Advanced Simulation API Usage
Learn how to use Simulation API to extract transaction information.
In this code sample, we use Simulation API to:
- Simulate a transaction in a past block, at a particular block index.
- Extract and show balance changes.
- Output values of the called smart contract function.
- Show events emitted during the simulated transaction execution.
- Display state changes.
The example simulates the execution of an existing successful transaction sent to UniswapV2Router02 on the Ethereum Mainnet to retrieve additional information. Here's the transaction calling
swapExactTokensForTokens() and exchanging 3,118.71 XCAD to USDT.{
"from": "0x1cf5cd427d0a968379bd6b5befce28d8e157ae38",
"input": "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",
"to": "0x7a250d5630b4cf539739df2c5dacb4c659f2488d",
"gas": 138864,
"gas_price": "32909736476",
"value": "0",
"access_list": []
}
The following code customizes the simulation context by:
- Simulating the transaction on the block 16533181.
- Simulating this transaction at a particular index within that block (in this case 1).
Request
Result
import axios from 'axios';
import * as dotenv from 'dotenv';
dotenv.config();
// TX in question: https://dashboard.tenderly.co/nenad/observer/tx/mainnet/0xe165a7a77aa8973ff167f70b3ecb95cce6a6c5b1350e22176ed5c0784091daa4
const simulateUniswap = async () => {
// assuming environment variables TENDERLY_USER, TENDERLY_PROJECT and TENDERLY_ACCESS_KEY are set
// https://docs.tenderly.co/other/platform-access/how-to-find-the-project-slug-username-and-organization-name
// https://docs.tenderly.co/other/platform-access/how-to-generate-api-access-tokens
const { TENDERLY_USER, TENDERLY_PROJECT, TENDERLY_ACCESS_KEY } = process.env;
const resp = await axios.post(
`https://api.tenderly.co/api/v1/account/${TENDERLY_USER}/project/${TENDERLY_PROJECT}/simulate`,
// the transaction
{
// Simulation configuration
save: false, // if true simulation is saved and shows up in the dashboard
save_if_fails: true, // if true, reverting simulations show up in the dashboard
simulation_type: 'full', // full or quick (full is default)
// network to simulate on
network_id: '1',
// simulate transaction at this (historical) block number
block_number: 16527769,
// simulate transaction at this index within the (historical) block
transaction_index: 42,
/* Standard EVM Transaction object */
from: '0x1cf5cd427d0a968379bd6b5befce28d8e157ae38',
input:
'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',
to: '0x7a250d5630b4cf539739df2c5dacb4c659f2488d',
gas: 138864,
gas_price: '32909736476',
value: '0',
access_list: [],
generate_access_list: true,
},
{
headers: {
'X-Access-Key': TENDERLY_ACCESS_KEY as string,
},
}
);
// access the transaction object
const transcation = resp.data.transaction;
// access the transaction call trace
const callTrace = transcation.transaction_info.call_trace;
// access transaction's logs
const logs = resp.data.transaction.transaction_info.logs;
console.log(
`Simulated transaction info: hash: ${transcation.hash} block number: ${transcation.block_number}`
);
// display balance changes
console.log(
'Balance changes',
'\n ' +
callTrace.balance_diff
.map(
(balance: any) =>
`${balance.address}: ${balance.original} -> ${balance.dirty} ${
