Analyzing pending transactions in Ethereum
Orphaned transactions are a common problem in Ethereum. It is when a transaction is sent but never added to the blockchain for various reasons, such as invalid or incomplete input data. In this article, we will explain how to analyze an orphaned operation using debug.log.
What does debug.log output?
When your computer syncs with the Ethereum network, it performs a series of operations to check the validity of each block and ensure that all transactions are included in the blockchain. If the transaction is sent but not included in the blockchain, you will see errors such as “ERROR: FetchInputs(): 5b5e32cc97 previous mempool tx not found” or “ERROR: FetchInputs(): 5b5e32cc97 stored orphan tx”.
Understanding debug.log output
The output of the debug log provides valuable information about the operation being analyzed. Here is the meaning of each line:
- ERROR: FetchInputs(): 5b5e32cc97 Mempool Tx prev not found e99babf87a:
- FetchInputs() is a function that fetches the inputs for a given operation.
- “e99babf87a” is the mempool hash of the previous transaction (mempool is a queue of pending transactions).
- “Protected by orphan TX 5b5e32cc97 (mapsz 414)”:
- This line indicates that the analyzed transaction (“5b5e32cc97”) was previously sent but not included in the blockchain.
- The “(mapsz 414)” part is the map size that helps narrow down possible locations for the orphan operation.
Analyzing a failed transaction
To analyze an orphaned operation using debug.log, follow these steps:
- Print debug.log output: Use a tool like geth-cli or mainnet-ethers.js to print debug.log output. This will give you error messages and other important information.
- Find orphaned operations: Look for lines that indicate an orphaned operation, such as “ERROR: FetchInputs() : 5b5e32cc97 mempool Tx prev not found”.
- Determine map size: Check the map size to determine which part of the mempool the operation was sent to but not included.
- Check previous operations: Look for other error messages that indicate a previous operation in memory, such as “ERROR: FetchInputs() : e99babf87a”.
- Use tools like ethers.js or solidity-coverage to analyze the transaction: These tools can help you understand the contract logic and identify potential problems with the transaction.
Example use case
Let’s say you have a contract that commits a new transaction but never puts orphaned inputs into the blockchain. You can use debug.log to analyze the operation and determine where the error occurred:
const debug = require('debug')('ethers:analyze-orphaned-transaction');
// Print Debug.log output
Console.log(debug.log());
// Find orphaned transactions
for (let i = 0; i < 10000; i++) {
const txId = ethers.utils.generateTransaction().hex();
debug.log(TxId: ${txId} orphaned operation found);
}
// Set map size and previous operations
const orphans = [];
for (let i = 0; i < 100000; i++) {
const txId = ethers.utils.generateTransaction().hex();
if (!debug.log.includes(ERROR: FetchInputs() : ${txId} previous mempool Tx not found)) {
orphans.push(txId);
}
}
console.log(orphans);
// Use tools to analyze the transaction
const contract = Ether.contract.fromBytes(buffer);
const tx = contract.methods.myFunction().send();
By analyzing the debug log, you can identify potential problems with orphaned transactions and take steps to resolve them. Remember to always be cautious when working with Ethereum and consider using tools like solidity-coverage or Ethers.js to understand the contract logic.