segmented_wal.md

segmented wal

Language: Python · Sphere: programming · Category: Persistence

Signature: (wal: WriteAheadLog) → None

What it does

Write-Ahead Log (WAL) implementation for durable transaction logging.

This module provides a complete WAL system with:

• Append-only writes for durability
• Checksum verification for data integrity
• Segment-based log rotation
• Crash recovery and replay functionality

Guarantee

When it runs, segmented wal guarantees n_recovered == 15; len(wal.segments) >= 3; replayed == transactions (proven by run).

Checkable constraints:

• len(wal.segments) >= 3
• replayed == transactions
• replayed[7] == b'TX-007:' + b'x' * 60
• n_recovered == 15
• recovered[:12] == transactions
• recovered[12:] == [b'crash-1', b'crash-2', b'crash-3']
• 0 < len(survivors) < 15
• survivors == transactions[:len(survivors)]

Verification evidence

• Green-run: ✓ passes (re-run under the extractor's gate)
• Constraint strength: recovery (truth-pinned)
• Independent oracle: ✓ hard — chaos (validator v1.9)
• Peer review: unreviewed

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