Implement radar-telemt-dcs aggregation endpoint and UI integration

- Added new API route `/api/agg/radar-telemt-dcs` to aggregate DC status data from multiple upstreams, including metrics like coverage percentage and RTT.
- Implemented handler logic in `handlers.go` and corresponding tests in `handlers_test.go` to ensure correct data retrieval and response formatting.
- Updated the frontend to fetch and display radar DC data, enhancing the user interface with a new section for Telemt ME snapshots.
- Enhanced documentation in `AGGREGATE.md` and `README.md` to reflect the new functionality and usage details.

internal/aggregate/handlers.go

@@ -113,6 +113,8 @@ func (h *Handler) dispatch(w http.ResponseWriter, r *http.Request, sub string) {
 		h.handleUsers(w, r)
 	case sub == "fleet-status":
 		h.handleFleetStatus(w, r)
+	case sub == "radar-telemt-dcs":
+		h.handleRadarTelemtDcs(w, r)
 	case sub == "incidents":
 		h.handleIncidents(w, r)
 	case strings.HasPrefix(sub, "user/"):
@@ -275,6 +277,25 @@ func (h *Handler) handleUsers(w http.ResponseWriter, r *http.Request) {
 	writeAggOK(w, partial, data)
 }
 
+func (h *Handler) handleRadarTelemtDcs(w http.ResponseWriter, r *http.Request) {
+	aliases, err := h.resolveAliases(r)
+	if err != nil {
+		writeBadRequest(w, err)
+		return
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 60*time.Second)
+	defer cancel()
+	data := FetchRadarTelemtDcs(ctx, h.Client, h.Parsed, aliases)
+	partial := false
+	for _, s := range data.Servers {
+		if !s.OK {
+			partial = true
+			break
+		}
+	}
+	writeAggOK(w, partial, data)
+}
+
 func (h *Handler) handleFleetStatus(w http.ResponseWriter, r *http.Request) {
 	aliases, err := h.resolveAliases(r)
 	if err != nil {

internal/aggregate/handlers_test.go

@@ -113,6 +113,65 @@ func TestHandlerFleetStatus(t *testing.T) {
 	}
 }
 
+func TestHandlerRadarTelemtDcs(t *testing.T) {
+	up := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/v1/stats/dcs" {
+			http.NotFound(w, r)
+			return
+		}
+		_ = json.NewEncoder(w).Encode(map[string]any{
+			"ok": true,
+			"data": map[string]any{
+				"middle_proxy_enabled":     true,
+				"generated_at_epoch_secs":  1,
+				"dcs": []map[string]any{{
+					"dc": 1, "rtt_ms": 42.5, "coverage_pct": 100.0,
+					"alive_writers": 3, "required_writers": 3, "load": 0,
+				}},
+			},
+			"revision": "rd",
+		})
+	}))
+	defer up.Close()
+
+	cfg := &config.Config{
+		Servers: []config.Server{
+			{Alias: "test", BaseURL: up.URL, PathPrefix: "/v1"},
+		},
+	}
+	if err := cfg.Validate(); err != nil {
+		t.Fatal(err)
+	}
+	parsed, err := cfg.Parse()
+	if err != nil {
+		t.Fatal(err)
+	}
+	h := NewHandler(parsed, up.Client(), nil, 0)
+	req := httptest.NewRequest(http.MethodGet, "/api/agg/radar-telemt-dcs?aliases=test", nil)
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status %d body %s", rec.Code, rec.Body.String())
+	}
+	var env struct {
+		OK   bool             `json:"ok"`
+		Data RadarTelemtDcsData `json:"data"`
+	}
+	if err := json.Unmarshal(rec.Body.Bytes(), &env); err != nil {
+		t.Fatal(err)
+	}
+	if !env.OK || len(env.Data.Servers) != 1 {
+		t.Fatalf("envelope: %+v", env)
+	}
+	row := env.Data.Servers[0]
+	if row.Alias != "test" || !row.OK || row.Data == nil || !row.Data.MiddleProxyEnabled {
+		t.Fatalf("row: %+v", row)
+	}
+	if len(row.Data.Dcs) != 1 || row.Data.Dcs[0].DC != 1 {
+		t.Fatalf("dcs: %+v", row.Data.Dcs)
+	}
+}
+
 func TestHandlerUserOne(t *testing.T) {
 	up := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.URL.Path != "/v1/stats/users" {

