B6 · Putting It All Together
Four systems, one stack.
The course’s four libraries compose into one dependency-ordered umbrella, wire ← data ← mq ← store, booting only after the identity contract proves itself. Then a write goes all the way down, and a read all the way up.
Three dives. The umbrella and its boot; one write down through the outbox, a lane, and a flow; one read up the four-tier ladder, kept current by coherence.
The three dives
each a leaf, the teachingOne umbrella, four systems
echo_wire ← echo_data ← echo_mq ← echo_store: a dependency-closed tree that boots only after the contract self-check passes.
One write, all the way down
A store write fans out through a transactional outbox — record, enqueue on a lane, mark — rides an atomic Flow, and ends durable and announced.
B6.3One read, all the way up
A caller-side L1 hit, or a miss filling down through Valkey, the store, and the floor — ETS to Tigris, one id keying every tier.
A chapter is three dives. Each dive is one idea with one figure you can take apart.
The whole, in one law
echo · the umbrellaB6 puts the course together: the four libraries — echo_wire, echo_data, echo_mq, echo_store — compose into one dependency-ordered umbrella, wire ← data ← mq ← store, that boots only after the identity contract proves itself. A write begins at a system’s store and fans out through a transactional outbox: record the intent, enqueue on a lane, mark it enqueued, with replay covering every crash window; multi-step work rides an atomic Flow, settlement rides a lane, and the write ends durable on the floor and announced by coherence. A read climbs the same stack in reverse — a caller-side L1 hit, or a miss filling down through Valkey, the store, and the floor — ETS to Tigris, one branded id keying every tier. The pieces are not merged; they are composed, fast at the top and durable at the bottom.
The doors
the sibling coursesEchoMQ — the protocol, in depth
The bus B3 narrates, taught rung by rung: the keyspace, the Lua inventory, and the 3.0 Stream Tier — XADD, XREADGROUP, XACK — with conformance on Valkey.
Redis Patterns Applied
The substrate patterns under the bus: sorted sets, atomic Lua moves, locks, and streams — the judgement layer.
/echo-persistenceEcho Persistence — the durable floor
Beneath the volatile tiers: the Graft page engine built twice, the commit-LSN loop, and the stream archive on Tigris. Where Part I says state lives somewhere, this says where it lives durably.
References
sources · relatedSources
- Erlang/OTP — the supervisor behaviourthe dependency-ordered tree the umbrella boots
- Helland — Life Beyond Distributed Transactions (CIDR 2007)the outbox of activities that makes a multi-step write recoverable
- Erlang/OTP — the ets modulethe L1 table a read hits caller-side before any tier beneath
Related
- BCS — the course homethe law, the id anatomy, the chapter map
- Echo Persistencethe durable floor beneath the bus