github.com/fiagdao/tendermint@v0.32.11-0.20220824195748-2087fcc480c1/docs/app-dev/app-architecture.md (about) 1 --- 2 order: 3 3 --- 4 5 # Application Architecture Guide 6 7 Here we provide a brief guide on the recommended architecture of a 8 Tendermint blockchain application. 9 10 The following diagram provides a superb example: 11 12 ![](../imgs/cosmos-tendermint-stack-4k.jpg) 13 14 We distinguish here between two forms of "application". The first is the 15 end-user application, like a desktop-based wallet app that a user downloads, 16 which is where the user actually interacts with the system. The other is the 17 ABCI application, which is the logic that actually runs on the blockchain. 18 Transactions sent by an end-user application are ultimately processed by the ABCI 19 application after being committed by the Tendermint consensus. 20 21 The end-user application in this diagram is the Cosmos Voyager, at the bottom 22 left. Voyager communicates with a REST API exposed by a local Light-Client 23 Daemon. The Light-Client Daemon is an application specific program that 24 communicates with Tendermint nodes and verifies Tendermint light-client proofs 25 through the Tendermint Core RPC. The Tendermint Core process communicates with 26 a local ABCI application, where the user query or transaction is actually 27 processed. 28 29 The ABCI application must be a deterministic result of the Tendermint 30 consensus - any external influence on the application state that didn't 31 come through Tendermint could cause a consensus failure. Thus _nothing_ 32 should communicate with the ABCI application except Tendermint via ABCI. 33 34 If the ABCI application is written in Go, it can be compiled into the 35 Tendermint binary. Otherwise, it should use a unix socket to communicate 36 with Tendermint. If it's necessary to use TCP, extra care must be taken 37 to encrypt and authenticate the connection. 38 39 All reads from the ABCI application happen through the Tendermint `/abci_query` 40 endpoint. All writes to the ABCI application happen through the Tendermint 41 `/broadcast_tx_*` endpoints. 42 43 The Light-Client Daemon is what provides light clients (end users) with 44 nearly all the security of a full node. It formats and broadcasts 45 transactions, and verifies proofs of queries and transaction results. 46 Note that it need not be a daemon - the Light-Client logic could instead 47 be implemented in the same process as the end-user application. 48 49 Note for those ABCI applications with weaker security requirements, the 50 functionality of the Light-Client Daemon can be moved into the ABCI 51 application process itself. That said, exposing the ABCI application process 52 to anything besides Tendermint over ABCI requires extreme caution, as 53 all transactions, and possibly all queries, should still pass through 54 Tendermint. 55 56 See the following for more extensive documentation: 57 58 - [Interchain Standard for the Light-Client REST API](https://github.com/cosmos/cosmos-sdk/pull/1028) 59 - [Tendermint RPC Docs](https://docs.tendermint.com/master/rpc/) 60 - [Tendermint in Production](../tendermint-core/running-in-production.md) 61 - [ABCI spec](https://github.com/tendermint/spec/tree/95cf253b6df623066ff7cd4074a94e7a3f147c7a/spec/abci)