Journal

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Overview

The journal records all execution steps.

It is an append-only log.

Purpose

Journal enables:

  • replay
  • debugging
  • recovery

Entry Structure

Each entry records:

  • selected message
  • transition executed
  • state changes

Append Model

J = e1, e2, e3, ...

Replay

State reconstruction:

state = replay(initial_state, journal)

Durability

Journal must:

  • be written atomically
  • survive crashes

Determinism

Replay must produce:

  • identical state
  • identical execution trace