Mukan Erkin Törük
ef24c0b67e
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41 lines
2 KiB
Markdown
41 lines
2 KiB
Markdown
---
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order: 1
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parent:
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title: ABCI++
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order: 3
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---
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# ABCI++
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## Introduction
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ABCI++ is a major evolution of ABCI (**A**pplication **B**lock**c**hain **I**nterface).
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Like its predecessor, ABCI++ is the interface between CometBFT (a state-machine
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replication engine) and the actual state machine being replicated (i.e., the Application).
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The API consists of a set of _methods_, each with a corresponding `Request` and `Response`
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message type.
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The methods are always initiated by CometBFT. The Application implements its logic
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for handling all ABCI++ methods.
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Thus, CometBFT always sends the `Request*` messages and receives the `Response*` messages
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in return.
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All ABCI++ messages and methods are defined in [protocol buffers](https://github.com/cometbft/cometbft/blob/v0.38.x/proto/tendermint/abci/types.proto).
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This allows CometBFT to run with applications written in many programming languages.
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This specification is split as follows:
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- [Overview and basic concepts](./abci++_basic_concepts.md) - interface's overview and concepts
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needed to understand other parts of this specification.
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- [Methods](./abci++_methods.md) - complete details on all ABCI++ methods
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and message types.
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- [Requirements for the Application](./abci++_app_requirements.md) - formal requirements
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on the Application's logic to ensure CometBFT properties such as liveness. These requirements define what
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CometBFT expects from the Application; second part on managing ABCI application state and related topics.
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- [CometBFT's expected behavior](./abci++_comet_expected_behavior.md) - specification of
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how the different ABCI++ methods may be called by CometBFT. This explains what the Application
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is to expect from CometBFT.
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- [Example scenarios](./abci++_example_scenarios.md) - specific scenarios showing why the Application needs to account
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for any CometBFT's behaviour prescribed by the specification.
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- [Client and Server](./abci++_client_server.md) - for those looking to implement their
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own ABCI application servers.
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