d7606777cf
This is a very small change, but removes a method from the `service.Service` interface (a win!) and forces callers to explicitly pass loggers in to objects during construction rather than (later) injecting them. There's not a real need for this kind of lazy construction of loggers, and I think a decent potential for confusion for mutable loggers. The main concern I have is that this changes the constructor API for ABCI clients. I think this is fine, and I suspect that as we plumb contexts through, and make changes to the RPC services there'll be a number of similar sorts of changes to various (quasi) public interfaces, which I think we should welcome.
KVStore
There are two app's here: the KVStoreApplication and the PersistentKVStoreApplication.
KVStoreApplication
The KVStoreApplication is a simple merkle key-value store.
Transactions of the form key=value are stored as key-value pairs in the tree.
Transactions without an = sign set the value to the key.
The app has no replay protection (other than what the mempool provides).
PersistentKVStoreApplication
The PersistentKVStoreApplication wraps the KVStoreApplication and provides two additional features:
- persistence of state across app restarts (using Tendermint's ABCI-Handshake mechanism)
- validator set changes
The state is persisted in leveldb along with the last block committed, and the Handshake allows any necessary blocks to be replayed. Validator set changes are effected using the following transaction format:
"val:pubkey1!power1,pubkey2!power2,pubkey3!power3"
where pubkeyN is a base64-encoded 32-byte ed25519 key and powerN is a new voting power for the validator with pubkeyN (possibly a new one).
To remove a validator from the validator set, set power to 0.
There is no sybil protection against new validators joining.