Uniswap V3 Bot — Bugfixes (Part V)

Squish!

This is a short post detailing two bug fixes for the Uniswap V3 bot.

I will release periodic posts like this as I identify and fix bugs. Thank you for reporting issues!

Flashbots Middleware Fix

This is a frustrating one but is important to share. The bot uses the web3-flashbots middleware to perform simulation and send bundles to the relay.

The newest version (v1.1.0) has a bug that throws an exception when the send_bundle method is called with the optional opts argument omitted. It’s optional so the middleware is expected to perform correctly, but it does not.

I’ve isolated the cause of the error and posted an issue on their github which you can follow if interested.

Workaround

Until they fix this issue, the workaround is to adjust all calls to send_bundle to include a dictionary. This dictionary can have values if you are using these optional arguments, or empty if you are not.

For example, change this:

w3.flashbots.send_bundle(
    bundle,
    target_block_number=target_block + i,
)

to this:

w3.flashbots.send_bundle(
    bundle,
    target_block_number=target_block + i,
    opts={},
)

Version Note

This regression was introduced in the new release (v1.1.0). You do not need to apply this workaround if you are using the older version.

I will post an update when the fix is implemented in the official version.

Tick Bitmap Fixes

I’ve isolated two bugs in the V3 helper that were affecting tick bitmaps.

Tick Range Gap

This bug would generate exceptions about lower_word being unreferenced. This occurred because I made a bad assumption in my pre-calculation checks that a requested tick word would never be generated within the existing range of known words. It turns out that the behavior of the external_update method was affecting this assumption. If external_update attempts to update the liquidity at an unknown tick, it will fetch that single tick before proceeding. This can leave a “gap” in the known tick range, which invalidated my assumption. The helper now behaves correctly.

Out-of-Order Check

I defined the known tick word range with two variables (min_word and max_word). Unfortunately I did this after using it in a pre-calculation check, which threw exceptions about an unreferenced variable.

The fix was simple: flip the position of those two code blocks. You can see that commit HERE.

Fixes

Pull the latest version of degenbot from github to apply these fixes.