Applied state, durable progress and roots

Applied state, durable progress and roots A data-flow diagram generated by Archify. 01 / Speculate 02 / Apply 03 / Queue 04 / Durability barrier 05 / Persistent state Transaction journal · pending writes + deletes · 01 / Speculate Transaction journal pending writes + deletes Common commit · locked, sorted batch · 02 / Apply Common commit locked, sorted batch Hot account view · execution reads · 02 / Apply Hot account view execution reads Cumulative root · reporter diff history · 02 / Apply Cumulative root reporter diff history Ordered writer · 16-batch bounded queue · 03 / Queue Ordered writer 16-batch bounded queue WAL, then height · ordered disk barrier · 04 / Durability barrier WAL, then height ordered disk barrier QMDB drain · applied marker + root · 05 / Persistent state QMDB drain applied marker + root changeset apply enqueue ordered diffs persist forward

A write failure halts further progress

  • • The writer appends WAL, publishes durable height, then forwards the batch. Later commits refuse a halted writer.

Always compare the same root at the same height

  • • The reporter cumulative root is separate from the QMDB root. Executed state can lead the durable recovery point.