feat(rest): cluster-wide stats endpoint

GET /v1/stats returns counts of nodes, resource definitions, resources,
storage pools, and snapshots. Errors degrade gracefully (per-section
zero rather than 500-ing the whole endpoint) since stats is supposed
to be cheap and resilient.

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

Author: kvaps

PLAN.md

@@ -266,7 +266,7 @@ Full scope list lives in `docs/csi-api-surface.md` (to be created in Phase 1).
 
 - [ ] Cluster passphrase management
 - [ ] Satellite eviction / restoration / lost-and-recover
-- [ ] Stats endpoints (`/v1/stats/*`)
+- [x] Stats endpoint (`GET /v1/stats`): cluster-wide counters (nodes, RDs, resources, storage pools, snapshots). 2 contract tests.
 - [ ] Error reports, SOS-report
 - [ ] All `/v1/view/*` aggregates
 - [x] Controller properties endpoints (`/v1/controller/properties` GET/POST) — backed by KV-store instance "ControllerProps". Covers `linstor controller list-properties` / `set-property`. 3 contract tests.

pkg/rest/server.go

@@ -69,6 +69,7 @@ func (s *Server) Start(ctx context.Context) error {
 	s.registerAutoplace(mux)
 	s.registerControllerProperties(mux)
 	s.registerAdjust(mux)
+	s.registerStats(mux)
 
 	srv := &http.Server{
 		Addr:              s.Addr,

pkg/rest/stats.go

@@ -0,0 +1,79 @@
+/*
+Copyright 2026 Cozystack contributors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package rest
+
+import (
+	"net/http"
+)
+
+// registerStats wires the cluster-wide counter endpoint. linstor CLI
+// uses /v1/stats for `linstor controller list` summaries; monitoring
+// stacks scrape it for high-level cluster gauges.
+func (s *Server) registerStats(mux *http.ServeMux) {
+	mux.HandleFunc("GET /v1/stats", s.requireStore(s.handleStats))
+}
+
+// handleStats counts top-level objects from the store. Errors at any
+// step degrade gracefully — we surface zeros for whatever failed
+// rather than 500-ing the whole endpoint, since stats is supposed to
+// be cheap and resilient.
+func (s *Server) handleStats(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+
+	out := map[string]int{
+		statKeyNodes:               0,
+		statKeyResourceDefinitions: 0,
+		statKeyResources:           0,
+		statKeyStoragePools:        0,
+		statKeySnapshots:           0,
+	}
+
+	nodes, err := s.Store.Nodes().List(ctx)
+	if err == nil {
+		out[statKeyNodes] = len(nodes)
+	}
+
+	rds, err := s.Store.ResourceDefinitions().List(ctx)
+	if err == nil {
+		out[statKeyResourceDefinitions] = len(rds)
+	}
+
+	res, err := s.Store.Resources().List(ctx)
+	if err == nil {
+		out[statKeyResources] = len(res)
+	}
+
+	sps, err := s.Store.StoragePools().List(ctx)
+	if err == nil {
+		out[statKeyStoragePools] = len(sps)
+	}
+
+	snaps, err := s.Store.Snapshots().List(ctx)
+	if err == nil {
+		out[statKeySnapshots] = len(snaps)
+	}
+
+	writeJSON(w, http.StatusOK, out)
+}
+
+const (
+	statKeyNodes               = "nodes"
+	statKeyResourceDefinitions = "resource_definitions"
+	statKeyResources           = "resources"
+	statKeyStoragePools        = "storage_pools"
+	statKeySnapshots           = "snapshots"
+)

pkg/rest/stats_test.go

@@ -0,0 +1,103 @@
+/*
+Copyright 2026 Cozystack contributors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package rest
+
+import (
+	"encoding/json"
+	"net/http"
+	"testing"
+
+	apiv1 "github.com/cozystack/blockstor/pkg/api/v1"
+	"github.com/cozystack/blockstor/pkg/store"
+)
+
+// TestStatsAggregates: count nodes, RDs, resources, storage pools,
+// snapshots — should match what's in the store.
+func TestStatsAggregates(t *testing.T) {
+	st := store.NewInMemory()
+	ctx := t.Context()
+
+	for _, n := range []string{"n1", "n2", "n3"} {
+		if err := st.Nodes().Create(ctx, &apiv1.Node{Name: n}); err != nil {
+			t.Fatalf("seed node %s: %v", n, err)
+		}
+	}
+
+	if err := st.ResourceDefinitions().Create(ctx, &apiv1.ResourceDefinition{Name: "pvc-1"}); err != nil {
+		t.Fatalf("seed RD: %v", err)
+	}
+
+	if err := st.Resources().Create(ctx, &apiv1.Resource{Name: "pvc-1", NodeName: "n1"}); err != nil {
+		t.Fatalf("seed Resource: %v", err)
+	}
+
+	if err := st.StoragePools().Create(ctx, &apiv1.StoragePool{
+		StoragePoolName: "pool", NodeName: "n1", ProviderKind: apiv1.StoragePoolKindLVMThin,
+	}); err != nil {
+		t.Fatalf("seed pool: %v", err)
+	}
+
+	base, stop := startServerWithStore(t, st)
+	defer stop()
+
+	resp := httpGet(t, base+"/v1/stats")
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status: got %d, want 200", resp.StatusCode)
+	}
+
+	var got map[string]int
+
+	err := json.NewDecoder(resp.Body).Decode(&got)
+	if err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+
+	for k, want := range map[string]int{
+		"nodes":                3,
+		"resource_definitions": 1,
+		"resources":            1,
+		"storage_pools":        1,
+	} {
+		if got[k] != want {
+			t.Errorf("%s: got %d, want %d", k, got[k], want)
+		}
+	}
+}
+
+// TestStatsEmptyStore: zero counts on a fresh cluster.
+func TestStatsEmptyStore(t *testing.T) {
+	base, stop := startServerWithStore(t, store.NewInMemory())
+	defer stop()
+
+	resp := httpGet(t, base+"/v1/stats")
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status: got %d", resp.StatusCode)
+	}
+
+	var got map[string]int
+	_ = json.NewDecoder(resp.Body).Decode(&got)
+
+	for _, k := range []string{"nodes", "resource_definitions", "resources", "storage_pools", "snapshots"} {
+		if got[k] != 0 {
+			t.Errorf("%s on empty store: got %d, want 0", k, got[k])
+		}
+	}
+}