Move signature verification out of the write transaction and parallelize it

[RickiNano]

Block signature verification currently runs serially inside the ledger write transaction: the block processor opens a write tx per batch and each ledger.process() call does its ed25519 checks while holding it. This PR moves that CPU work out of the transaction and onto a small worker pool, so batches are pre-validated in parallel before the write tx is opened.

Benefits

• Higher block throughput. Serial signature work now spread across up to 4 threads
• Shorter write transaction hold times. The write tx now spends its time on actual store reads/writes instead of signature validation
• Zero behavioral change. Results are bit-identical to today: same checks, same order of ledger application, same result codes, same notification order. A duplicate block with a bad signature still returns old, forks and rollbacks are untouched.

How it works

• block_context gains a nano::signature_verification result (unknown / valid / valid_epoch / invalid), defaulting to unknown.
• process_batch() fans the batch out across a dedicated nano::thread_pool between next_batch() and tx_begin_write(). Workers verify state blocks (against the account owner first, then the epoch signer for epoch links — the same order the ledger processor uses) and open blocks. Legacy send/receive/change blocks need a frontier lookup to determine the signer, so they stay unknown and are verified inline as today; they are effectively extinct on the live network.
• ledger.process() accepts the verification result (defaulting to unknown, so all existing callers keep today's behavior). Inside ledger_processor, a new validate_signature() helper consumes the pre-computed result where it is conclusive and falls back to validate_message() where it isn't. Debug builds re-verify every skipped check via debug_assert.
• Pre-verified invalid blocks are still rejected at the existing check site inside the transaction (not short-circuited earlier), preserving today's result-code precedence.

Co-authored with Claude Fable

[gr0vity-dev-bot]

Test Results for Commit 8f2c2b4

Pull Request 5103: Results
Overall Status: ✅

Test Case Results

• ✅ 5n4pr_conf_10k_bintree: PASS (Duration: 111s)
• ✅ 5n4pr_conf_10k_change: PASS (Duration: 134s)
• ✅ 5n4pr_conf_change_dependant: PASS (Duration: 114s)
• ✅ 5n4pr_conf_change_independant: PASS (Duration: 117s)
• ✅ 5n4pr_conf_send_dependant: PASS (Duration: 106s)
• ✅ 5n4pr_conf_send_independant: PASS (Duration: 144s)
• ✅ 5n4pr_rocks_10k_bintree: PASS (Duration: 112s)
• ✅ 5n4pr_rocks_10k_change: PASS (Duration: 186s)

Last updated: 2026-07-09 23:23:52 UTC

[Copilot]

Pull request overview

This PR reduces ledger write-transaction hold time by pre-validating block signatures outside the transaction and (for eligible block types) doing that work in parallel, then threading the pre-validation result into ledger.process()/ledger_processor so the in-tx signature check can be skipped when conclusive.

Changes:

• Add nano::signature_verification and plumb it through ledger::process() into ledger_processor.
• Add a configurable verification worker pool to block_processor to pre-validate signatures for each batch before opening the write transaction.
• Add config + stats + TOML coverage for the new verification_threads setting and blocks_verified stat.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
nano/secure/ledger.hpp	Extends ledger::process() API to accept optional pre-validation result.
nano/secure/ledger.cpp	Passes pre-validation result into ledger_processor.
nano/secure/ledger_processor.hpp	Extends ledger_processor to store a pre-validation result and adds validate_signature() helper.
nano/secure/ledger_processor.cpp	Implements validate_signature() and routes relevant signature checks through it.
nano/secure/common.hpp	Introduces signature_verification enum used for pre-validation.
nano/node/block_processor.hpp	Adds verification_threads config and declares batch verification helpers/pool.
nano/node/block_processor.cpp	Implements parallel batch signature verification, config serialization, and stats reporting.
nano/node/block_context.hpp	Stores per-block pre-validation result in block_context.
nano/lib/stats_enums.hpp	Adds blocks_verified stat detail.
nano/core_test/toml.cpp	Extends TOML config tests to include verification_threads.

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[RickiNano]

I need to rebase this branch on develop to fix the conflicts

[RickiNano]

Rebased and ready for review @pwojcikdev