chore(perf): Pre-allocate where possible (enable prealloc linter) (#88952)

* chore(perf): Pre-allocate where possible (enable prealloc linter)

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>

* fix TestAlertManagers_buildRedactedAMs

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>

* prealloc a slice that appeared after rebase

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>

---------

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>

.golangci.toml

@@ -129,14 +129,20 @@ max-func-lines = 60
 
 [linters]
 disable-all = true
+# try to keep this list sorted, please
 enable = [
+  "asciicheck",
   "bodyclose",
   "depguard",
   "dogsled",
   "errcheck",
+  "errorlint",
+  "exhaustive",
+  "exportloopref",
   # "gochecknoinits",
   # "goconst",
   # "gocritic", # Temporarily disabled on 2022-09-09, running into weird bug "ruleguard: execution error: used Run() with an empty rule set; forgot to call Load() first?"
+  "gocyclo",
   "goimports",
   "goprintffuncname",
   "gosec",
@@ -145,19 +151,14 @@ enable = [
   "ineffassign",
   "misspell",
   "nakedret",
-  "exportloopref",
+  "prealloc",
+  "revive",
   "staticcheck",
   "stylecheck",
   "typecheck",
   "unconvert",
   "unused",
   "whitespace",
-  "gocyclo",
-  "exhaustive",
-  "typecheck",
-  "asciicheck",
-  "errorlint",
-  "revive",
 ]
 
 # Disabled linters (might want them later)

pkg/build/cmd/grafanacom.go

@@ -156,8 +156,8 @@ func publishPackages(cfg packaging.PublishConfig) error {
 	pth = path.Join(pth, product)
 	baseArchiveURL := fmt.Sprintf("https://dl.grafana.com/%s", pth)
 
-	var builds []buildRepr
-	for _, ba := range packaging.ArtifactConfigs {
+	builds := make([]buildRepr, len(packaging.ArtifactConfigs))
+	for i, ba := range packaging.ArtifactConfigs {
 		u := ba.GetURL(baseArchiveURL, cfg)
 
 		sha256, err := getSHA256(u)
@@ -165,12 +165,12 @@ func publishPackages(cfg packaging.PublishConfig) error {
 			return err
 		}
 
-		builds = append(builds, buildRepr{
+		builds[i] = buildRepr{
 			OS:     ba.Os,
 			URL:    u,
 			SHA256: string(sha256),
 			Arch:   ba.Arch,
-		})
+		}
 	}
 
 	r := releaseRepr{

pkg/expr/mathexp/exp.go

@@ -558,8 +558,9 @@ func (e *State) biSeriesSeries(labels data.Labels, op string, aSeries, bSeries S
 func (e *State) walkFunc(node *parse.FuncNode) (Results, error) {
 	var res Results
 	var err error
-	var in []reflect.Value
-	for _, a := range node.Args {
+
+	in := make([]reflect.Value, len(node.Args))
+	for i, a := range node.Args {
 		var v any
 		switch t := a.(type) {
 		case *parse.StringNode:
@@ -580,7 +581,8 @@ func (e *State) walkFunc(node *parse.FuncNode) (Results, error) {
 		if err != nil {
 			return res, err
 		}
-		in = append(in, reflect.ValueOf(v))
+
+		in[i] = reflect.ValueOf(v)
 	}
 
 	f := reflect.ValueOf(node.F.F)

pkg/infra/log/log.go

@@ -444,7 +444,7 @@ func ReadLoggingConfig(modes []string, logsPath string, cfg *ini.File) error {
 	defaultLevelName, _ := getLogLevelFromConfig("log", "info", cfg)
 	defaultFilters := getFilters(util.SplitString(cfg.Section("log").Key("filters").String()))
 
-	var configLoggers []logWithFilters
+	configLoggers := make([]logWithFilters, 0, len(modes))
 	for _, mode := range modes {
 		mode = strings.TrimSpace(mode)
 		sec, err := cfg.GetSection("log." + mode)
@@ -505,6 +505,7 @@ func ReadLoggingConfig(modes []string, logsPath string, cfg *ini.File) error {
 
 		handler.filters = modeFilters
 		handler.maxLevel = leveloption
+
 		configLoggers = append(configLoggers, handler)
 	}
 	if len(configLoggers) > 0 {

pkg/modules/modules.go

@@ -71,7 +71,7 @@ func (m *service) Run(ctx context.Context) error {
 		return nil
 	}
 
-	var svcs []services.Service
+	svcs := make([]services.Service, 0, len(m.serviceMap))
 	for _, s := range m.serviceMap {
 		svcs = append(svcs, s)
 	}

pkg/plugins/manager/loader/angular/angularinspector/angularinspector_test.go

@@ -93,6 +93,8 @@ func TestDefaultStaticDetectorsInspector(t *testing.T) {
 		plugin *plugins.Plugin
 		exp    bool
 	}
+
+	//nolint:prealloc // just a test, and it'd require too much refactoring to preallocate
 	var tcs []tc
 
