Add database overview feature with metrics and UI enhancements

This commit introduces a detailed database overview endpoint and service, providing key metrics such as replication status, database sizes, and performance indicators. On the frontend, a new UI section displays these metrics along with improved forms and troubleshooting tips. Enhancements improve user experience by adding informative tooltips and formatting for byte and time values.

.env.example

@@ -17,6 +17,7 @@ JWT_ACCESS_TOKEN_MINUTES=15
 JWT_REFRESH_TOKEN_MINUTES=10080
 # Generate with: python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())"
 ENCRYPTION_KEY=REPLACE_WITH_FERNET_KEY
+# Dev: set to * to allow all origins (credentials disabled automatically)
 CORS_ORIGINS=http://localhost:5173,http://localhost:8080
 POLL_INTERVAL_SECONDS=30
 INIT_ADMIN_EMAIL=admin@example.com

backend/app/api/routes/targets.py

@@ -7,10 +7,12 @@ from app.core.db import get_db
 from app.core.deps import get_current_user, require_roles
 from app.models.models import Metric, QueryStat, Target, User
 from app.schemas.metric import MetricOut, QueryStatOut
+from app.schemas.overview import DatabaseOverviewOut
 from app.schemas.target import TargetCreate, TargetOut, TargetUpdate
 from app.services.audit import write_audit_log
 from app.services.collector import build_target_dsn
 from app.services.crypto import encrypt_secret
+from app.services.overview_service import get_target_overview
 
 router = APIRouter()
 
@@ -179,3 +181,12 @@ async def get_top_queries(target_id: int, user: User = Depends(get_current_user)
         )
         for r in rows
     ]
+
+
+@router.get("/{target_id}/overview", response_model=DatabaseOverviewOut)
+async def get_overview(target_id: int, user: User = Depends(get_current_user), db: AsyncSession = Depends(get_db)) -> DatabaseOverviewOut:
+    _ = user
+    target = await db.scalar(select(Target).where(Target.id == target_id))
+    if not target:
+        raise HTTPException(status_code=404, detail="Target not found")
+    return await get_target_overview(target)

backend/app/main.py

@@ -49,10 +49,11 @@ async def lifespan(_: FastAPI):
 
 
 app = FastAPI(title=settings.app_name, lifespan=lifespan)
+use_wildcard_cors = settings.cors_origins.strip() == "*"
 app.add_middleware(
     CORSMiddleware,
-    allow_origins=settings.cors_origins_list,
+    allow_origins=["*"] if use_wildcard_cors else settings.cors_origins_list,
-    allow_credentials=True,
+    allow_credentials=False if use_wildcard_cors else True,
     allow_methods=["*"],
     allow_headers=["*"],
 )

backend/app/schemas/overview.py

@@ -0,0 +1,79 @@
+from datetime import datetime
+from pydantic import BaseModel
+
+
+class DbSizeItem(BaseModel):
+    name: str
+    size_bytes: int
+
+
+class TableSizeItem(BaseModel):
+    schema: str
+    table: str
+    size_bytes: int
+
+
+class ReplicationClientItem(BaseModel):
+    application_name: str | None = None
+    client_addr: str | None = None
+    state: str | None = None
+    sync_state: str | None = None
+    write_lag_seconds: float | None = None
+    flush_lag_seconds: float | None = None
+    replay_lag_seconds: float | None = None
+    replay_lag_bytes: float | None = None
+
+
+class DiskSpaceInfo(BaseModel):
+    source: str
+    status: str
+    free_bytes: int | None = None
+    message: str | None = None
+
+
+class InstanceOverview(BaseModel):
+    server_version: str | None = None
+    role: str
+    postmaster_start_time: datetime | None = None
+    uptime_seconds: float | None = None
+    current_database: str | None = None
+    port: int | None = None
+
+
+class StorageOverview(BaseModel):
+    current_database_size_bytes: int | None = None
+    all_databases: list[DbSizeItem]
+    largest_tables: list[TableSizeItem]
+    wal_directory_size_bytes: int | None = None
+    disk_space: DiskSpaceInfo
+
+
+class ReplicationOverview(BaseModel):
+    mode: str
+    replay_lag_seconds: float | None = None
+    replication_slots_count: int | None = None
+    active_replication_clients: int | None = None
+    clients: list[ReplicationClientItem]
+
+
+class PerformanceOverview(BaseModel):
+    xact_commit: int | None = None
+    xact_rollback: int | None = None
+    deadlocks: int | None = None
+    temp_files: int | None = None
+    temp_bytes: int | None = None
+    blk_read_time: float | None = None
+    blk_write_time: float | None = None
+    checkpoints_timed: int | None = None
+    checkpoints_req: int | None = None
+    autovacuum_workers: int | None = None
+
+
+class DatabaseOverviewOut(BaseModel):
+    collected_at: datetime
+    cache_ttl_seconds: int
+    instance: InstanceOverview
+    storage: StorageOverview
+    replication: ReplicationOverview
+    performance: PerformanceOverview
+    partial_failures: list[str]

