88bd0f31df
Demonstrates pub/sub messaging as an alternative to custom Rooms implementation. Uses delaneyj/toolbelt/embeddednats to run NATS with JetStream inside the binary - no external server required.
110 lines
3.8 KiB
Markdown
110 lines
3.8 KiB
Markdown
# NATS Chatroom Example (Embedded)
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A chatroom built with Via and an **embedded NATS server**, demonstrating pub/sub messaging as an alternative to the custom `Rooms` implementation in `../chatroom`.
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Uses `delaneyj/toolbelt/embeddednats` to run NATS inside the same binary - no external server required.
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## Key Differences from Original Chatroom
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| Aspect | Original (`../chatroom`) | This Example |
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|--------|-------------------------|--------------|
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| Pub/sub | Custom `Rooms` struct (~160 lines) | NATS subjects |
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| Member tracking | Manual `map[TU]Syncable` | NATS handles subscribers |
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| Publish timing | Ticker every 100ms + dirty flag | Instant delivery |
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| Durability | None (in-memory) | JetStream persists to disk |
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| Multi-instance | Not supported | Works across server instances |
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| External deps | None | **None** (NATS embedded in binary) |
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## Run the Example
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```bash
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go run ./internal/examples/nats-chatroom
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```
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That's it. No separate NATS server needed.
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Open multiple browser tabs at http://localhost:7331 to see messages broadcast across all clients.
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## How Embedded NATS Works
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```go
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// Start embedded NATS server (JetStream enabled by default)
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ns, err := embeddednats.New(ctx,
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embeddednats.WithDirectory("./data/nats"),
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)
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ns.WaitForServer()
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// Get client connection to embedded server
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nc, err := ns.Client()
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```
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Data is persisted to `./data/nats/` for JetStream durability.
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## Architecture
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```
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┌─────────────────────────────────────────────────────────┐
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│ Single Binary │
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│ │
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│ Browser A Embedded NATS Browser B │
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│ │ │ │ │
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│ │-- Via Action ---> │ │ │
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│ │ (Send msg) │ │ │
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│ │ │ │ │
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│ │ nc.Publish() │ │
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│ │ "chat.room.Go" │ │
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│ │ │ │ │
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│ │<-- Subscribe -----|---- Subscribe --->│ │
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│ │ callback │ callback │ │
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│ │ │ │ │
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│ │-- c.Sync() ------>│<--- c.Sync() -----| │
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│ │ (SSE) │ (SSE) │ │
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│ │
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└─────────────────────────────────────────────────────────┘
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```
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## JetStream Durability
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Messages persist to disk via JetStream:
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```go
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js.AddStream(&nats.StreamConfig{
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Name: "CHAT",
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Subjects: []string{"chat.>"},
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MaxMsgs: 1000, // Keep last 1000 messages
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MaxAge: 24 * time.Hour,
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})
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```
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Stop and restart the app - chat history survives.
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## Code Comparison
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**Original chatroom - 160+ lines of custom pub/sub:**
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- `Rooms` struct with named rooms
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- `Room` with member tracking, mutex, dirty flag
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- Ticker-based publish loop
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- Manual join/leave channels
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**This example - ~60 lines of NATS integration:**
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- `embeddednats.New()` starts the server
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- `nc.Subscribe(subject, handler)` for receiving
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- `nc.Publish(subject, data)` for sending
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- NATS handles delivery, no polling
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## Next Steps
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If this pattern proves useful, it could be promoted to a Via plugin:
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```go
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// Hypothetical future API
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v.Config(via.WithEmbeddedNATS("./data/nats"))
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// In page init
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c.Subscribe("events.user.*", func(data []byte) {
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c.Sync()
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})
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c.Publish("events.user.login", userData)
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```
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