 	// Angular imports

pkg/plugins/manager/signature/manifest_test.go

@@ -381,11 +381,13 @@ func TestFSPathSeparatorFiles(t *testing.T) {
 }
 
 func fileList(manifest *PluginManifest) []string {
-	var keys []string
+	keys := make([]string, 0, len(manifest.Files))
 	for k := range manifest.Files {
 		keys = append(keys, k)
 	}
+
 	sort.Strings(keys)
+
 	return keys
 }
 

pkg/plugins/manager/sources/source_local_disk.go

@@ -62,9 +62,10 @@ func DirAsLocalSources(pluginsPath string, class plugins.Class) ([]*LocalSource,
 	}
 	slices.Sort(pluginDirs)
 
-	var sources []*LocalSource
-	for _, dir := range pluginDirs {
-		sources = append(sources, NewLocalSource(class, []string{dir}))
+	sources := make([]*LocalSource, len(pluginDirs))
+	for i, dir := range pluginDirs {
+		sources[i] = NewLocalSource(class, []string{dir})
 	}
+
 	return sources, nil
 }

pkg/plugins/manager/sources/source_local_disk_test.go

@@ -46,7 +46,7 @@ func TestDirAsLocalSources(t *testing.T) {
 		{
 			name:        "Directory with no subdirectories",
 			pluginsPath: filepath.Join(testdataDir, "pluginRootWithDist", "datasource"),
-			expected:    nil,
+			expected:    []*LocalSource{},
 		},
 		{
 			name:        "Directory with a symlink to a directory",

pkg/plugins/manager/sources/sources.go

@@ -38,22 +38,25 @@ func (s *Service) externalPluginSources() []plugins.PluginSource {
 		return []plugins.PluginSource{}
 	}
 
-	var srcs []plugins.PluginSource
-	for _, src := range localSrcs {
-		srcs = append(srcs, src)
+	srcs := make([]plugins.PluginSource, len(localSrcs))
+	for i, src := range localSrcs {
+		srcs[i] = src
 	}
+
 	return srcs
 }
 
 func (s *Service) pluginSettingSources() []plugins.PluginSource {
-	var sources []plugins.PluginSource
+	sources := make([]plugins.PluginSource, 0, len(s.cfg.PluginSettings))
 	for _, ps := range s.cfg.PluginSettings {
 		path, exists := ps["path"]
 		if !exists || path == "" {
 			continue
 		}
+
 		sources = append(sources, NewLocalSource(plugins.ClassExternal, []string{path}))
 	}
+
 	return sources
 }
 

pkg/plugins/repo/service_test.go

@@ -197,9 +197,8 @@ type versionArg struct {
 }
 
 func createPluginVersions(versions ...versionArg) []Version {
-	var vs []Version
-
-	for _, version := range versions {
+	vs := make([]Version, len(versions))
+	for i, version := range versions {
 		ver := Version{
 			Version: version.version,
 		}
@@ -211,7 +210,8 @@ func createPluginVersions(versions ...versionArg) []Version {
 				}
 			}
 		}
-		vs = append(vs, ver)
+
+		vs[i] = ver
 	}
 
 	return vs

pkg/services/accesscontrol/ossaccesscontrol/permissions_services.go

@@ -326,7 +326,7 @@ func (e DatasourcePermissionsService) SetBuiltInRolePermission(ctx context.Conte
 // if an OSS/unlicensed instance is upgraded to Enterprise/licensed.
 // https://github.com/grafana/identity-access-team/issues/672
 func (e DatasourcePermissionsService) SetPermissions(ctx context.Context, orgID int64, resourceID string, commands ...accesscontrol.SetResourcePermissionCommand) ([]accesscontrol.ResourcePermission, error) {
-	var dbCommands []resourcepermissions.SetResourcePermissionsCommand
+	dbCommands := make([]resourcepermissions.SetResourcePermissionsCommand, 0, len(commands))
 	for _, cmd := range commands {
 		// Only set query permissions for built-in roles; do not set permissions for data sources with * as UID, as this would grant wildcard permissions
 		if cmd.Permission != "Query" || cmd.BuiltinRole == "" || resourceID == "*" {

pkg/services/cloudmigration/cloudmigrationimpl/cloudmigration.go

@@ -420,13 +420,31 @@ func (s *Service) RunMigration(ctx context.Context, uid string) (*cloudmigration
 }
 
 func (s *Service) getMigrationDataJSON(ctx context.Context) (*cloudmigration.MigrateDataRequest, error) {
-	var migrationDataSlice []cloudmigration.MigrateDataRequestItem
 	// Data sources
 	dataSources, err := s.getDataSources(ctx)
 	if err != nil {
 		s.log.Error("Failed to get datasources", "err", err)
 		return nil, err
 	}
+
+	// Dashboards
+	dashboards, err := s.getDashboards(ctx)
+	if err != nil {
+		s.log.Error("Failed to get dashboards", "err", err)
+		return nil, err
+	}
+
+	// Folders
+	folders, err := s.getFolders(ctx)
+	if err != nil {
+		s.log.Error("Failed to get folders", "err", err)
+		return nil, err
+	}
+
+	migrationDataSlice := make(
+		[]cloudmigration.MigrateDataRequestItem, 0,
+		len(dataSources)+len(dashboards)+len(folders),
+	)
 	for _, ds := range dataSources {
 		migrationDataSlice = append(migrationDataSlice, cloudmigration.MigrateDataRequestItem{
 			Type:  cloudmigration.DatasourceDataType,
@@ -436,13 +454,6 @@ func (s *Service) getMigrationDataJSON(ctx context.Context) (*cloudmigration.Mig
 		})
 	}
 