backend/app/services/infra_probe.py

@@ -0,0 +1,29 @@
+from dataclasses import dataclass
+
+
+@dataclass
+class DiskSpaceProbeResult:
+    source: str
+    status: str
+    free_bytes: int | None = None
+    message: str | None = None
+
+
+class DiskSpaceProvider:
+    async def get_free_bytes(self, target_host: str) -> DiskSpaceProbeResult:
+        raise NotImplementedError
+
+
+class NullDiskSpaceProvider(DiskSpaceProvider):
+    async def get_free_bytes(self, target_host: str) -> DiskSpaceProbeResult:
+        return DiskSpaceProbeResult(
+            source="none",
+            status="unavailable",
+            free_bytes=None,
+            message=f"No infra probe configured for host {target_host}. Add SSH/Agent provider later.",
+        )
+
+
+def get_disk_space_provider() -> DiskSpaceProvider:
+    # Extension point: replace by SSH/Agent backed implementation.
+    return NullDiskSpaceProvider()

backend/app/services/overview_collector.py

@@ -0,0 +1,218 @@
+from datetime import datetime, timezone
+import asyncpg
+from app.schemas.overview import (
+    DatabaseOverviewOut,
+    DbSizeItem,
+    DiskSpaceInfo,
+    InstanceOverview,
+    PerformanceOverview,
+    ReplicationClientItem,
+    ReplicationOverview,
+    StorageOverview,
+    TableSizeItem,
+)
+from app.services.infra_probe import DiskSpaceProvider
+
+
+def _interval_seconds(value) -> float | None:
+    if value is None:
+        return None
+    try:
+        return float(value.total_seconds())
+    except Exception:
+        return None
+
+
+async def _safe_fetchval(conn: asyncpg.Connection, query: str, errors: list[str], label: str):
+    try:
+        return await conn.fetchval(query)
+    except Exception as exc:
+        errors.append(f"{label}: {exc}")
+        return None
+
+
+async def _safe_fetchrow(conn: asyncpg.Connection, query: str, errors: list[str], label: str):
+    try:
+        return await conn.fetchrow(query)
+    except Exception as exc:
+        errors.append(f"{label}: {exc}")
+        return None
+
+
+async def _safe_fetch(conn: asyncpg.Connection, query: str, errors: list[str], label: str):
+    try:
+        return await conn.fetch(query)
+    except Exception as exc:
+        errors.append(f"{label}: {exc}")
+        return []
+
+
+async def collect_overview(
+    conn: asyncpg.Connection, disk_provider: DiskSpaceProvider, target_host: str, cache_ttl_seconds: int
+) -> DatabaseOverviewOut:
+    errors: list[str] = []
+
+    version = await _safe_fetchval(conn, "SHOW server_version", errors, "show_server_version")
+    in_recovery = await _safe_fetchval(conn, "SELECT pg_is_in_recovery()", errors, "pg_is_in_recovery")
+    postmaster_start = await _safe_fetchval(conn, "SELECT pg_postmaster_start_time()", errors, "postmaster_start")
+    current_db = await _safe_fetchval(conn, "SELECT current_database()", errors, "current_database")
+    port = await _safe_fetchval(conn, "SELECT inet_server_port()", errors, "inet_server_port")
+
+    uptime_seconds = None
+    if postmaster_start:
+        uptime_seconds = (datetime.now(timezone.utc) - postmaster_start).total_seconds()
+
+    db_size = await _safe_fetchval(
+        conn, "SELECT pg_database_size(current_database())", errors, "pg_database_size_current"
+    )
+    all_db_rows = await _safe_fetch(
+        conn,
+        """
+        SELECT datname, pg_database_size(datname) AS size_bytes
+        FROM pg_database
+        ORDER BY size_bytes DESC
+        """,
+        errors,
+        "pg_database_size_all",
+    )
+    largest_tables_rows = await _safe_fetch(
+        conn,
+        """
+        SELECT schemaname, relname, pg_total_relation_size(schemaname || '.' || relname) AS size_bytes
+        FROM pg_stat_user_tables
+        ORDER BY size_bytes DESC
+        LIMIT 5
+        """,
+        errors,
+        "largest_tables",
+    )
+    wal_dir_size = await _safe_fetchval(
+        conn,
+        """
+        SELECT COALESCE(sum(size), 0)
+        FROM pg_ls_waldir()
+        """,
+        errors,
+        "wal_directory_size",
+    )
+
+    stats_db = await _safe_fetchrow(
+        conn,
+        """
+        SELECT xact_commit, xact_rollback, deadlocks, temp_files, temp_bytes, blk_read_time, blk_write_time
+        FROM pg_stat_database
+        WHERE datname = current_database()
+        """,
+        errors,
+        "pg_stat_database_perf",
+    )
+    bgwriter = await _safe_fetchrow(
+        conn,
+        "SELECT checkpoints_timed, checkpoints_req FROM pg_stat_bgwriter",
+        errors,
+        "pg_stat_bgwriter",
+    )
