Forking Brilliant

Houston We Have A Problem

I want to check that a transaction will work on mainnet for an account I don’t control. In this case it’s for a large LP in the Balancer staBal3 pool and I want to check they could successfully migrates their staBal3 to the new bb-a-USD using a Relayer multicall with the params created by the SDK.

This definitely isn’t the most elegant way of doing things but it works!

Whale Hunting

The first thing I need to do is to find a large staBal3 LP account and figure out their BPT balance. I can use the Balancer Subgraph to query account pool shares for the staBal3 pool. Query looks like:

query MyQuery {
  poolShares(where: {poolId: "0x06df3b2bbb68adc8b0e302443692037ed9f91b42000000000000000000000063"}, orderBy: balance, orderDirection: desc) {

I then manually worked my way down the list of addresses until I found one that was an EOA: and at the time of investiagation this had a BPT balance of: 10205792.037653741889318463 (a cool $10.28mil!).

Exit Stage Right

The SDK helper function (relayer.exitPoolAndBatchSwap) that creates the call data requires an input param of expectedAmountsOut which in this case represents the DAI/USDC/USDT amounts out when exiting the staBal3 pool. Because I don’t have the maths required for this exposed yet a quick way to get this is to see the output amounts using Withdraw in the UI. There’s a very nice tool that allows us to simulate this when we don’t have control of the account of interest:

Now that I’ve got all the info required I can generate the call data by using the helper function. In this case we get an array of call data which represent an exitPool call on staBal3 followed by a batchSwap that swaps the stables received from the exit to the bb-a-USD BPT.

The Magic

Tenderly has lots of useful features including Transaction Simulations. To begin I tried simulating the multicall call on the Mainnet Relayer but the tx failed highlighting a new issue – the account hasn’t approved the Balancer Relayer. To get around this I can use a Tenderly Fork – “Forks allow you to chain simulation and test out complex scenarios with live on-chain data”. This is cool because I can now fork the chain make an approval on the relayer from the account which then allows me to succesfully simulate the multicall!

Photo by Joel Muniz on Unsplash

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