-	// Dashboards
-	dashboards, err := s.getDashboards(ctx)
-	if err != nil {
-		s.log.Error("Failed to get dashboards", "err", err)
-		return nil, err
-	}
-
 	for _, dashboard := range dashboards {
 		dashboard.Data.Del("id")
 		migrationDataSlice = append(migrationDataSlice, cloudmigration.MigrateDataRequestItem{
@@ -453,13 +464,6 @@ func (s *Service) getMigrationDataJSON(ctx context.Context) (*cloudmigration.Mig
 		})
 	}
 
-	// Folders
-	folders, err := s.getFolders(ctx)
-	if err != nil {
-		s.log.Error("Failed to get folders", "err", err)
-		return nil, err
-	}
-
 	for _, f := range folders {
 		migrationDataSlice = append(migrationDataSlice, cloudmigration.MigrateDataRequestItem{
 			Type:  cloudmigration.FolderDataType,
@@ -468,6 +472,7 @@ func (s *Service) getMigrationDataJSON(ctx context.Context) (*cloudmigration.Mig
 			Data:  f,
 		})
 	}
+
 	migrationData := &cloudmigration.MigrateDataRequest{
 		Items: migrationDataSlice,
 	}
@@ -521,9 +526,9 @@ func (s *Service) getFolders(ctx context.Context) ([]folder.Folder, error) {
 		return nil, err
 	}
 
-	var result []folder.Folder
-	for _, folder := range folders {
-		result = append(result, *folder)
+	result := make([]folder.Folder, len(folders))
+	for i, folder := range folders {
+		result[i] = *folder
 	}
 
 	return result, nil
@@ -535,10 +540,11 @@ func (s *Service) getDashboards(ctx context.Context) ([]dashboards.Dashboard, er
 		return nil, err
 	}
 
-	var result []dashboards.Dashboard
-	for _, dashboard := range dashs {
-		result = append(result, *dashboard)
+	result := make([]dashboards.Dashboard, len(dashs))
+	for i, dashboard := range dashs {
+		result[i] = *dashboard
 	}
+
 	return result, nil
 }
 

pkg/services/live/live.go

@@ -332,12 +332,14 @@ func setupRedisLiveEngine(g *GrafanaLive, node *centrifuge.Node) error {
 	redisShardConfigs := []centrifuge.RedisShardConfig{
 		{Address: redisAddress, Password: redisPassword},
 	}
-	var redisShards []*centrifuge.RedisShard
+
+	redisShards := make([]*centrifuge.RedisShard, 0, len(redisShardConfigs))
 	for _, redisConf := range redisShardConfigs {
 		redisShard, err := centrifuge.NewRedisShard(node, redisConf)
 		if err != nil {
 			return fmt.Errorf("error connecting to Live Redis: %v", err)
 		}
+
 		redisShards = append(redisShards, redisShard)
 	}
 
@@ -348,6 +350,7 @@ func setupRedisLiveEngine(g *GrafanaLive, node *centrifuge.Node) error {
 	if err != nil {
 		return fmt.Errorf("error creating Live Redis broker: %v", err)
 	}
+
 	node.SetBroker(broker)
 
 	presenceManager, err := centrifuge.NewRedisPresenceManager(node, centrifuge.RedisPresenceManagerConfig{
@@ -357,7 +360,9 @@ func setupRedisLiveEngine(g *GrafanaLive, node *centrifuge.Node) error {
 	if err != nil {
 		return fmt.Errorf("error creating Live Redis presence manager: %v", err)
 	}
+
 	node.SetPresenceManager(presenceManager)
+
 	return nil
 }
 

pkg/services/live/runstream/manager.go

@@ -116,17 +116,21 @@ func (s *Manager) handleDatasourceEvent(orgID int64, dsUID string, resubmit bool
 		s.mu.RUnlock()
 		return nil
 	}
-	var resubmitRequests []streamRequest
-	var waitChannels []chan struct{}
+
+	resubmitRequests := make([]streamRequest, 0, len(dsStreams))
+	waitChannels := make([]chan struct{}, 0, len(dsStreams))
 	for channel := range dsStreams {
 		streamCtx, ok := s.streams[channel]
 		if !ok {
 			continue
 		}
+
 		streamCtx.cancelFn()
+
 		waitChannels = append(waitChannels, streamCtx.CloseCh)
 		resubmitRequests = append(resubmitRequests, streamCtx.streamRequest)
 	}
+
 	s.mu.RUnlock()
 
 	// Wait for all streams to stop.

pkg/services/ngalert/api/api_prometheus.go

@@ -563,8 +563,8 @@ func toRuleGroup(log log.Logger, manager state.AlertInstanceManager, groupKey ng
 // Returns the whole JSON model as a string if it fails to extract a minimum of 1 query.
 func ruleToQuery(logger log.Logger, rule *ngmodels.AlertRule) string {
 	var queryErr error
-	var queries []string
 
