Federico Kunze Küllmer f7bcc8d12e

* docs: update

* update +

* txs

* update docs

* more docs

* spec update

* doc fixes

2021-08-03 17:35:31 +00:00

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Concepts

EVM

The Ethereum Virtual Machine EVM is a state machine that provides the necessary tools to run or create a contract on a given state.

State DB

The StateDB interface from geth represents an EVM database for full state querying of both contracts and accounts. The concrete type that fulfills this interface on Ethermint is the CommitStateDB.

Genesis State

The x/evm module GenesisState defines the state necessary for initializing the chain from a previous exported height.

+++ https://github.com/tharsis/ethermint/blob/v0.3.1/x/evm/types/genesis.go#L14-L20

Genesis Accounts

The GenesisAccount type corresponds to an adaptation of the Ethereum GenesisAccount type. Its main difference is that the one on Ethermint uses a custom Storage type that uses a slice instead of maps for the evm State (due to non-determinism), and that it doesn't contain the private key field.

It is also important to note that since the auth and bank SDK modules manage the accounts and balance state, the Address must correspond to an EthAccount that is stored in the auth's module AccountKeeper and the balance must match the balance of the EvmDenom token denomination defined on the GenesisState's Param. The values for the address and the balance amount maintain the same format as the ones from the SDK to make manual inspections easier on the genesis.json.

+++ https://github.com/tharsis/ethermint/blob/v0.3.1/x/evm/types/genesis.go#L22-L30

Transaction Logs

On every Ethermint transaction, its result contains the Ethereum Logs from the state machine execution that are used by the JSON-RPC Web3 server for for filter querying. Since Cosmos upgrades don't persist the transactions on the blockchain state, we need to persist the logs the EVM module state to prevent the queries from failing.

TxsLogs is the field that contains all the transaction logs that need to be persisted after an upgrade. It uses an array instead of a map to ensure determinism on the iteration.

+++ https://github.com/tharsis/ethermint/blob/v0.3.1/x/evm/types/logs.go#L12-L18

Chain Config

The ChainConfig is a custom type that contains the same fields as the go-ethereum ChainConfig parameters, but using sdk.Int types instead of *big.Int. It also defines additional YAML tags for pretty printing.

The ChainConfig type is not a configurable SDK Param since the SDK does not allow for validation against a previous stored parameter values or Context fields. Since most of this type's fields rely on the block height value, this limitation prevents the validation of of potential new parameter values against the current block height (eg: to prevent updating the config block values to a past block).

If you want to update the config values, use an software upgrade procedure.

+++ https://github.com/tharsis/ethermint/blob/v0.3.1/x/evm/types/chain_config.go#L16-L45

Params

See the params document for further information about parameters.

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