Create DISCOVERY.md

Author: lmangani

docs/DISCOVERY.md

@@ -0,0 +1,71 @@
+## Discovery API
+
+- [x] POST `/subscribe/{secretHash}` - Register a peer
+- [x] GET `/discovery/{secretHash}` - Get list of active peers
+- [x] DELETE `/unsubscribe/{secretHash}/{peerId}` - Remove peer
+
+### Start Server
+```sql
+D SELECT httpserve_enable_discovery('true');
+D SELECT httpserve_start('0.0.0.0',9999, '');
+┌──────────────────────────────────────┐
+│ httpserve_start('0.0.0.0', 9999, '') │
+│               varchar                │
+├──────────────────────────────────────┤
+│ HTTP server started on 0.0.0.0:9999  │
+└──────────────────────────────────────┘
+```
+
+### Register a Peer under a secret hash
+#### CURL
+```bash
+curl -X POST "https://localhost:9999/subscribe/secretHash" \
+  -H "Content-Type: application/json" \
+  -d '{ "name": "service1", "endpoint": "http://192.168.1.100:8080", "ttl": 300 }
+```
+#### SQL
+```sql
+INSTALL http_client FROM community; LOAD http_client; LOAD json;
+WITH __input AS (
+    SELECT
+      http_post(
+          'http://localhost:9999/subscribe/secretHash',
+          headers => MAP {
+          },
+          params => MAP {
+            'name': 'quackpipe1',
+            'endpoint': 'https://1.1.1.1',
+          }
+      ) AS res
+  ) SELECT res->>'reason' as res, res->>'status' as status FROM __input;
+```
+
+### Check `peers` table
+```sql
+D SELECT name, endpoint, source_address as sourceAddress, peer_id as peerId, metadata, ttl, strftime(registered_at, '%Y-%m-%d %H:%M:%S') as registered_at FROM peers WHERE hash = 'secretHash';
+┌──────────┬───────────────────────────┬───────────────┬──────────────────────────────────┬──────────┬───────┬─────────────────────┐
+│   name   │         endpoint          │ sourceAddress │              peerId              │ metadata │  ttl  │    registered_at    │
+│ varchar  │          varchar          │    varchar    │             varchar              │ varchar  │ int64 │       varchar       │
+├──────────┼───────────────────────────┼───────────────┼──────────────────────────────────┼──────────┼───────┼─────────────────────┤
+│ service1 │ http://192.168.1.100:8080 │ xxx.xx.xx.xxx │ 0872c98634ce7e608e19aa1a1e6cf784 │ {}       │   300 │ 2024-11-14 19:44:23 │
+└──────────┴───────────────────────────┴───────────────┴──────────────────────────────────┴──────────┴───────┴─────────────────────┘
+```
+
+### Discover Peers
+#### CURL
+```bash
+curl "http://localhost:9999/discovery/secretHash"
+```
+#### SQL 
+```sql
+D SELECT * FROM read_ndjson_auto('http://localhost:9999/discovery/secretHash');
+┌──────────┬──────────────────────┬────────────────┬──────────────────────────────┬──────────┬─────────┬─────────────────────┐
+│   name   │       endpoint       │ source_address │           peer_id            │ metadata │   ttl   │    registered_at    │
+│ varchar  │       varchar        │    varchar     │             uuid             │ varchar  │ varchar │      timestamp      │
+├──────────┼──────────────────────┼────────────────┼──────────────────────────────┼──────────┼─────────┼─────────────────────┤
+│ service1 │ http://192.168.1.1…  │ 127.0.0.1      │ 0872c986-34ce-7e60-8e19-aa…  │          │ 3600    │ 2024-11-15 14:13:50 │
+└──────────┴──────────────────────┴────────────────┴──────────────────────────────┴──────────┴─────────┴─────────────────────┘
+D
+```
+
+⚠️ minor issue with peer_id being a UUID and clients hating it