+	queries := make([]string, 0, len(rule.Data))
 	for _, q := range rule.Data {
 		q, err := q.GetQuery()
 		if err != nil {

pkg/services/ngalert/api/compat_contact_points.go

@@ -46,156 +46,164 @@ func ContactPointToContactPointExport(cp definitions.ContactPoint) (notify.APIRe
 	// This is needed to keep the API models clean and convert from database model
 	j.RegisterExtension(&contactPointsExtension{})
 
-	var integration []*notify.GrafanaIntegrationConfig
+	contactPointsLength := len(cp.Alertmanager) + len(cp.Dingding) + len(cp.Discord) + len(cp.Email) +
+		len(cp.Googlechat) + len(cp.Kafka) + len(cp.Line) + len(cp.Opsgenie) +
+		len(cp.Pagerduty) + len(cp.OnCall) + len(cp.Pushover) + len(cp.Sensugo) +
+		len(cp.Sns) + len(cp.Slack) + len(cp.Teams) + len(cp.Telegram) +
+		len(cp.Threema) + len(cp.Victorops) + len(cp.Webhook) + len(cp.Wecom) +
+		len(cp.Webex)
+
+	integration := make([]*notify.GrafanaIntegrationConfig, 0, contactPointsLength)
 
 	var errs []error
 	for _, i := range cp.Alertmanager {
 		el, err := marshallIntegration(j, "prometheus-alertmanager", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Dingding {
 		el, err := marshallIntegration(j, "dingding", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Discord {
 		el, err := marshallIntegration(j, "discord", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Email {
 		el, err := marshallIntegration(j, "email", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Googlechat {
 		el, err := marshallIntegration(j, "googlechat", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Kafka {
 		el, err := marshallIntegration(j, "kafka", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Line {
 		el, err := marshallIntegration(j, "line", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Opsgenie {
 		el, err := marshallIntegration(j, "opsgenie", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Pagerduty {
 		el, err := marshallIntegration(j, "pagerduty", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.OnCall {
 		el, err := marshallIntegration(j, "oncall", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Pushover {
 		el, err := marshallIntegration(j, "pushover", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Sensugo {
 		el, err := marshallIntegration(j, "sensugo", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Sns {
 		el, err := marshallIntegration(j, "sns", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Slack {
 		el, err := marshallIntegration(j, "slack", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Teams {
 		el, err := marshallIntegration(j, "teams", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Telegram {
 		el, err := marshallIntegration(j, "telegram", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Threema {
 		el, err := marshallIntegration(j, "threema", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Victorops {
 		el, err := marshallIntegration(j, "victorops", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Webhook {
 		el, err := marshallIntegration(j, "webhook", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Wecom {
 		el, err := marshallIntegration(j, "wecom", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
 	for _, i := range cp.Webex {
 		el, err := marshallIntegration(j, "webex", i, i.DisableResolveMessage)
-		integration = append(integration, el)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		integration = append(integration, el)
 	}
+
 	if len(errs) > 0 {
 		return notify.APIReceiver{}, errors.Join(errs...)
 	}

pkg/services/ngalert/provisioning/contactpoints.go

@@ -88,13 +88,14 @@ func (ecp *ContactPointService) GetContactPoints(ctx context.Context, q ContactP
 		}
 	}
 
-	var contactPoints []apimodels.EmbeddedContactPoint
-	for _, gr := range grafanaReceivers {
+	contactPoints := make([]apimodels.EmbeddedContactPoint, len(grafanaReceivers))
+	for i, gr := range grafanaReceivers {
 		contactPoint, err := GettableGrafanaReceiverToEmbeddedContactPoint(gr)
 		if err != nil {
 			return nil, err
 		}
-		contactPoints = append(contactPoints, contactPoint)
+
+		contactPoints[i] = contactPoint
 	}
 
 	sort.SliceStable(contactPoints, func(i, j int) bool {

pkg/services/ngalert/provisioning/templates.go

@@ -31,17 +31,19 @@ func (t *TemplateService) GetTemplates(ctx context.Context, orgID int64) ([]defi
 		return nil, err
 	}
 
-	var templates []definitions.NotificationTemplate
+	templates := make([]definitions.NotificationTemplate, 0, len(revision.cfg.TemplateFiles))
 	for name, tmpl := range revision.cfg.TemplateFiles {
 		tmpl := definitions.NotificationTemplate{
 			Name:     name,
 			Template: tmpl,
 		}
+
 		provenance, err := t.provenanceStore.GetProvenance(ctx, &tmpl, orgID)
 		if err != nil {
 			return nil, err
 		}
 		tmpl.Provenance = definitions.Provenance(provenance)
+
 		templates = append(templates, tmpl)
 	}
 

pkg/services/ngalert/remote/alertmanager.go

@@ -492,13 +492,14 @@ func (am *Alertmanager) GetReceivers(ctx context.Context) ([]apimodels.Receiver,
 		return []apimodels.Receiver{}, err
 	}
 
