Add docker-compose, README, fix SSE dispatch

Use Undertow dispatch for SSE handler to avoid Ring adapter conflict.
Add docker-compose.yml (port 4101 to coexist with local dev on 4100).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -8,6 +8,16 @@ Bitcoin data backend — Clojure Kit application. Fetches BTC prices from Binanc
 - `make repl` — Start nREPL
 - `make test` — Run tests
 - `make uberjar` — Build production JAR
+- `docker compose up -d` — Start btcdata container
+
+## Docker
+
+Docker runs alongside local dev on different ports and databases:
+
+| | Local dev      | Docker         |
+|--|----------------|----------------|
+| **Port** | localhost:4100 | localhost:4101 |
+| **Database** | btcprice | btcprod |
 
 ## REPL Commands
 

README.md

@@ -0,0 +1,40 @@
+# btcdata
+
+Bitcoin data backend service. Fetches BTC prices from Binance (WebSocket) and Kraken (HTTP polling), stores them in PostgreSQL, and exposes a JSON API with Server-Sent Events for live price streaming.
+
+## API
+
+| Endpoint | Description |
+|---|---|
+| `GET /api/price/stream` | SSE stream — emits `price-update` events with JSON `{price, prev_price, recorded_at}` |
+| `GET /api/price/latest` | Latest price as JSON |
+| `GET /api/health` | Health check |
+
+## Quick Start
+
+```bash
+# Local dev (requires PostgreSQL)
+cp .env.example .env   # edit JDBC_URL
+make run               # starts on port 4100
+
+# Docker
+docker compose up -d   # starts on port 4101
+```
+
+## Environment Variables
+
+| Variable | Default | Description |
+|---|---|---|
+| `BTCDATA_PORT` | `4100` | HTTP server port |
+| `JDBC_URL` | — | PostgreSQL connection string |
+| `CORS_ORIGIN` | `*` | Allowed origin for CORS headers |
+
+## Data Sources
+
+- **Binance** — WebSocket trade stream (`btcusdt@trade`), throttled to 5s writes
+- **Kraken hourly** — OHLC candles polled at HH:01:00 UTC
+- **Kraken daily** — OHLC candles polled at 00:01:00 UTC
+
+## Tech Stack
+
+Clojure · Kit · Undertow · Reitit · PostgreSQL · conman · Migratus

docker-compose.yml

@@ -0,0 +1,12 @@
+services:
+  btcdata:
+    build: .
+    restart: unless-stopped
+    ports:
+      - "4101:4100"
+    environment:
+      BTCDATA_PORT: "4100"
+      JDBC_URL: "jdbc:postgresql://postgres:5432/btcprod?user=postgres&password=ratata,123"
+      CORS_ORIGIN: "http://localhost:4041"
+    extra_hosts:
+      - "postgres:host-gateway"

src/clj/pmagnus/btcdata/web/routes/api.clj

@@ -28,11 +28,8 @@
     :prev_price  (when prev-price (str prev-price))
     :recorded_at (str recorded-at)}))
 
-(defn- price-stream-handler [{:keys [binance]} req]
+(defn- run-sse-loop! [^HttpServerExchange exchange price-atom cors-origin]
-  (let [^HttpServerExchange exchange (:server-exchange req)
+  (let [headers (.getResponseHeaders exchange)]
-        price-atom (:latest-price binance)
-        headers    (.getResponseHeaders exchange)
-        cors-origin (or (System/getenv "CORS_ORIGIN") "*")]
     (.setStatusCode exchange 200)
     (.put headers (HttpString. "Content-Type") "text/event-stream")
     (.put headers (HttpString. "Cache-Control") "no-cache")
@@ -59,7 +56,21 @@
         (catch Exception _)
         (finally
           (remove-watch price-atom wkey)
-          (try (.close writer) (catch Exception _)))))
+          (try (.close writer) (catch Exception _))
+          (when-not (.isComplete exchange)
+            (.endExchange exchange)))))))
+
+(defn- price-stream-handler [{:keys [binance]} req]
+  (let [^HttpServerExchange exchange (:server-exchange req)
+        price-atom  (:latest-price binance)
+        cors-origin (or (System/getenv "CORS_ORIGIN") "*")]
+    ;; Dispatch to a worker thread so the Ring adapter never processes
+    ;; the return value — Undertow handles the exchange lifecycle directly.
+    (.dispatch exchange
+      (reify io.undertow.server.HttpHandler
+        (handleRequest [_ ex]
+          (run-sse-loop! ex price-atom cors-origin))))
+    ;; Return nil; exchange is dispatched so adapter won't touch it.
     nil))
 
 (defn- latest-price-handler [{:keys [binance]} _req]