+    autovac_workers = await _safe_fetchval(
+        conn,
+        """
+        SELECT count(*)
+        FROM pg_stat_activity
+        WHERE query ILIKE 'autovacuum:%'
+        """,
+        errors,
+        "autovacuum_activity",
+    )
+
+    clients: list[ReplicationClientItem] = []
+    replay_lag_seconds = None
+    slots_count = None
+    active_clients = None
+    role = "standby" if in_recovery else "primary"
+    if in_recovery:
+        replay_lag_seconds = await _safe_fetchval(
+            conn,
+            """
+            SELECT EXTRACT(EPOCH FROM (now() - pg_last_xact_replay_timestamp()))
+            """,
+            errors,
+            "standby_replay_lag",
+        )
+    else:
+        slots_count = await _safe_fetchval(conn, "SELECT count(*) FROM pg_replication_slots", errors, "replication_slots")
+        repl_rows = await _safe_fetch(
+            conn,
+            """
+            SELECT application_name, client_addr::text, state, sync_state,
+                   EXTRACT(EPOCH FROM write_lag) AS write_lag_seconds,
+                   EXTRACT(EPOCH FROM flush_lag) AS flush_lag_seconds,
+                   EXTRACT(EPOCH FROM replay_lag) AS replay_lag_seconds,
+                   pg_wal_lsn_diff(pg_current_wal_lsn(), replay_lsn) AS replay_lag_bytes
+            FROM pg_stat_replication
+            """,
+            errors,
+            "pg_stat_replication",
+        )
+        active_clients = len(repl_rows)
+        clients = [
+            ReplicationClientItem(
+                application_name=row.get("application_name"),
+                client_addr=row.get("client_addr"),
+                state=row.get("state"),
+                sync_state=row.get("sync_state"),
+                write_lag_seconds=row.get("write_lag_seconds"),
+                flush_lag_seconds=row.get("flush_lag_seconds"),
+                replay_lag_seconds=row.get("replay_lag_seconds"),
+                replay_lag_bytes=float(row.get("replay_lag_bytes")) if row.get("replay_lag_bytes") is not None else None,
+            )
+            for row in repl_rows
+        ]
+
+    disk = await disk_provider.get_free_bytes(target_host)
+
+    return DatabaseOverviewOut(
+        collected_at=datetime.now(timezone.utc),
+        cache_ttl_seconds=cache_ttl_seconds,
+        instance=InstanceOverview(
+            server_version=version,
+            role=role,
+            postmaster_start_time=postmaster_start,
+            uptime_seconds=uptime_seconds,
+            current_database=current_db,
+            port=int(port) if port is not None else None,
+        ),
+        storage=StorageOverview(
+            current_database_size_bytes=int(db_size) if db_size is not None else None,
+            all_databases=[DbSizeItem(name=r["datname"], size_bytes=int(r["size_bytes"])) for r in all_db_rows],
+            largest_tables=[
+                TableSizeItem(schema=r["schemaname"], table=r["relname"], size_bytes=int(r["size_bytes"]))
+                for r in largest_tables_rows
+            ],
+            wal_directory_size_bytes=int(wal_dir_size) if wal_dir_size is not None else None,
+            disk_space=DiskSpaceInfo(
+                source=disk.source,
+                status=disk.status,
+                free_bytes=disk.free_bytes,
+                message=disk.message,
+            ),
+        ),
+        replication=ReplicationOverview(
+            mode=role,
+            replay_lag_seconds=float(replay_lag_seconds) if replay_lag_seconds is not None else None,
+            replication_slots_count=int(slots_count) if slots_count is not None else None,
+            active_replication_clients=active_clients,
+            clients=clients,
+        ),
+        performance=PerformanceOverview(
+            xact_commit=stats_db["xact_commit"] if stats_db else None,
+            xact_rollback=stats_db["xact_rollback"] if stats_db else None,
+            deadlocks=stats_db["deadlocks"] if stats_db else None,
+            temp_files=stats_db["temp_files"] if stats_db else None,
+            temp_bytes=stats_db["temp_bytes"] if stats_db else None,
+            blk_read_time=stats_db["blk_read_time"] if stats_db else None,
+            blk_write_time=stats_db["blk_write_time"] if stats_db else None,
+            checkpoints_timed=bgwriter["checkpoints_timed"] if bgwriter else None,
+            checkpoints_req=bgwriter["checkpoints_req"] if bgwriter else None,
+            autovacuum_workers=int(autovac_workers) if autovac_workers is not None else None,
+        ),
+        partial_failures=errors,
+    )

