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Streams listed in Options.Streams are created by Start() when the embedded NATS server initializes, replacing manual EnsureStream calls during setup. Migrates nats-chatroom and pubsub-crud examples.
3.3 KiB
3.3 KiB
NATS Chatroom Example (Embedded)
A chatroom built with Via and an embedded NATS server, demonstrating pub/sub messaging as an alternative to the custom Rooms implementation in ../chatroom.
Via includes an embedded NATS server that starts automatically — no external server required.
Key Differences from Original Chatroom
| Aspect | Original (../chatroom) |
This Example |
|---|---|---|
| Pub/sub | Custom Rooms struct (~160 lines) |
NATS subjects |
| Member tracking | Manual map[TU]Syncable |
NATS handles subscribers |
| Publish timing | Ticker every 100ms + dirty flag | Instant delivery |
| Durability | None (in-memory) | JetStream persists to disk |
| Multi-instance | Not supported | Works across server instances |
| External deps | None | None (NATS embedded in binary) |
Run the Example
go run ./internal/examples/nats-chatroom
That's it. No separate NATS server needed.
Open multiple browser tabs at http://localhost:7331 to see messages broadcast across all clients.
Architecture
┌─────────────────────────────────────────────────────────┐
│ Single Binary │
│ │
│ Browser A Embedded NATS Browser B │
│ │ │ │ │
│ │-- Via Action ---> │ │ │
│ │ (Send msg) │ │ │
│ │ │ │ │
│ │ nc.Publish() │ │
│ │ "chat.room.Go" │ │
│ │ │ │ │
│ │<-- Subscribe -----|---- Subscribe --->│ │
│ │ callback │ callback │ │
│ │ │ │ │
│ │-- c.Sync() ------>│<--- c.Sync() -----| │
│ │ (SSE) │ (SSE) │ │
│ │
└─────────────────────────────────────────────────────────┘
JetStream Durability
Messages persist to disk via JetStream. Streams are declared in Options.Streams and created automatically when v.Start() initializes the embedded NATS server:
v.Config(via.Options{
Streams: []via.StreamConfig{{
Name: "CHAT",
Subjects: []string{"chat.>"},
MaxMsgs: 1000,
MaxAge: 24 * time.Hour,
}},
})
Stop and restart the app - chat history survives.
Code Comparison
Original chatroom - 160+ lines of custom pub/sub:
Roomsstruct with named roomsRoomwith member tracking, mutex, dirty flag- Ticker-based publish loop
- Manual join/leave channels
This example - ~60 lines of NATS integration:
via.Subscribe(c, subject, handler)for receivingvia.Publish(c, subject, data)for sending- Streams declared in
Options— NATS handles delivery, no polling