-	var rcvs []apimodels.Receiver
-	for _, rcv := range res.Payload {
-		rcvs = append(rcvs, apimodels.Receiver{
+	rcvs := make([]apimodels.Receiver, len(res.Payload))
+	for i, rcv := range res.Payload {
+		rcvs[i] = apimodels.Receiver{
 			Name:         *rcv.Name,
 			Integrations: []apimodels.Integration{},
-		})
 		}
+	}
+
 	return rcvs, nil
 }
 

pkg/services/ngalert/sender/router.go

@@ -205,15 +205,17 @@ func (d *AlertsRouter) SyncAndApplyConfigFromDatabase(ctx context.Context) error
 }
 
 func buildRedactedAMs(l log.Logger, alertmanagers []ExternalAMcfg, ordId int64) []string {
-	var redactedAMs []string
+	redactedAMs := make([]string, 0, len(alertmanagers))
 	for _, am := range alertmanagers {
 		parsedAM, err := url.Parse(am.URL)
 		if err != nil {
 			l.Error("Failed to parse alertmanager string", "org", ordId, "error", err)
 			continue
 		}
+
 		redactedAMs = append(redactedAMs, parsedAM.Redacted())
 	}
+
 	return redactedAMs
 }
 
@@ -225,9 +227,6 @@ func asSHA256(strings []string) string {
 }
 
 func (d *AlertsRouter) alertmanagersFromDatasources(orgID int64) ([]ExternalAMcfg, error) {
-	var (
-		alertmanagers []ExternalAMcfg
-	)
 	// We might have alertmanager datasources that are acting as external
 	// alertmanager, let's fetch them.
 	query := &datasources.GetDataSourcesByTypeQuery{
@@ -240,6 +239,9 @@ func (d *AlertsRouter) alertmanagersFromDatasources(orgID int64) ([]ExternalAMcf
 	if err != nil {
 		return nil, fmt.Errorf("failed to fetch datasources for org: %w", err)
 	}
+
+	alertmanagers := make([]ExternalAMcfg, 0, len(dataSources))
+
 	for _, ds := range dataSources {
 		if !ds.JsonData.Get(definitions.HandleGrafanaManagedAlerts).MustBool(false) {
 			continue
@@ -262,11 +264,13 @@ func (d *AlertsRouter) alertmanagersFromDatasources(orgID int64) ([]ExternalAMcf
 				"error", err)
 			continue
 		}
+
 		alertmanagers = append(alertmanagers, ExternalAMcfg{
 			URL:     amURL,
 			Headers: headers,
 		})
 	}
+
 	return alertmanagers, nil
 }
 

pkg/services/ngalert/sender/router_test.go

@@ -712,7 +712,7 @@ func TestAlertManagers_buildRedactedAMs(t *testing.T) {
 			amUrls:   []string{"1234://user:password@localhost:9094"},
 			errCalls: 1,
 			errLog:   "Failed to parse alertmanager string",
-			expected: nil,
+			expected: []string{},
 		},
 	}
 
@@ -724,6 +724,7 @@ func TestAlertManagers_buildRedactedAMs(t *testing.T) {
 					URL: url,
 				})
 			}
+
 			require.Equal(t, tt.expected, buildRedactedAMs(&fakeLogger, cfgs, tt.orgId))
 			require.Equal(t, tt.errCalls, fakeLogger.ErrorLogs.Calls)
 			require.Equal(t, tt.errLog, fakeLogger.ErrorLogs.Message)

pkg/services/ngalert/state/compat.go

@@ -141,9 +141,9 @@ func errorAlert(labels, annotations data.Labels, alertState *State, urlStr strin
 
 func FromStateTransitionToPostableAlerts(firingStates []StateTransition, stateManager *Manager, appURL *url.URL) apimodels.PostableAlerts {
 	alerts := apimodels.PostableAlerts{PostableAlerts: make([]models.PostableAlert, 0, len(firingStates))}
-	var sentAlerts []*State
 	ts := time.Now()
 
+	sentAlerts := make([]*State, 0, len(firingStates))
 	for _, alertState := range firingStates {
 		if !alertState.NeedsSending(stateManager.ResendDelay) {
 			continue

pkg/services/ngalert/store/alert_rule.go

@@ -787,7 +787,8 @@ func (st DBstore) RenameReceiverInNotificationSettings(ctx context.Context, orgI
 	if len(rules) == 0 {
 		return 0, nil
 	}
-	var updates []ngmodels.UpdateRule
+
+	updates := make([]ngmodels.UpdateRule, 0, len(rules))
 	for _, rule := range rules {
 		r := ngmodels.CopyRule(rule)
 		for idx := range r.NotificationSettings {
@@ -795,6 +796,7 @@ func (st DBstore) RenameReceiverInNotificationSettings(ctx context.Context, orgI
 				r.NotificationSettings[idx].Receiver = newReceiver
 			}
 		}
+
 		updates = append(updates, ngmodels.UpdateRule{
 			Existing: rule,
 			New:      *r,

pkg/services/plugindashboards/service/dashboard_updater_test.go

@@ -401,15 +401,15 @@ type pluginsSettingsServiceMock struct {
 func (s *pluginsSettingsServiceMock) GetPluginSettings(_ context.Context, args *pluginsettings.GetArgs) ([]*pluginsettings.InfoDTO, error) {
 	s.getPluginSettingsArgs = append(s.getPluginSettingsArgs, args.OrgID)
 