backend/app/services/overview_service.py

@@ -0,0 +1,46 @@
+import asyncio
+import time
+import asyncpg
+from app.models.models import Target
+from app.schemas.overview import DatabaseOverviewOut
+from app.services.collector import build_target_dsn
+from app.services.infra_probe import get_disk_space_provider
+from app.services.overview_collector import collect_overview
+
+_CACHE_TTL_SECONDS = 20
+_cache: dict[int, tuple[float, DatabaseOverviewOut]] = {}
+_locks: dict[int, asyncio.Lock] = {}
+
+
+def _get_lock(target_id: int) -> asyncio.Lock:
+    if target_id not in _locks:
+        _locks[target_id] = asyncio.Lock()
+    return _locks[target_id]
+
+
+async def get_target_overview(target: Target) -> DatabaseOverviewOut:
+    now = time.time()
+    cached = _cache.get(target.id)
+    if cached and (now - cached[0]) < _CACHE_TTL_SECONDS:
+        return cached[1]
+
+    lock = _get_lock(target.id)
+    async with lock:
+        cached = _cache.get(target.id)
+        now = time.time()
+        if cached and (now - cached[0]) < _CACHE_TTL_SECONDS:
+            return cached[1]
+
+        conn = await asyncpg.connect(dsn=build_target_dsn(target))
+        try:
+            payload = await collect_overview(
+                conn=conn,
+                disk_provider=get_disk_space_provider(),
+                target_host=target.host,
+                cache_ttl_seconds=_CACHE_TTL_SECONDS,
+            )
+        finally:
+            await conn.close()
+
+        _cache[target.id] = (time.time(), payload)
+        return payload

frontend/src/pages/TargetDetailPage.jsx

@@ -17,6 +17,25 @@ function toQueryRange(range) {
   return { from: from.toISOString(), to: to.toISOString() };
 }
 
+function formatBytes(value) {
+  if (value === null || value === undefined) return "-";
+  const units = ["B", "KB", "MB", "GB", "TB"];
+  let n = Number(value);
+  let i = 0;
+  while (n >= 1024 && i < units.length - 1) {
+    n /= 1024;
+    i += 1;
+  }
+  return `${n.toFixed(i >= 2 ? 2 : 0)} ${units[i]}`;
+}
+
+function formatSeconds(value) {
+  if (value === null || value === undefined) return "-";
+  if (value < 60) return `${value.toFixed(1)}s`;
+  if (value < 3600) return `${(value / 60).toFixed(1)}m`;
+  return `${(value / 3600).toFixed(1)}h`;
+}
+
 async function loadMetric(targetId, metric, range, tokens, refresh) {
   const { from, to } = toQueryRange(range);
   return apiFetch(
@@ -34,6 +53,7 @@ export function TargetDetailPage() {
   const [series, setSeries] = useState({});
   const [locks, setLocks] = useState([]);
   const [activity, setActivity] = useState([]);
+  const [overview, setOverview] = useState(null);
   const [error, setError] = useState("");
   const [loading, setLoading] = useState(true);
 
