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src/kernel/mempoolentry.h

CategoryDeveloper / Source AtlasStatusReviewed / Source-confirmed structuralLast reviewed2026-09-12

Purpose

Section titled “Purpose”

src/kernel/mempool_entry.h defines the per-transaction metadata stored by BitcoinII Core’s mempool, principally through CTxMemPoolEntry.

The reviewed v31.1.0 structure remains broadly Bitcoin-style. BitcoinII-specific replay-protection behavior is applied during admission/script validation and cache separation rather than by adding a replay-domain field to CTxMemPoolEntry itself.

What an entry tracks

Section titled “What an entry tracks”

Reviewed entry state includes:

  • transaction reference;
  • direct mempool parents/children;
  • original and modified fee;
  • transaction weight and memory usage;
  • local entry time and chain height at admission;
  • whether the transaction spends coinbase output;
  • signature-operation cost;
  • cached sequence-lock LockPoints;
  • ancestor/descendant counts, sizes, and modified-fee totals;
  • entry sequence / relay-recency state.

These cached values support policy, mining/template selection, graph operations, replacement/eviction behavior, and reorg repair.

LockPoints

Section titled “LockPoints”

LockPoints caches height, MedianTimePast-related time, and the highest relevant input block used for relative-locktime evaluation.

After a reorg, cached lock points can remain usable only when the new active chain still has the relevant ancestry; otherwise higher-level mempool/reorg logic repairs or removes affected entries.

Ancestor/descendant accounting

Section titled “Ancestor/descendant accounting”

CTxMemPoolEntry caches package-level state used by ancestor-aware policy and mining selection.

This is relevant to current block-template assembly, which still uses ancestor-aware package scoring in the reviewed v31 path. ShockWave changes required block work, not this per-entry fee/graph data structure.

See Block-template assembly.

Modified fee and local policy

Section titled “Modified fee and local policy”

The entry keeps original fee and a local modified-fee value used by prioritization/template policy. Local fee deltas do not rewrite the transaction or alter BitcoinII consensus validity.

Notification helper structs

Section titled “Notification helper structs”

The header also defines transaction-info structures used for mempool notifications/removals/additions, carrying fields such as transaction reference, fee, virtual size, admission height, and package/current-chain-state context.

v31 replay boundary

Section titled “v31 replay boundary”

Mempool admission on current BitcoinII validates signatures for the next block’s replay domain and clears legacy-domain state at the activation boundary. Validation-cache keys are also separated by fork id.

Those behaviors live in the surrounding validation/script paths. A CTxMemPoolEntry existing in memory should therefore be understood as state produced after the relevant admission checks, not as the implementation of replay protection itself.

See Mempool accept and Replay protection v31.

Runtime boundary

Section titled “Runtime boundary”

The September 11 isolated v31.1.0 regtest PSBT test successfully inserted a disposable signed transaction into the local mempool and confirmed it with getmempoolentry.

That runtime result corroborates ordinary current-release entry creation/inspection in the documented zero-peer environment. It did not instrument every internal field or the mainnet replay activation transition.

Section titled “Related pages”

Open work

Section titled “Open work”
  • Map replacement/eviction and fee-estimator consumers in more detail if operator guidance needs them.
  • Build a deterministic package fixture if ancestor/descendant behavior needs direct runtime examples.
  • Keep the current regtest mempool observation distinct from mainnet replay-boundary testing.

Primary sources

Section titled “Primary sources”
  • v31.1.0/src/kernel/mempool_entry.h
  • v31.1.0/src/txmempool.h
  • v31.1.0/src/txmempool.cpp
  • v31.1.0/src/validation.cpp

Canonical tag: https://github.com/Bitcoin-II/BitcoinII-Core/tree/v31.1.0

Verification

Section titled “Verification”

Status: Reviewed / Source-confirmed structural
Primary evidence: BitcoinII Core v31.1.0 mempool entry/source review plus September 11 local-mempool runtime evidence
Notes: Entry structure is current and ordinary entry creation was runtime-corroborated. Full internal-field instrumentation, package/replacement tests, and mainnet replay-boundary behavior remain separate work.