diff --git a/docs/architecture/adr-038-deliver-block.md b/docs/architecture/adr-038-deliver-block.md new file mode 100644 index 000000000..ac23ab693 --- /dev/null +++ b/docs/architecture/adr-038-deliver-block.md @@ -0,0 +1,100 @@ +# ADR 037: Deliver Block + +Author: Daniil Lashin (@danil-lashin) + +## Changelog + +13-03-2019: Initial draft + +## Context + +Initial conversation: https://github.com/tendermint/tendermint/issues/2901 + +Some applications can handle transactions in parallel, or at least some +part of tx processing can be parallelized. Now it is not possible for developer +to execute txs in parallel because Tendermint delivers them consequentially. + +## Decision + +Now Tendermint have `BeginBlock`, `EndBlock`, `Commit`, `DeliverTx` steps +while executing block. This doc proposes merging this steps into one `DeliverBlock` +step. It will allow developers of applications to decide how they want to +execute transactions (in parallel or consequentially). Also it will simplify and +speed up communications between application and Tendermint. + +As @jaekwon [mentioned](https://github.com/tendermint/tendermint/issues/2901#issuecomment-477746128) +in discussion not all application will benefit from this solution. In some cases, +when application handles transaction consequentially, it way slow down the blockchain, +because it need to wait until full block is transmitted to application to start +processing it. Also, in the case of complete change of ABCI, we need to force all the apps +to change their implementation completely. That's why I propose to introduce one more ABCI +type. + +# Implementation Changes + +In addition to default application interface which now have this structure + +```go +type Application interface { + // Info and Mempool methods... + + // Consensus Connection + InitChain(RequestInitChain) ResponseInitChain // Initialize blockchain with validators and other info from TendermintCore + BeginBlock(RequestBeginBlock) ResponseBeginBlock // Signals the beginning of a block + DeliverTx(tx []byte) ResponseDeliverTx // Deliver a tx for full processing + EndBlock(RequestEndBlock) ResponseEndBlock // Signals the end of a block, returns changes to the validator set + Commit() ResponseCommit // Commit the state and return the application Merkle root hash +} +``` + +this doc proposes to add one more: + +```go +type Application interface { + // Info and Mempool methods... + + // Consensus Connection + InitChain(RequestInitChain) ResponseInitChain // Initialize blockchain with validators and other info from TendermintCore + DeliverBlock(RequestDeliverBlock) ResponseDeliverBlock // Deliver full block + Commit() ResponseCommit // Commit the state and return the application Merkle root hash +} + +type RequestDeliverBlock struct { + Hash []byte + Header Header + Txs Txs + LastCommitInfo LastCommitInfo + ByzantineValidators []Evidence +} + +type ResponseDeliverBlock struct { + ValidatorUpdates []ValidatorUpdate + ConsensusParamUpdates *ConsensusParams + Tags []common.KVPair + TxResults []ResponseDeliverTx +} + +``` + +Also, we will need to add new config param, which will specify what kind of ABCI application uses. +For example, it can be `abci_type`. Then we will have 2 types: +- `advanced` - current ABCI +- `simple` - proposed implementation + +## Status + +In review + +## Consequences + +### Positive + +- much simpler introduction and tutorials for new developers (instead of implementing 5 methods whey +will need to implement only 3) +- txs can be handled in parallel +- simpler interface +- faster communications between Tendermint and application + +### Negative + +- Tendermint should now support 2 kinds of ABCI