Make selector string casing configurable (elastic#18854)

Add support for configuring the string casing in the index/pipeline/key/topic 'Selector'. 

## Why is it important?

Elasticsearch pipeline and index names are required to be lower case only. When used with fields from events this was not always guaranteed, leading us to enforce lower case always (elastic#16081. elastic#6342).
As the code is reused for Kafka topic selection, this unfortunately did lead to a Regression as some users expect strings to allow mixed case (elastic#18640).
With this PR Elasticsearch related resources (e.g. index or pipeline names) are set to lowercase only, while not touching the strings in other outputs.

CHANGELOG.next.asciidoc

@@ -124,6 +124,8 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Fix the `translate_sid` processor's handling of unconfigured target fields. {issue}18990[18990] {pull}18991[18991]
 - Fixed a service restart failure under Windows. {issue}18914[18914] {pull}18916[18916]
 - The `monitoring.elasticsearch.api_key` value is correctly base64-encoded before being sent to the monitoring Elasticsearch cluster. {issue}18939[18939] {pull}18945[18945]
+- Fix kafka topic setting not allowing upper case characters. {pull}18854[18854] {issue}18640[18640]
+- Fix redis key setting not allowing upper case characters. {pull}18854[18854] {issue}18640[18640]
 
 *Auditbeat*
 

libbeat/idxmgmt/std.go

@@ -20,6 +20,7 @@ package idxmgmt
 import (
 	"errors"
 	"fmt"
+	"strings"
 
 	"github.com/elastic/beats/v7/libbeat/beat"
 	"github.com/elastic/beats/v7/libbeat/beat/events"
@@ -198,6 +199,7 @@ func (s *indexSupport) BuildSelector(cfg *common.Config) (outputs.IndexSelector,
 		MultiKey:         "indices",
 		EnableSingleOnly: true,
 		FailEmpty:        mode != ilm.ModeEnabled,
+		Case:             outil.SelectorLowerCase,
 	}
 
 	indexSel, err := outil.BuildSelectorFromConfig(selCfg, buildSettings)
@@ -354,21 +356,21 @@ func getEventCustomIndex(evt *beat.Event, beatInfo beat.Info) string {
 	}
 
 	if alias, err := events.GetMetaStringValue(*evt, events.FieldMetaAlias); err == nil {
-		return alias
+		return strings.ToLower(alias)
 	}
 
 	if idx, err := events.GetMetaStringValue(*evt, events.FieldMetaIndex); err == nil {
 		ts := evt.Timestamp.UTC()
 		return fmt.Sprintf("%s-%d.%02d.%02d",
-			idx, ts.Year(), ts.Month(), ts.Day())
+			strings.ToLower(idx), ts.Year(), ts.Month(), ts.Day())
 	}
 
 	// This is functionally identical to Meta["alias"], returning the overriding
 	// metadata as the index name if present. It is currently used by Filebeat
 	// to send the index for particular inputs to formatted string templates,
 	// which are then expanded by a processor to the "raw_index" field.
 	if idx, err := events.GetMetaStringValue(*evt, events.FieldMetaRawIndex); err == nil {
-		return idx
+		return strings.ToLower(idx)
 	}
 
 	return ""

