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42 lines
2.6 KiB
42 lines
2.6 KiB
Application Architecture Guide
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==============================
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Here we provide a brief guide on the recommended architecture of a Tendermint blockchain
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application.
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The following diagram provides a superb example:
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https://drive.google.com/open?id=1yR2XpRi9YCY9H9uMfcw8-RMJpvDyvjz9
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The end-user application here is the Cosmos Voyager, at the bottom left.
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Voyager communicates with a REST API exposed by a local Light-Client Daemon.
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The Light-Client Daemon is an application specific program that communicates with
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Tendermint nodes and verifies Tendermint light-client proofs through the Tendermint Core RPC.
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The Tendermint Core process communicates with a local ABCI application, where the
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user query or transaction is actually processed.
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The ABCI application must be a deterministic result of the Tendermint consensus - any external influence
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on the application state that didn't come through Tendermint could cause a
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consensus failure. Thus *nothing* should communicate with the application except Tendermint via ABCI.
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If the application is written in Go, it can be compiled into the Tendermint binary.
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Otherwise, it should use a unix socket to communicate with Tendermint.
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If it's necessary to use TCP, extra care must be taken to encrypt and authenticate the connection.
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All reads from the app happen through the Tendermint `/abci_query` endpoint.
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All writes to the app happen through the Tendermint `/broadcast_tx_*` endpoints.
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The Light-Client Daemon is what provides light clients (end users) with nearly all the security of a full node.
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It formats and broadcasts transactions, and verifies proofs of queries and transaction results.
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Note that it need not be a daemon - the Light-Client logic could instead be implemented in the same process as the end-user application.
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Note for those ABCI applications with weaker security requirements, the functionality of the Light-Client Daemon can be moved
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into the ABCI application process itself. That said, exposing the application process to anything besides Tendermint over ABCI
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requires extreme caution, as all transactions, and possibly all queries, should still pass through Tendermint.
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See the following for more extensive documentation:
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- [Interchain Standard for the Light-Client REST API](https://github.com/cosmos/cosmos-sdk/pull/1028)
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- [Tendermint RPC Docs](https://tendermint.github.io/slate/)
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- [Tendermint in Production](https://github.com/tendermint/tendermint/pull/1618)
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- [Tendermint Basics](https://tendermint.readthedocs.io/en/master/using-tendermint.html)
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- [ABCI spec](https://github.com/tendermint/abci/blob/master/specification.rst)
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