53 lines
3.1 KiB
Markdown
53 lines
3.1 KiB
Markdown
---
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title: Node architecture
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root: ..
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---
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## Node architecture
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Geth is an [execution client](https://ethereum.org/en/developers/docs/nodes-and-clients/#execution-clients).
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Originally, an execution client alone was enough to run a full Ethereum node.
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However, ever since Ethereum turned off [proof-of-work](https://ethereum.org/en/developers/docs/consensus-mechanisms/pow/) and implemented [proof-of-stake](https://ethereum.org/en/developers/docs/consensus-mechanisms/pow/),
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Geth has needed to be coupled to another piece of software called a
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[“consensus client”](https://ethereum.org/en/developers/docs/nodes-and-clients/#consensus-clients) in order to
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keep track of the Ethereum blockchain.
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The execution client is responsible for transaction handling, transaction gossip, state management and supporting
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the Ethereum Virtual Machine ([EVM])(https://ethereum.org/en/developers/docs/evm/). However, Geth is **not**
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responsible for block building, block gossiping or handling consensus logic. These are in the remit of the
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consensus client.
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The relationship between the two Ethereum clients is shown in the schematic below. The two clients each
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connect to their own respective peer-to-peer (P2P) networks. This is because the execution clients gossip
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transactions over their P2P network enabling them to manage their local transaction pool. The consensus clients
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gossip blocks over their P2P network, enabling consensus and chain growth.
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For this two-client structure to work, consensus clients must be able to pass bundles of transactions to
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Geth to be executed. Executing the transactions locally is how the client validates that the transactions
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do not violate any Ethereum rules and that the proposed update to Ethereum’s state is correct. Likewise,
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when the node is selected to be a block producer the consensus client must be able to request bundles of
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transactions from Geth to include in the new block. This inter-client communication is handled by a local
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RPC connection using the [engine API](https://github.com/ethereum/execution-apis/blob/main/src/engine/specification.md)
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which is exposed internally over port 8551 by default.
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## What does Geth do?
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As an execution client, Geth is responsible for creating the execution payloads - the bundles of transactions -
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that consensus clients include in their blocks. Geth is also responsible for re-executing transactions that arrive
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in new blocks to ensure they are valid. Executing transactions is done on Geth's embedded computer, known as the
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Ethereum Virtual Machine (EVM).
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Geth also offers a user-interface to Ethereum by exposing a set of RPC methods that enable users to query the
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Ethereum blockchain, submit transactions and deploy smart contracts using the command line, programmatically
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using Geth's built-in console, web3 development frameworks such as Hardhat and Truffle or via web-apps and wallets.
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In summary, Geth is:
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- a user gateway to Ethereum
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- home to the Ethereum Virtual Machine, Ethereum's state and transaction pool.
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Read more about [proof-of-stake](https://ethereum.org/en/developers/docs/consensus-mechanisms/pos/).
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