all: move main transaction pool into a subpool #27463

[gzliudan]

Proposed changes

Ref: ethereum#27463

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)
• Regular KTLO or any of the maintaince work. e.g code style
• CICD Improvement

Impacted Components

Which part of the codebase this PR will touch base on,

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• Consensus
• Account
• Network
• Geth
• Smart Contract
• External components
• Not sure (Please specify below)

Checklist

Put an ✅ in the boxes once you have confirmed below actions (or provide reasons on not doing so) that

• This PR has sufficient test coverage (unit/integration test) OR I have provided reason in the PR description for not having test coverage
• Provide an end-to-end test plan in the PR description on how to manually test it on the devnet/testnet.
• Tested the backwards compatibility.
• Tested with XDC nodes running this version co-exist with those running the previous version.
• Relevant documentation has been updated as part of this PR
• N/A

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[Copilot]

Pull request overview

This pull request implements a major architectural refactoring to move the main transaction pool into a subpool system, supporting specialization and modularity in transaction handling.

Summary: The PR restructures the transaction pool to use a coordinator pattern where a main TxPool manages multiple specialized SubPool implementations. The legacy transaction pool logic is moved to core/txpool/legacypool/, and a new wrapper type txpool.Transaction is introduced for better encapsulation.

Key Changes:

• Introduced subpool architecture with SubPool interface and main TxPool coordinator
• Moved legacy pool implementation to dedicated legacypool package
• Added transaction wrapper type (txpool.Transaction) for better type safety
• Updated API signatures across the codebase (e.g., AddLocal → Add, Stop() → Close())

Reviewed changes

Copilot reviewed 37 out of 37 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
core/txpool/txpool.go	New main transaction pool coordinator implementing subpool aggregation
core/txpool/subpool.go	Defines SubPool interface for specialized transaction pools
core/txpool/legacypool/legacypool.go	Refactored legacy pool as a SubPool implementation
core/txpool/errors.go	Centralized error definitions for transaction pool
event/multisub.go	New utility for joining multiple event subscriptions
eth/backend.go	Updated to use new pool initialization pattern
miner/worker.go	Type signature updates for transaction maps
internal/ethapi/backend.go	Interface signature updates for consistency
eth/protocol.go	Updated txPool interface with new method signatures
Multiple test files	Updated tests to use new API (e.g., addLocal, addRemote, Close)

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[Copilot]

Pull request overview

Copilot reviewed 37 out of 37 changed files in this pull request and generated 4 comments.

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[Copilot]

Pull request overview

Copilot reviewed 37 out of 37 changed files in this pull request and generated no new comments.

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[Copilot]

Pull request overview

Copilot reviewed 38 out of 38 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (2)

miner/worker.go:1

• The condition on line 993 has been modified to use addition instead of subtraction, which reverses the comparison logic. The original condition checked blkNumber <= w.header.Number.Uint64()-w.config.XDPoS.Epoch*2, but the new condition blkNumber+w.config.XDPoS.Epoch*2 <= w.header.Number.Uint64() is mathematically equivalent only when no overflow occurs. However, if blkNumber + w.config.XDPoS.Epoch*2 overflows uint64, this could lead to incorrect validation. Consider adding overflow protection or reverting to the original subtraction-based logic with a guard against underflow.
  miner/worker.go:1
• The byte slice extraction has changed from data[8:40] to data[4:36], altering which 32 bytes are interpreted as the block number. This is a breaking change in the data structure interpretation. Ensure this change aligns with updates to the data format specification, as existing transactions may be parsed incorrectly.

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