internal/aggregate/radar_telemt.go

@@ -0,0 +1,44 @@
+package aggregate
+
+import (
+	"context"
+	"net/http"
+	"sort"
+	"sync"
+
+	"github.com/telemt/telemt-api/internal/config"
+)
+
+const statsDcsPath = "stats/dcs"
+
+// FetchRadarTelemtDcs calls GET /v1/stats/dcs on each Telemt in parallel.
+func FetchRadarTelemtDcs(ctx context.Context, client *http.Client, parsed *config.Parsed, aliases []string) RadarTelemtDcsData {
+	if len(aliases) == 0 {
+		return RadarTelemtDcsData{}
+	}
+	rows := make([]RadarTelemtDcsServer, len(aliases))
+	var wg sync.WaitGroup
+	for i, alias := range aliases {
+		i, alias := i, alias
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			data, meta := FetchTelemtGET[DcStatusPayload](ctx, client, parsed, alias, statsDcsPath)
+			row := RadarTelemtDcsServer{
+				Alias:      alias,
+				OK:         meta.OK,
+				HTTPStatus: meta.HTTPStatus,
+				LatencyMs:  meta.LatencyMs,
+				Error:      meta.Error,
+				Revision:   meta.Revision,
+			}
+			if meta.OK {
+				row.Data = &data
+			}
+			rows[i] = row
+		}()
+	}
+	wg.Wait()
+	sort.Slice(rows, func(i, j int) bool { return rows[i].Alias < rows[j].Alias })
+	return RadarTelemtDcsData{Servers: rows}
+}

internal/aggregate/types.go

@@ -206,3 +206,37 @@ type TopUserByUniqueIPs struct {
 	Username  string `json:"username"`
 	UniqueIPs uint64 `json:"unique_ips"`
 }
+
+// DcStatusRow mirrors Telemt GET /v1/stats/dcs data.dcs[] (subset for radar UI).
+type DcStatusRow struct {
+	DC              int      `json:"dc"`
+	RttMs           *float64 `json:"rtt_ms"`
+	CoveragePct     float64  `json:"coverage_pct"`
+	AliveWriters    int      `json:"alive_writers"`
+	RequiredWriters int      `json:"required_writers"`
+	Load            int      `json:"load"`
+}
+
+// DcStatusPayload mirrors Telemt GET /v1/stats/dcs data object.
+type DcStatusPayload struct {
+	MiddleProxyEnabled   bool          `json:"middle_proxy_enabled"`
+	Reason               *string       `json:"reason"`
+	GeneratedAtEpochSecs uint64        `json:"generated_at_epoch_secs"`
+	Dcs                  []DcStatusRow `json:"dcs"`
+}
+
+// RadarTelemtDcsServer is one upstream stats/dcs outcome for /api/agg/radar-telemt-dcs.
+type RadarTelemtDcsServer struct {
+	Alias      string           `json:"alias"`
+	OK         bool             `json:"ok"`
+	HTTPStatus int              `json:"http_status,omitempty"`
+	LatencyMs  int64            `json:"latency_ms,omitempty"`
+	Error      string           `json:"error,omitempty"`
+	Revision   string           `json:"revision,omitempty"`
+	Data       *DcStatusPayload `json:"data,omitempty"`
+}
+
+// RadarTelemtDcsData is aggregate payload for /api/agg/radar-telemt-dcs.
+type RadarTelemtDcsData struct {
+	Servers []RadarTelemtDcsServer `json:"servers"`
+}