409fa76578cdbdc5f04ff494b1321

here is the output https://live.ether.camp/transaction/022f440fa96eb469363804d7b6c52321d4f409fa76578cdbdc5f04ff494b1321/vmtrace#0

This transaction was out of gas immediately. Some transactions may run out of gas after doing some computations, and clicking on the Operations will show each step being performed and when the out of gas happens.

Answer 2

So you transaction did went trough in the sense that it was broadcasted to the network and included in a block. However - as you have already suggested the gas you payed was not sufficient for this transaction. To prevent corrupted states in this case all the effects a transaction has will be rolled back. The only effect is that costs for the gas (in Ether) will be reduced from your account and credited to the miner who included the transaction in a block.

On https://etherscan.io/ there is no clear indication whether or not the gas was sufficient. However - the site states the "Cumulative Gas Used" and if it is equal to the "Gas" (the gas limit you set) than this is a very strong indicator that the transaction ran out of Gas. (In theory it could have indeed used that exact amount but this is very unlikely)

http://frontier.ether.camp/ is a more sophisticated block explorer and here you can see whether or not the "out of gas" exception was thrown.

Answer 3

Just to clarify to the above question, Etherscan now does show if there is an error during the contract execution. A red remark indicates an error and a green remark indicates a confirmed contract invocation.

Most of the exceptions for failed contracts are due to "out of gas". And as PaulS + mKoeppelmann has stated above, one way to determine if you have run out of gas is to match the gasSent == gasUsed. However, solely using this method would be inaccurate as there can be other exceptions that the contract first hits before it runs out of gas

Answer 4

The transaction itself is valid and so it's in the blockchain and picked up by all block explorers. But because it did not specify enough gas the wallet contract code is reverted and so no ether transfer takes place. The insufficient gas specified will still be consumed.

The https://live.ether.camp/ block explorer will indicate that the transaction was cancelled and if you examine the vmtrace view you will see that it ran out of gas.

Answer 5

If you want to determine how you've run out of gas programmatically, instead of after the fact debugging, see:

How do I know when I've run out of gas programmatically?