Propose: remove packages XDCx, XDCxDAO, XDCxlending

[gzliudan]

Propose

Remove the following packages:

• XDCx
• XDCxDAO
• XDCxlending

Reason

• These packages have not been used by any user.
• The source code of these packages has not been upgraded for a long time. These outdated codes become obstacles in current development work.

How to handle the current data

These packages use a separate directory XDCx as data directory. While the other packages save data to the directory XDC. So I think is safe to remove these packages.

Work plan

Development

• remove packages
• fix other packages

Test plan

devnet

• sync devnet from genesis
• upgrade 1 node on devnet
• upgrade some nodes on devnet
• upgrade all nodes on devnet
• remove date directory XDCx after some days

testnet

• sync testnet from genesis
• upgrade 1 node on testnet
• upgrade some nodes on testnet
• upgrade all nodes on testnet
• remove date directory XDCx after some days

mainnet

• sync mainnet from genesis
• upgrade 1 node on mainnet
• upgrade some nodes on mainnet
• upgrade all nodes on mainnet
• remove date directory XDCx after some days

[mralj]

Hey! I might be missing something or misunderstanding the codebase, but I don't think you can entirely delete these packages (the code) because if you do, you won't be able to sync from Genesis anymore.

These packages use a separate directory XDCx as a data directory.

I assume when you say "data directory," you mean StateDB of the exchange/landing protocol(s) and the respective Merkle roots. The way I read the code, yes, they use a separate state (data directory), but as far as I can tell, these packages also mutate the main state (canonical blockchain state). Here is how:

1. In worker.go, we call XDCX.ProcessOrderPending (link), to which both work.state and work.tradingState are passed in. work.State is the main blockchain state.
2. This starts following call chain XDCx.CommitOrder (again with both states) > XDCx.ApplyOrder > Now there are a couple of calls which interact with the (main) stateDB, e.g., XDCx.processMarketOrder > XDCx.processOrderList > XDCx.getTradeQuantity
3. Which calls DoSettleBalance that mutates stateDB here and in e.g., SetTokenBalance calls

Given that XCDx/Landing protocols mutate the blockchain state, how will we sync from genesis once we remove this code?

cc @ak88

[gzliudan]

As you said, we need to carefully consider the side effects after removal. There are 2 solutions:

• only delete code unrelated to statedb
• if there are few XDCx transactions, we can hard code old block data for sync