Chapter 21 — Single-Producer Ring, Journal + Business-Logic Pipeline
A sequence barrier expresses fan-out and staged dependencies with nothing but atomic loads and comparisons, because every mutable position in the system has exactly one writer.
The full source for this example lives in
examples/concurrency/21-lock-free-messaging-and-the-disruptor/— clone the repo,cdin, and./demo.sh.
Chapter reference: Doc 21 — Lock-Free Messaging and the Disruptor
What it shows
One producer publishes slots on a fixed-capacity ring; a journal consumer trails the published sequence and naturally batches under load; a deliberately slowed business-logic consumer trails the journal’s sequence rather than the producer’s directly — the diamond-dependency sequence barrier that lets the dependent stage never see an event the journal hasn’t already processed. Every published event being consumed exactly once, in order, by both stages, the dependent stage never reading past the journal’s own sequence, and the producer actually backing off at least once are all checked as hard assertions, since the business stage’s fixed slowdown makes back-pressure a deterministic property of the run rather than a race against host speed. Throughput is reported, not asserted, since it depends on host core count and placement.
Running it
cd examples/concurrency/21-lock-free-messaging-and-the-disruptor
./demo.sh # build + run disruptor_ring + verify.lua
./demo.sh --clean # remove the image