@@ -42,17 +62,19 @@ export function TargetDetailPage() {
     (async () => {
       setLoading(true);
       try {
-        const [connections, xacts, cache, locksTable, activityTable] = await Promise.all([
+        const [connections, xacts, cache, locksTable, activityTable, overviewData] = await Promise.all([
           loadMetric(id, "connections_total", range, tokens, refresh),
           loadMetric(id, "xacts_total", range, tokens, refresh),
           loadMetric(id, "cache_hit_ratio", range, tokens, refresh),
           apiFetch(`/targets/${id}/locks`, {}, tokens, refresh),
           apiFetch(`/targets/${id}/activity`, {}, tokens, refresh),
+          apiFetch(`/targets/${id}/overview`, {}, tokens, refresh),
         ]);
         if (!active) return;
         setSeries({ connections, xacts, cache });
         setLocks(locksTable);
         setActivity(activityTable);
+        setOverview(overviewData);
         setError("");
       } catch (e) {
         if (active) setError(String(e.message || e));
@@ -79,9 +101,116 @@ export function TargetDetailPage() {
   if (loading) return <div className="card">Lade Target Detail...</div>;
   if (error) return <div className="card error">{error}</div>;
 
+  const role = overview?.instance?.role || "-";
+  const isPrimary = role === "primary";
+  const isStandby = role === "standby";
+
   return (
     <div>
       <h2>Target Detail #{id}</h2>
+      {overview && (
+        <div className="card">
+          <h3>Database Overview</h3>
+          <div className="grid three overview-kv">
+            <div><span>PostgreSQL Version</span><strong>{overview.instance.server_version || "-"}</strong></div>
+            <div>
+              <span>Role</span>
+              <strong className={isPrimary ? "pill primary" : isStandby ? "pill standby" : "pill"}>{role}</strong>
+            </div>
+            <div title="Zeit seit Start des Postgres-Prozesses">
+              <span>Uptime</span><strong>{formatSeconds(overview.instance.uptime_seconds)}</strong>
+            </div>
+            <div><span>Database</span><strong>{overview.instance.current_database || "-"}</strong></div>
+            <div><span>Port</span><strong>{overview.instance.port ?? "-"}</strong></div>
+            <div title="Groesse der aktuell verbundenen Datenbank">
+              <span>Current DB Size</span><strong>{formatBytes(overview.storage.current_database_size_bytes)}</strong>
+            </div>
+            <div title="Gesamtgroesse der WAL-Dateien (falls verfuegbar)">
+              <span>WAL Size</span><strong>{formatBytes(overview.storage.wal_directory_size_bytes)}</strong>
+            </div>
+            <div title="Optional ueber Agent/SSH ermittelbar">
+              <span>Free Disk</span><strong>{formatBytes(overview.storage.disk_space.free_bytes)}</strong>
+            </div>
+            <div title="Zeitliche Replikationsverzoegerung auf Standby">
+              <span>Replay Lag</span>
+              <strong className={overview.replication.replay_lag_seconds > 5 ? "lag-bad" : ""}>
+                {formatSeconds(overview.replication.replay_lag_seconds)}
+              </strong>
+            </div>
+            <div><span>Replication Slots</span><strong>{overview.replication.replication_slots_count ?? "-"}</strong></div>
+            <div><span>Repl Clients</span><strong>{overview.replication.active_replication_clients ?? "-"}</strong></div>
+            <div><span>Autovacuum Workers</span><strong>{overview.performance.autovacuum_workers ?? "-"}</strong></div>
+          </div>
+