balance.is_miner ? '(Miner)' : ''
}`
)
.join('\n ')
);
// display output values
console.log(
'Output values' +
'\n ' +
callTrace.decoded_output
.map(
(output: any) =>
`${output.soltype.name} ${output.soltype.type} = ${JSON.stringify(
output.value
)}`
)
.join('\n ')
);
// display events
console.log(
'Events' +
'\n ' +
logs
.map(
(log: any) =>
`${log.name} (${log.inputs
.map(
(input: any) =>
`${input.soltype.name} ${input.soltype.type} = ${input.value}`
)
.join(', ')})`
)
.join('\n ')
);
const stateDiff = resp.data.transaction.transaction_info.state_diff;
// display state changes for all affected contracts
console.log(
'State changes' +
'\n ' +
stateDiff
.map(
(diff: any) =>
`${diff.address}
${diff.soltype.name}: ${diff.soltype.type}
${JSON.stringify(diff.original)} -> ${JSON.stringify(diff.dirty)}
`
)
.join('\n ')
);
};
simulateUniswap();
Simulated transaction info: hash: 0x57be7b9d6118a0fa3fc11fa9460d93cbec8e45a7ad1d6af501a6e0f02d1bf601 block number: 16527769
Balance changes
0x1cf5cd427d0a968379BD6b5BefcE28d8e157AE38: 178649986537506409 -> 175016718720819533
0xC0E1b256DE232262134c22f73b21F756072Bfb73: 4913764247259774380 -> 4913874657421732568 (Miner)
Output values
amounts uint256[] = ["3282651314","2914031999999999475712"]
Events
Transfer (from address = 0x1cf5cd427d0a968379bd6b5befce28d8e157ae38, to address = 0x6f118ecebc31a5ffe49b87c47ea80f93a2af0a8a, value uint256 = 3282651314)
Transfer (from address = 0x6f118ecebc31a5ffe49b87c47ea80f93a2af0a8a, to address = 0x1cf5cd427d0a968379bd6b5befce28d8e157ae38, value uint256 = 2914031999999999475712)
Sync (reserve0 uint112 = 254368076784473724455687, reserve1 uint112 = 288968153842)
Swap (sender address = 0x7a250d5630b4cf539739df2c5dacb4c659f2488d, amount0In uint256 = 0, amount1In uint256 = 3282651314, amount0Out uint256 = 2914031999999999475712, amount1Out uint256 = 0, to address = 0x1cf5cd427d0a968379bd6b5befce28d8e157ae38)
State changes
0x6f118ecebc31a5ffe49b87c47ea80f93a2af0a8a
reserve0: uint112
"257282108784473723931399" -> "254368076784473724455687"
0x6f118ecebc31a5ffe49b87c47ea80f93a2af0a8a
reserve1: uint112
"285685502528" -> "288968153842"
0x6f118ecebc31a5ffe49b87c47ea80f93a2af0a8a
blockTimestampLast: uint32
1675166819 -> 1675179707
0x6f118ecebc31a5ffe49b87c47ea80f93a2af0a8a
price0CumulativeLast: uint256
"756643269219333625014234830491" -> "756717575180654871536825733691"
0x6f118ecebc31a5ffe49b87c47ea80f93a2af0a8a
price1CumulativeLast: uint256
"115330660026005862214326453602290190379962570339216427" -> "115390925201612227497765383158300036629651585476758491"
0x7659ce147d0e714454073a5dd7003544234b6aa0
_balances: mapping (address => uint256)
{"0x1cf5cd427d0a968379bd6b5befce28d8e157ae38":"13735118200000000589824","0x6f118ecebc31a5ffe49b87c47ea80f93a2af0a8a":"257282108784473723931399"} -> {"0x1cf5cd427d0a968379bd6b5befce28d8e157ae38":"16649150200000000065536","0x6f118ecebc31a5ffe49b87c47ea80f93a2af0a8a":"254368076784473724455687"}
0xdac17f958d2ee523a2206206994597c13d831ec7
balances: mapping (address => uint256)
{"0x1cf5cd427d0a968379bd6b5befce28d8e157ae38":"22963773121","0x6f118ecebc31a5ffe49b87c47ea80f93a2af0a8a":"285685502528"} -> {"0x1cf5cd427d0a968379bd6b5befce28d8e157ae38":"19681121807","0x6f118ecebc31a5ffe49b87c47ea80f93a2af0a8a":"288968153842"}
Last modified 1mo ago