feat: introduce ttl cache for bleve indices (#106842)

pkg/setting/setting.go

@@ -561,6 +561,7 @@ type Cfg struct {
 	IndexFileThreshold                         int
 	IndexMinCount                              int
 	IndexRebuildInterval                       time.Duration
+	IndexCacheTTL                              time.Duration
 	EnableSharding                             bool
 	MemberlistBindAddr                         string
 	MemberlistAdvertiseAddr                    string

pkg/setting/setting_unified_storage.go

@@ -66,6 +66,7 @@ func (cfg *Cfg) setUnifiedStorageConfig() {
 	cfg.IndexMinCount = section.Key("index_min_count").MustInt(1)
 	// default to 24 hours because usage insights summarizes the data every 24 hours
 	cfg.IndexRebuildInterval = section.Key("index_rebuild_interval").MustDuration(24 * time.Hour)
+	cfg.IndexCacheTTL = section.Key("index_cache_ttl").MustDuration(10 * time.Minute)
 	cfg.SprinklesApiServer = section.Key("sprinkles_api_server").String()
 	cfg.SprinklesApiServerPageLimit = section.Key("sprinkles_api_server_page_limit").MustInt(100)
 	cfg.CACertPath = section.Key("ca_cert_path").String()