+          <div className="grid two">
+            <div>
+              <h4>Size all databases</h4>
+              <table>
+                <thead><tr><th>Database</th><th>Size</th></tr></thead>
+                <tbody>
+                  {(overview.storage.all_databases || []).map((d) => (
+                    <tr key={d.name}><td>{d.name}</td><td>{formatBytes(d.size_bytes)}</td></tr>
+                  ))}
+                </tbody>
+              </table>
+            </div>
+            <div>
+              <h4>Largest Tables (Top 5)</h4>
+              <table>
+                <thead><tr><th>Table</th><th>Size</th></tr></thead>
+                <tbody>
+                  {(overview.storage.largest_tables || []).map((t, i) => (
+                    <tr key={`${t.schema}.${t.table}.${i}`}><td>{t.schema}.{t.table}</td><td>{formatBytes(t.size_bytes)}</td></tr>
+                  ))}
+                </tbody>
+              </table>
+            </div>
+          </div>
+
+          <div className="grid two">
+            <div>
+              <h4>Replication Clients</h4>
+              <table>
+                <thead><tr><th>Client</th><th>State</th><th>Lag</th></tr></thead>
+                <tbody>
+                  {(overview.replication.clients || []).map((c, i) => (
+                    <tr key={`${c.client_addr || "n/a"}-${i}`}>
+                      <td>{c.client_addr || c.application_name || "-"}</td>
+                      <td>{c.state || "-"}</td>
+                      <td className={(c.replay_lag_seconds || 0) > 5 ? "lag-bad" : ""}>
+                        {c.replay_lag_seconds != null ? formatSeconds(c.replay_lag_seconds) : formatBytes(c.replay_lag_bytes)}
+                      </td>
+                    </tr>
+                  ))}
+                </tbody>
+              </table>
+            </div>
+            <div>
+              <h4>Performance Core Metrics</h4>
+              <div className="overview-metrics">
+                <div><span>xact_commit</span><strong>{overview.performance.xact_commit ?? "-"}</strong></div>
+                <div><span>xact_rollback</span><strong>{overview.performance.xact_rollback ?? "-"}</strong></div>
+                <div><span>deadlocks</span><strong>{overview.performance.deadlocks ?? "-"}</strong></div>
+                <div><span>temp_files</span><strong>{overview.performance.temp_files ?? "-"}</strong></div>
+                <div><span>temp_bytes</span><strong>{formatBytes(overview.performance.temp_bytes)}</strong></div>
+                <div><span>blk_read_time</span><strong>{overview.performance.blk_read_time ?? "-"} ms</strong></div>
+                <div><span>blk_write_time</span><strong>{overview.performance.blk_write_time ?? "-"} ms</strong></div>
+                <div><span>checkpoints_timed</span><strong>{overview.performance.checkpoints_timed ?? "-"}</strong></div>
+                <div><span>checkpoints_req</span><strong>{overview.performance.checkpoints_req ?? "-"}</strong></div>
+              </div>
+            </div>
+          </div>
+
+          {overview.partial_failures?.length > 0 && (
+            <div className="partial-warning">
+              <strong>Partial data warnings:</strong>
+              <ul>
+                {overview.partial_failures.map((w, i) => <li key={i}>{w}</li>)}
+              </ul>
+            </div>
+          )}
+        </div>
+      )}
       <div className="range-picker">
         {Object.keys(ranges).map((r) => (
           <button key={r} onClick={() => setRange(r)} className={r === range ? "active" : ""}>