libbeat/idxmgmt/std_test.go

@@ -139,6 +139,11 @@ func TestDefaultSupport_BuildSelector(t *testing.T) {
 			cfg:      map[string]interface{}{"index": "test-%{[agent.version]}"},
 			want:     stable("test-9.9.9"),
 		},
+		"without ilm must be lowercase": {
+			ilmCalls: noILM,
+			cfg:      map[string]interface{}{"index": "TeSt-%{[agent.version]}"},
+			want:     stable("test-9.9.9"),
+		},
 		"event alias without ilm": {
 			ilmCalls: noILM,
 			cfg:      map[string]interface{}{"index": "test-%{[agent.version]}"},
@@ -147,6 +152,14 @@ func TestDefaultSupport_BuildSelector(t *testing.T) {
 				"alias": "test",
 			},
 		},
+		"event alias without ilm must be lowercae": {
+			ilmCalls: noILM,
+			cfg:      map[string]interface{}{"index": "test-%{[agent.version]}"},
+			want:     stable("test"),
+			meta: common.MapStr{
+				"alias": "Test",
+			},
+		},
 		"event index without ilm": {
 			ilmCalls: noILM,
 			cfg:      map[string]interface{}{"index": "test-%{[agent.version]}"},
@@ -155,11 +168,24 @@ func TestDefaultSupport_BuildSelector(t *testing.T) {
 				"index": "test",
 			},
 		},
+		"event index without ilm must be lowercase": {
+			ilmCalls: noILM,
+			cfg:      map[string]interface{}{"index": "test-%{[agent.version]}"},
+			want:     dateIdx("test"),
+			meta: common.MapStr{
+				"index": "Test",
+			},
+		},
 		"with ilm": {
 			ilmCalls: ilmTemplateSettings("test-9.9.9", "test-9.9.9"),
 			cfg:      map[string]interface{}{"index": "wrong-%{[agent.version]}"},
 			want:     stable("test-9.9.9"),
 		},
+		"with ilm must be lowercase": {
+			ilmCalls: ilmTemplateSettings("Test-9.9.9", "Test-9.9.9"),
+			cfg:      map[string]interface{}{"index": "wrong-%{[agent.version]}"},
+			want:     stable("test-9.9.9"),
+		},
 		"event alias wit ilm": {
 			ilmCalls: ilmTemplateSettings("test-9.9.9", "test-9.9.9"),
 			cfg:      map[string]interface{}{"index": "test-%{[agent.version]}"},
@@ -168,6 +194,14 @@ func TestDefaultSupport_BuildSelector(t *testing.T) {
 				"alias": "event-alias",
 			},
 		},
+		"event alias wit ilm must be lowercase": {
+			ilmCalls: ilmTemplateSettings("test-9.9.9", "test-9.9.9"),
+			cfg:      map[string]interface{}{"index": "test-%{[agent.version]}"},
+			want:     stable("event-alias"),
+			meta: common.MapStr{
+				"alias": "Event-alias",
+			},
+		},
 		"event index with ilm": {
 			ilmCalls: ilmTemplateSettings("test-9.9.9", "test-9.9.9"),
 			cfg:      map[string]interface{}{"index": "test-%{[agent.version]}"},
@@ -186,6 +220,16 @@ func TestDefaultSupport_BuildSelector(t *testing.T) {
 			},
 			want: stable("myindex"),
 		},
+		"use indices settings must be lowercase": {
+			ilmCalls: ilmTemplateSettings("test-9.9.9", "test-9.9.9"),
+			cfg: map[string]interface{}{
+				"index": "test-%{[agent.version]}",
+				"indices": []map[string]interface{}{
+					{"index": "MyIndex"},
+				},
+			},
+			want: stable("myindex"),
+		},
 	}
 	for name, test := range cases {
 		t.Run(name, func(t *testing.T) {

libbeat/outputs/elasticsearch/client.go

@@ -22,6 +22,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"strings"
 	"time"
 
 	"go.elastic.co/apm"
@@ -356,7 +357,7 @@ func getPipeline(event *beat.Event, pipelineSel *outil.Selector) (string, error)
 			return "", errors.New("pipeline metadata is no string")
 		}
 
