Implements a PostgreSQL logical replication module that streams WAL
changes, buffers them per XID for transaction atomicity, and publishes
CacheKey invalidation events to the existing framework broadcast channel.
Key design choices:
- Transaction atomicity: changes are buffered until COMMIT so the fanout
always receives a consistent view. A 1000-row bulk-insert emits one
table-level CacheKey, not 1000 row events.
- Native protocol: uses a self-contained raw TCP + postgres-protocol
implementation for the replication connection (tokio-postgres 0.7 does
not expose copy_both_simple publicly).
- Corrected pgoutput v1 parser: original maybe_sql_integration code
incorrectly read XID from DML messages; DML messages carry no XID in
proto v1 — only Begin does.
- Clean integration: publishes CacheKey::Channel events to store.events
so the existing fanout task picks them up with zero changes to the
fanout loop.
- New cx.subscribe(key) API on RenderContext for manually registering
subscription keys (needed when queries go through PgPool, not cx.run).
New files:
src/pg_replication/mod.rs — PgReplicationListener, key helpers
src/pg_replication/wal_parser.rs — pgoutput v1 binary protocol parser
src/pg_replication/emitter.rs — WalEmitter (tx-buffering + CacheKey emit)
src/pg_replication/proto.rs — raw TCP PG wire-protocol connection
examples/pg_replication/main.rs — live message board example
docker-compose.yml — PG 16 container with wal_level=logical
Run the example:
docker compose up -d
cargo run --example pg_replication --features pg_replication
https://claude.ai/code/session_01SLGgXeqKV2o7KTmCaQZZPg
