3.2 KiB
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.
State Object
A stateObject represents an Ethereum account which is being modified.
The usage pattern is as follows:
- First you need to obtain a state object.
- Account values can be accessed and modified through the object.
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.