-		return pipeline, nil
+		return strings.ToLower(pipeline), nil
 	}
 
 	if pipelineSel != nil {

libbeat/outputs/elasticsearch/client_proxy_test.go

@@ -190,7 +190,7 @@ func doClientPing(t *testing.T) {
 			Headers:      map[string]string{headerTestField: headerTestValue},
 			ProxyDisable: proxyDisable != "",
 		},
-		Index: outil.MakeSelector(outil.ConstSelectorExpr("test")),
+		Index: outil.MakeSelector(outil.ConstSelectorExpr("test", outil.SelectorLowerCase)),
 	}
 	if proxy != "" {
 		proxyURL, err := url.Parse(proxy)

libbeat/outputs/elasticsearch/client_test.go

@@ -228,7 +228,7 @@ func TestClientWithHeaders(t *testing.T) {
 				"X-Test": "testing value",
 			},
 		},
-		Index: outil.MakeSelector(outil.ConstSelectorExpr("test")),
+		Index: outil.MakeSelector(outil.ConstSelectorExpr("test", outil.SelectorLowerCase)),
 	}, nil)
 	assert.NoError(t, err)
 

libbeat/outputs/elasticsearch/elasticsearch.go

@@ -133,12 +133,7 @@ func buildSelectors(
 		return index, pipeline, err
 	}
 
-	pipelineSel, err := outil.BuildSelectorFromConfig(cfg, outil.Settings{
-		Key:              "pipeline",
-		MultiKey:         "pipelines",
-		EnableSingleOnly: true,
-		FailEmpty:        false,
-	})
+	pipelineSel, err := buildPipelineSelector(cfg)
 	if err != nil {
 		return index, pipeline, err
 	}
@@ -149,3 +144,13 @@ func buildSelectors(
 
 	return index, pipeline, err
 }
+
+func buildPipelineSelector(cfg *common.Config) (outil.Selector, error) {
+	return outil.BuildSelectorFromConfig(cfg, outil.Settings{
+		Key:              "pipeline",
+		MultiKey:         "pipelines",
+		EnableSingleOnly: true,
+		FailEmpty:        false,
+		Case:             outil.SelectorLowerCase,
+	})
+}

libbeat/outputs/elasticsearch/elasticsearch_test.go

@@ -21,6 +21,8 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/elastic/beats/v7/libbeat/beat"
+	"github.com/elastic/beats/v7/libbeat/common"
 	"github.com/elastic/beats/v7/libbeat/esleg/eslegclient"
 )
 
@@ -73,3 +75,59 @@ func TestGlobalConnectCallbacksManagement(t *testing.T) {
 		t.Fatalf("third callback cannot be retrieved")
 	}
 }
+
+func TestPipelineSelection(t *testing.T) {
+	cases := map[string]struct {
+		cfg   map[string]interface{}
+		event beat.Event
+		want  string
+	}{
+		"no pipline configured": {},
+		"pipeline configured": {
+			cfg:  map[string]interface{}{"pipeline": "test"},
+			want: "test",
+		},
+		"pipeline must be lowercase": {
+			cfg:  map[string]interface{}{"pipeline": "Test"},
+			want: "test",
+		},
+		"pipeline via event meta": {
+			event: beat.Event{Meta: common.MapStr{"pipeline": "test"}},
+			want:  "test",
+		},
+		"pipeline via event meta must be lowercase": {
+			event: beat.Event{Meta: common.MapStr{"pipeline": "Test"}},
+			want:  "test",
+		},
+		"pipelines setting": {
+			cfg: map[string]interface{}{
+				"pipelines": []map[string]interface{}{{"pipeline": "test"}},
+			},
+			want: "test",
+		},
+		"pipelines setting must be lowercase": {
+			cfg: map[string]interface{}{
+				"pipelines": []map[string]interface{}{{"pipeline": "Test"}},
+			},
+			want: "test",
+		},
+	}
+
+	for name, test := range cases {
+		t.Run(name, func(t *testing.T) {
+			selector, err := buildPipelineSelector(common.MustNewConfigFrom(test.cfg))
+			if err != nil {
+				t.Fatalf("Failed to parse configuration: %v", err)
+			}
+
+			got, err := getPipeline(&test.event, &selector)
+			if err != nil {
+				t.Fatalf("Failed to create pipeline name: %v", err)
+			}
+
+			if test.want != got {
+				t.Errorf("Pipeline name missmatch (want: %v, got: %v)", test.want, got)
+			}
+		})
+	}
+}