-	var res []*pluginsettings.InfoDTO
-	for _, ps := range s.storedPluginSettings {
-		res = append(res, &pluginsettings.InfoDTO{
+	res := make([]*pluginsettings.InfoDTO, len(s.storedPluginSettings))
+	for i, ps := range s.storedPluginSettings {
+		res[i] = &pluginsettings.InfoDTO{
 			PluginID:      ps.PluginID,
 			OrgID:         ps.OrgID,
 			Enabled:       ps.Enabled,
 			Pinned:        ps.Pinned,
 			PluginVersion: ps.PluginVersion,
-		})
+		}
 	}
 
 	return res, s.err

pkg/services/pluginsintegration/pluginconfig/envvars.go

@@ -163,17 +163,23 @@ func (p *EnvVarsProvider) tracingEnvVars(plugin *plugins.Plugin) []string {
 
 func (p *EnvVarsProvider) pluginSettingsEnvVars(pluginID string) []string {
 	const customConfigPrefix = "GF_PLUGIN"
-	var env []string
-	for k, v := range p.cfg.PluginSettings[pluginID] {
+
+	pluginSettings := p.cfg.PluginSettings[pluginID]
+
+	env := make([]string, 0, len(pluginSettings))
+	for k, v := range pluginSettings {
 		if k == "path" || strings.ToLower(k) == "id" {
 			continue
 		}
+
 		key := fmt.Sprintf("%s_%s", customConfigPrefix, strings.ToUpper(k))
 		if value := os.Getenv(key); value != "" {
 			v = value
 		}
+
 		env = append(env, fmt.Sprintf("%s=%s", key, v))
 	}
+
 	return env
 }
 

pkg/services/searchV2/bluge.go

@@ -191,7 +191,9 @@ func getNonFolderDashboardDoc(dash dashboard, location string) *bluge.Document {
 func getDashboardPanelDocs(dash dashboard, location string) []*bluge.Document {
 	dashURL := fmt.Sprintf("/d/%s/%s", dash.uid, slugify.Slugify(dash.summary.Name))
 
-	var docs []*bluge.Document
+	// pre-allocating a little bit more than necessary, possibly
+	docs := make([]*bluge.Document, 0, len(dash.summary.Nested))
+
 	for _, panel := range dash.summary.Nested {
 		if panel.Fields["type"] == "row" {
 			continue // skip rows
@@ -239,7 +241,7 @@ func getDashboardPanelDocs(dash dashboard, location string) []*bluge.Document {
 }
 
 // Names need to be indexed a few ways to support key features
-func newSearchDocument(uid string, name string, descr string, url string) *bluge.Document {
+func newSearchDocument(uid, name, descr, url string) *bluge.Document {
 	doc := bluge.NewDocument(uid)
 
 	if name != "" {

pkg/services/searchV2/ngram_test.go

@@ -51,9 +51,11 @@ func Test_punctuationCharFilter_Filter(t1 *testing.T) {
 func TestNgramIndexAnalyzer(t *testing.T) {
 	stream := ngramIndexAnalyzer.Analyze([]byte("x-rays.and.xRays, and НемногоКириллицы"))
 	expectedTerms := []string{"x", "r", "ra", "ray", "rays", "a", "an", "and", "x", "r", "ra", "ray", "rays", "a", "an", "and", "н", "не", "нем", "немн", "немно", "немног", "немного", "к", "ки", "кир", "кири", "кирил", "кирилл", "кирилли"}
-	var actualTerms []string
+
+	actualTerms := make([]string, 0, len(stream))
 	for _, t := range stream {
 		actualTerms = append(actualTerms, string(t.Term))
 	}
+
 	require.Equal(t, expectedTerms, actualTerms)
 }

pkg/services/sqlstore/migrations/external_alertmanagers.go

@@ -97,9 +97,8 @@ func (e externalAlertmanagerToDatasources) Exec(sess *xorm.Session, mg *migrator
 }
 
 func removeDuplicates(strs []string) []string {
-	var res []string
-	found := map[string]bool{}
-
+	found := make(map[string]bool, len(strs))
+	res := make([]string, 0, len(strs))
 	for _, str := range strs {
 		if found[str] {
 			continue

pkg/services/sqlstore/permissions/dashboard.go

@@ -435,8 +435,10 @@ func (f *accessControlDashboardPermissionFilter) nestedFoldersSelectors(permSele
 }
 
 func getAllowedUIDs(action string, user identity.Requester, scopePrefix string) []any {
-	var args []any
-	for _, uidScope := range user.GetPermissions()[action] {
+	uidScopes := user.GetPermissions()[action]
+
+	args := make([]any, 0, len(uidScopes))
+	for _, uidScope := range uidScopes {
 		if !strings.HasPrefix(uidScope, scopePrefix) {
 			continue
 		}

pkg/services/ssosettings/api/api.go

@@ -101,7 +101,7 @@ func (api *Api) getAuthorizedList(ctx context.Context, identity identity.Request
 		return nil, err
 	}
 
