70 lines
3.0 KiB
Markdown
70 lines
3.0 KiB
Markdown
<!--
|
|
order: 1
|
|
-->
|
|
|
|
# Concepts
|
|
|
|
## EVM
|
|
|
|
The Ethereum Virtual Machine [EVM](https://ethereum.org/en/developers/docs/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 `Log`s 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](07_params.md) document for further information about parameters.
|