feat(dashboard): Org-aware cache for schema migration (#115025)

* fix: use dsIndexProvider cache on migrations

* chore: use same comment as before

* feat: org-aware TTL cache for schemaversion migration and warmup for single tenant

* chore: use LRU cache

* chore: change DefaultCacheTTL to 1 minute

* chore: address copilot reviews

* chore: use expirable cache

* chore: remove unused import

apps/dashboard/pkg/migration/schemaversion/cache.go

@@ -0,0 +1,104 @@
+package schemaversion
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"github.com/grafana/authlib/types"
+	"github.com/grafana/grafana/pkg/infra/log"
+	"github.com/hashicorp/golang-lru/v2/expirable"
+	k8srequest "k8s.io/apiserver/pkg/endpoints/request"
+
+	"github.com/grafana/grafana/pkg/services/apiserver/endpoints/request"
+)
+
+const defaultCacheSize = 1000
+
+// CacheProvider is a generic cache interface for schema version providers.
+type CacheProvider[T any] interface {
+	// Get returns the cached value if it's still valid, otherwise calls fetch and caches the result.
+	Get(ctx context.Context) T
+}
+
+// PreloadableCache is an interface for providers that support preloading the cache.
+type PreloadableCache interface {
+	// Preload loads data into the cache for the given namespaces.
+	Preload(ctx context.Context, nsInfos []types.NamespaceInfo)
+}
+
+// cachedProvider is a thread-safe TTL cache that wraps any fetch function.
+type cachedProvider[T any] struct {
+	fetch    func(context.Context) T
+	cache    *expirable.LRU[string, T] // LRU cache: namespace to cache entry
+	inFlight sync.Map                  // map[string]*sync.Mutex - per-namespace fetch locks
+	logger   log.Logger
+}
+
+// newCachedProvider creates a new cachedProvider.
+// The fetch function should be able to handle context with different namespaces.
+// A non-positive size turns LRU mechanism off (cache of unlimited size).
+// A non-positive cacheTTL disables TTL expiration.
+func newCachedProvider[T any](fetch func(context.Context) T, size int, cacheTTL time.Duration, logger log.Logger) *cachedProvider[T] {
+	cacheProvider := &cachedProvider[T]{
+		fetch:  fetch,
+		logger: logger,
+	}
+	cacheProvider.cache = expirable.NewLRU(size, func(key string, value T) {
+		cacheProvider.inFlight.Delete(key)
+	}, cacheTTL)
+	return cacheProvider
+}
+
+// Get returns the cached value if it's still valid, otherwise calls fetch and caches the result.
+func (p *cachedProvider[T]) Get(ctx context.Context) T {
+	// Get namespace info from ctx
+	nsInfo, err := request.NamespaceInfoFrom(ctx, true)
+	if err != nil {
+		// No namespace, fall back to direct fetch call without caching
+		p.logger.Warn("Unable to get namespace info from context, skipping cache", "error", err)
+		return p.fetch(ctx)
+	}
+
+	namespace := nsInfo.Value
+	// Fast path: check if cache is still valid
+	if entry, ok := p.cache.Get(namespace); ok {
+		return entry
+	}
+
+	// Get or create a per-namespace lock for this fetch operation
+	// This ensures only one fetch happens per namespace at a time
+	lockInterface, _ := p.inFlight.LoadOrStore(namespace, &sync.Mutex{})
+	nsMutex := lockInterface.(*sync.Mutex)
+
+	// Lock this specific namespace - other namespaces can still proceed
+	nsMutex.Lock()
+	defer nsMutex.Unlock()
+
+	// Double-check: another goroutine might have already fetched while we waited
+	if entry, ok := p.cache.Get(namespace); ok {
+		return entry
+	}
+
+	// Fetch outside the main lock - only this namespace is blocked
+	p.logger.Debug("cache miss or expired, fetching new value", "namespace", namespace)
+	value := p.fetch(ctx)
+
+	// Update the cache for this namespace
+	p.cache.Add(namespace, value)
+
+	return value
+}
+
+// Preload loads data into the cache for the given namespaces.
+func (p *cachedProvider[T]) Preload(ctx context.Context, nsInfos []types.NamespaceInfo) {
+	// Build the cache using a context with the namespace
+	p.logger.Info("preloading cache", "nsInfos", len(nsInfos))
+	startedAt := time.Now()
+	defer func() {
+		p.logger.Info("finished preloading cache", "nsInfos", len(nsInfos), "elapsed", time.Since(startedAt))
+	}()
+	for _, nsInfo := range nsInfos {
+		p.cache.Add(nsInfo.Value, p.fetch(k8srequest.WithNamespace(ctx, nsInfo.Value)))
+	}
+}