-	var authorizedProviders []*models.SSOSettings
+	authorizedProviders := make([]*models.SSOSettings, 0, len(allProviders))
 	for _, provider := range allProviders {
 		ev := ac.EvalPermission(ac.ActionSettingsRead, ac.Scope("settings", "auth."+provider.Provider, "*"))
 		hasAccess, err := api.AccessControl.Evaluate(ctx, identity, ev)

pkg/setting/setting.go

@@ -1986,19 +1986,23 @@ func (cfg *Cfg) readLiveSettings(iniFile *ini.File) error {
 	cfg.LiveHAEngineAddress = section.Key("ha_engine_address").MustString("127.0.0.1:6379")
 	cfg.LiveHAEnginePassword = section.Key("ha_engine_password").MustString("")
 
-	var originPatterns []string
 	allowedOrigins := section.Key("allowed_origins").MustString("")
-	for _, originPattern := range strings.Split(allowedOrigins, ",") {
+	origins := strings.Split(allowedOrigins, ",")
+
+	originPatterns := make([]string, 0, len(origins))
+	for _, originPattern := range origins {
 		originPattern = strings.TrimSpace(originPattern)
 		if originPattern == "" {
 			continue
 		}
 		originPatterns = append(originPatterns, originPattern)
 	}
+
 	_, err := GetAllowedOriginGlobs(originPatterns)
 	if err != nil {
 		return err
 	}
+
 	cfg.LiveAllowedOrigins = originPatterns
 	return nil
 }

pkg/setting/setting_secure_socks_proxy.go

@@ -75,7 +75,7 @@ func readSecureSocksDSProxySettings(iniFile *ini.File) (SecureSocksDSProxySettin
 		s.ClientKey = string(keyPEMBlock)
 	}
 
-	var rootCAs []string
+	rootCAs := make([]string, 0, len(s.RootCAFilePaths))
 	for _, rootCAFile := range s.RootCAFilePaths {
 		// nolint:gosec
 		// The gosec G304 warning can be ignored because `rootCAFile` comes from config ini, and we check below if

pkg/tsdb/azuremonitor/resourcegraph/azure-resource-graph-datasource.go

@@ -88,9 +88,8 @@ type argJSONQuery struct {
 }
 
 func (e *AzureResourceGraphDatasource) buildQueries(queries []backend.DataQuery, dsInfo types.DatasourceInfo) ([]*AzureResourceGraphQuery, error) {
-	var azureResourceGraphQueries []*AzureResourceGraphQuery
-
-	for _, query := range queries {
+	azureResourceGraphQueries := make([]*AzureResourceGraphQuery, len(queries))
+	for i, query := range queries {
 		queryJSONModel := argJSONQuery{}
 		err := json.Unmarshal(query.JSON, &queryJSONModel)
 		if err != nil {
@@ -105,19 +104,18 @@ func (e *AzureResourceGraphDatasource) buildQueries(queries []backend.DataQuery,
 		}
 
 		interpolatedQuery, err := macros.KqlInterpolate(query, dsInfo, azureResourceGraphTarget.Query)
-
 		if err != nil {
 			return nil, err
 		}
 
-		azureResourceGraphQueries = append(azureResourceGraphQueries, &AzureResourceGraphQuery{
+		azureResourceGraphQueries[i] = &AzureResourceGraphQuery{
 			RefID:             query.RefID,
 			ResultFormat:      resultFormat,
 			JSON:              query.JSON,
 			InterpolatedQuery: interpolatedQuery,
 			TimeRange:         query.TimeRange,
 			QueryType:         query.QueryType,
-		})
+		}
 	}
 
 	return azureResourceGraphQueries, nil

pkg/tsdb/azuremonitor/types/types.go

@@ -129,8 +129,8 @@ type AzureMonitorDimensionFilterBackend struct {
 }
 
 func ConstructFiltersString(a dataquery.AzureMetricDimension) string {
-	var filterStrings []string
-	for _, filter := range a.Filters {
+	filterStrings := make([]string, len(a.Filters))
+	for i, filter := range a.Filters {
 		dimension := ""
 		operator := ""
 		if a.Dimension != nil {
@@ -139,11 +139,14 @@ func ConstructFiltersString(a dataquery.AzureMetricDimension) string {
 		if a.Operator != nil {
 			operator = *a.Operator
 		}
-		filterStrings = append(filterStrings, fmt.Sprintf("%v %v '%v'", dimension, operator, filter))
+
+		filterStrings[i] = fmt.Sprintf("%v %v '%v'", dimension, operator, filter)
 	}
+
 	if a.Operator != nil && *a.Operator == "eq" {
 		return strings.Join(filterStrings, " or ")
 	}
+
 	return strings.Join(filterStrings, " and ")
 }
 

pkg/tsdb/cloudwatch/services/utils.go

@@ -7,7 +7,7 @@ import (
 )
 
 func valuesToListMetricRespone[T any](values []T) []resources.ResourceResponse[T] {
-	var response []resources.ResourceResponse[T]
+	response := make([]resources.ResourceResponse[T], 0, len(values))
 	for _, value := range values {
 		response = append(response, resources.ResourceResponse[T]{Value: value})
 	}

pkg/tsdb/elasticsearch/querydata_test.go

@@ -84,15 +84,16 @@ func newFlowTestQueries(allJsonBytes []byte) ([]backend.DataQuery, error) {
 		return nil, fmt.Errorf("error unmarshaling query-json: %w", err)
 	}
 