frontend/src/pages/TargetsPage.jsx

@@ -66,20 +66,67 @@ export function TargetsPage() {
       {error && <div className="card error">{error}</div>}
       {canManage && (
         <form className="card grid two" onSubmit={createTarget}>
-          <input placeholder="Name" value={form.name} onChange={(e) => setForm({ ...form, name: e.target.value })} required />
+          <div className="field">
-          <input placeholder="Host" value={form.host} onChange={(e) => setForm({ ...form, host: e.target.value })} required />
+            <label>Name</label>
-          <input placeholder="Port" value={form.port} onChange={(e) => setForm({ ...form, port: Number(e.target.value) })} type="number" />
+            <input placeholder="z.B. Prod-DB" value={form.name} onChange={(e) => setForm({ ...form, name: e.target.value })} required />
-          <input placeholder="DB Name" value={form.dbname} onChange={(e) => setForm({ ...form, dbname: e.target.value })} required />
+            <small>Eindeutiger Anzeigename im Dashboard.</small>
-          <input placeholder="Username" value={form.username} onChange={(e) => setForm({ ...form, username: e.target.value })} required />
+          </div>
-          <input placeholder="Passwort" type="password" value={form.password} onChange={(e) => setForm({ ...form, password: e.target.value })} required />
+          <div className="field">
-          <select value={form.sslmode} onChange={(e) => setForm({ ...form, sslmode: e.target.value })}>
+            <label>Host</label>
-            <option value="disable">disable</option>
+            <input placeholder="z.B. 172.16.0.106 oder db.internal" value={form.host} onChange={(e) => setForm({ ...form, host: e.target.value })} required />
-            <option value="prefer">prefer</option>
+            <small>Wichtig: Muss vom Backend-Container aus erreichbar sein.</small>
-            <option value="require">require</option>
+          </div>
-          </select>
+          <div className="field">
-          <button>Target anlegen</button>
+            <label>Port</label>
+            <input placeholder="5432" value={form.port} onChange={(e) => setForm({ ...form, port: Number(e.target.value) })} type="number" required />
+            <small>Standard PostgreSQL Port ist 5432 (oder gemappter Host-Port).</small>
+          </div>
+          <div className="field">
+            <label>DB Name</label>
+            <input placeholder="z.B. postgres oder appdb" value={form.dbname} onChange={(e) => setForm({ ...form, dbname: e.target.value })} required />
+            <small>Name der Datenbank, die überwacht werden soll.</small>
+          </div>
+          <div className="field">
+            <label>Username</label>
+            <input placeholder="z.B. postgres" value={form.username} onChange={(e) => setForm({ ...form, username: e.target.value })} required />
+            <small>DB User mit Leserechten auf Stats-Views.</small>
+          </div>
+          <div className="field">
+            <label>Password</label>
+            <input placeholder="Passwort" type="password" value={form.password} onChange={(e) => setForm({ ...form, password: e.target.value })} required />
+            <small>Wird verschlüsselt in der Core-DB gespeichert.</small>
+          </div>
+          <div className="field">
+            <label>SSL Mode</label>
+            <select value={form.sslmode} onChange={(e) => setForm({ ...form, sslmode: e.target.value })}>
+              <option value="disable">disable</option>
+              <option value="prefer">prefer</option>
+              <option value="require">require</option>
+            </select>
+            <small>
+              Bei Fehler "rejected SSL upgrade" auf <code>disable</code> stellen.
+            </small>
+          </div>
+          <div className="field">
+            <label>&nbsp;</label>
+            <button>Target anlegen</button>
+          </div>
         </form>
       )}
+      {canManage && (
+        <div className="card tips">
+          <strong>Troubleshooting</strong>
+          <p>
+            <code>Connection refused</code>: Host/Port falsch oder DB nicht erreichbar.
+          </p>
+          <p>
+            <code>rejected SSL upgrade</code>: SSL Mode auf <code>disable</code> setzen.
+          </p>
+          <p>
+            <code>localhost</code> im Target zeigt aus Backend-Container-Sicht auf den Container selbst.
+          </p>
+        </div>
+      )}
       <div className="card">
         {loading ? (
           <p>Lade Targets...</p>

frontend/src/styles.css

@@ -96,6 +96,26 @@ button {
   padding: 10px;
 }
 
+.field {
+  display: grid;
+  gap: 6px;
+}
+
+.field label {
+  font-size: 13px;
+  color: #b9c6dc;
+}
+
+.field small {
+  font-size: 12px;
+  color: #8fa0bf;
+}
+
+.tips p {
+  margin: 8px 0;
+  color: #bfd0ea;
+}
+
 button {
   cursor: pointer;
 }
@@ -147,6 +167,53 @@ td {
   text-overflow: ellipsis;
 }
 
+.overview-kv span,
+.overview-metrics span {
+  display: block;
+  font-size: 12px;
+  color: #97a7c8;
+}
+
+.overview-kv strong,
+.overview-metrics strong {
+  font-size: 15px;
+}
+
+.overview-metrics {
+  display: grid;
+  grid-template-columns: repeat(2, minmax(0, 1fr));
+  gap: 10px;
+}
+
+.pill {
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+}
+
+.pill.primary {
+  color: #4ade80;
+}
+
+.pill.standby {
+  color: #f59e0b;
+}
+
+.lag-bad {
+  color: #ef4444;
+}
+
+.partial-warning {
+  margin-top: 12px;
+  border: 1px solid #7f1d1d;
+  border-radius: 10px;
+  padding: 10px;
+  color: #fecaca;
+}
+
+.partial-warning ul {
+  margin: 8px 0 0 18px;
+}
+
 @media (max-width: 980px) {
   .shell {
     grid-template-columns: 1fr;