-	var queries []backend.DataQuery
-
-	for _, jsonBytes := range jsonBytesArray {
+	queries := make([]backend.DataQuery, len(jsonBytesArray))
+	for i, jsonBytes := range jsonBytesArray {
 		// we need to extract some fields from the json-array
 		var jsonInfo queryDataTestQueryJSON
+
 		err = json.Unmarshal(jsonBytes, &jsonInfo)
 		if err != nil {
 			return nil, err
 		}
+
 		// we setup the DataQuery, with values loaded from the json
 		query := backend.DataQuery{
 			RefID:         jsonInfo.RefID,
@@ -101,7 +102,8 @@ func newFlowTestQueries(allJsonBytes []byte) ([]backend.DataQuery, error) {
 			TimeRange:     timeRange,
 			JSON:          jsonBytes,
 		}
-		queries = append(queries, query)
+
+		queries[i] = query
 	}
 	return queries, nil
 }

pkg/tsdb/elasticsearch/response_parser.go

@@ -873,16 +873,16 @@ func trimDatapoints(queryResult backend.DataResponse, target *Query) {
 // we sort the label's pairs by the label-key,
 // and return the label-values
 func getSortedLabelValues(labels data.Labels) []string {
-	var keys []string
+	keys := make([]string, 0, len(labels))
 	for key := range labels {
 		keys = append(keys, key)
 	}
 
 	sort.Strings(keys)
 
-	var values []string
-	for _, key := range keys {
-		values = append(values, labels[key])
+	values := make([]string, len(keys))
+	for i, key := range keys {
+		values[i] = labels[key]
 	}
 
 	return values

pkg/tsdb/influxdb/fsql/arrow_test.go

@@ -60,7 +60,7 @@ func TestNewQueryDataResponse(t *testing.T) {
 		newJSONArray(`[0, 1, 2]`, &arrow.TimestampType{}),
 	}
 
-	var arr []arrow.Array
+	arr := make([]arrow.Array, 0, len(strValues))
 	for _, v := range strValues {
 		tarr, _, err := array.FromJSON(
 			alloc,

pkg/tsdb/influxdb/influxql/buffered/response_parser.go

@@ -269,12 +269,12 @@ func transformRowsForTimeSeries(rows []models.Row, query models.Query) data.Fram
 }
 
 func newFrameWithTimeField(row models.Row, column string, colIndex int, query models.Query, frameName []byte) *data.Frame {
-	var timeArray []time.Time
 	var floatArray []*float64
 	var stringArray []*string
 	var boolArray []*bool
 	valType := util.Typeof(row.Values, colIndex)
 
+	timeArray := make([]time.Time, 0, len(row.Values))
 	for _, valuePair := range row.Values {
 		timestamp, timestampErr := util.ParseTimestamp(valuePair[0])
 		// we only add this row if the timestamp is valid

pkg/tsdb/tempo/trace_transform_test.go

@@ -136,10 +136,11 @@ func rootSpan(frame *BetterFrame) Row {
 }
 
 func fieldNames(frame *data.Frame) []string {
-	var names []string
-	for _, f := range frame.Fields {
-		names = append(names, f.Name)
+	names := make([]string, len(frame.Fields))
+	for i, f := range frame.Fields {
+		names[i] = f.Name
 	}
+
 	return names
 }
 

pkg/util/strings.go

@@ -48,11 +48,13 @@ func SplitString(str string) []string {
 		return res
 	}
 
-	var result []string
 	matches := stringListItemMatcher.FindAllString(str, -1)
-	for _, match := range matches {
-		result = append(result, strings.Trim(match, "\""))
+
+	result := make([]string, len(matches))
+	for i, match := range matches {
+		result[i] = strings.Trim(match, "\"")
 	}
+
 	return result
 }
 

pkg/util/tls.go

@@ -30,22 +30,26 @@ func TlsCiphersToIDs(names []string) ([]uint16, error) {
 		// no ciphers specified, use defaults
 		return nil, nil
 	}
-	var ids []uint16
-	var missing []string
 
 	ciphers := tls.CipherSuites()
-	var cipherMap = make(map[string]uint16, len(ciphers))
+
+	cipherMap := make(map[string]uint16, len(ciphers))
 	for _, cipher := range ciphers {
 		cipherMap[cipher.Name] = cipher.ID
 	}
 
+	missing := []string{}
+	ids := make([]uint16, 0, len(names))
+
 	for _, name := range names {
 		name = strings.ToUpper(name)
+
 		id, ok := cipherMap[name]
 		if !ok {
 			missing = append(missing, name)
 			continue
 		}
+
 		ids = append(ids, id)
 	}