libbeat/outputs/kafka/config_test.go

@@ -23,6 +23,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/elastic/beats/v7/libbeat/beat"
 	"github.com/elastic/beats/v7/libbeat/common"
 	"github.com/elastic/beats/v7/libbeat/internal/testutil"
 	"github.com/elastic/beats/v7/libbeat/logp"
@@ -131,3 +132,64 @@ func TestBackoffFunc(t *testing.T) {
 		})
 	}
 }
+
+func TestTopicSelection(t *testing.T) {
+	cases := map[string]struct {
+		cfg   map[string]interface{}
+		event beat.Event
+		want  string
+	}{
+		"topic configured": {
+			cfg:  map[string]interface{}{"topic": "test"},
+			want: "test",
+		},
+		"topic must keep case": {
+			cfg:  map[string]interface{}{"topic": "Test"},
+			want: "Test",
+		},
+		"topics setting": {
+			cfg: map[string]interface{}{
+				"topics": []map[string]interface{}{{"topic": "test"}},
+			},
+			want: "test",
+		},
+		"topics setting must keep case": {
+			cfg: map[string]interface{}{
+				"topics": []map[string]interface{}{{"topic": "Test"}},
+			},
+			want: "Test",
+		},
+		"use event field": {
+			cfg: map[string]interface{}{"topic": "test-%{[field]}"},
+			event: beat.Event{
+				Fields: common.MapStr{"field": "from-event"},
+			},
+			want: "test-from-event",
+		},
+		"use event field must keep case": {
+			cfg: map[string]interface{}{"topic": "Test-%{[field]}"},
+			event: beat.Event{
+				Fields: common.MapStr{"field": "From-Event"},
+			},
+			want: "Test-From-Event",
+		},
+	}
+
+	for name, test := range cases {
+		t.Run(name, func(t *testing.T) {
+			selector, err := buildTopicSelector(common.MustNewConfigFrom(test.cfg))
+			if err != nil {
+				t.Fatalf("Failed to parse configuration: %v", err)
+			}
+
+			got, err := selector.Select(&test.event)
+			if err != nil {
+				t.Fatalf("Failed to create topic name: %v", err)
+			}
+
+			if test.want != got {
+				t.Errorf("Pipeline name missmatch (want: %v, got: %v)", test.want, got)
+			}
+		})
+	}
+}

libbeat/outputs/kafka/kafka.go

@@ -66,12 +66,7 @@ func makeKafka(
 		return outputs.Fail(err)
 	}
 
-	topic, err := outil.BuildSelectorFromConfig(cfg, outil.Settings{
-		Key:              "topic",
-		MultiKey:         "topics",
-		EnableSingleOnly: true,
-		FailEmpty:        true,
-	})
+	topic, err := buildTopicSelector(cfg)
 	if err != nil {
 		return outputs.Fail(err)
 	}
@@ -102,3 +97,13 @@ func makeKafka(
 	}
 	return outputs.Success(config.BulkMaxSize, retry, client)
 }
+
+func buildTopicSelector(cfg *common.Config) (outil.Selector, error) {
+	return outil.BuildSelectorFromConfig(cfg, outil.Settings{
+		Key:              "topic",
+		MultiKey:         "topics",
+		EnableSingleOnly: true,
+		FailEmpty:        true,
+		Case:             outil.SelectorKeepCase,
+	})
+}

libbeat/outputs/logstash/logstash_integration_test.go

@@ -94,7 +94,7 @@ func esConnect(t *testing.T, index string) *esConnection {
 
 	host := getElasticsearchHost()
 	indexFmt := fmtstr.MustCompileEvent(fmt.Sprintf("%s-%%{+yyyy.MM.dd}", index))
-	indexFmtExpr, _ := outil.FmtSelectorExpr(indexFmt, "")
+	indexFmtExpr, _ := outil.FmtSelectorExpr(indexFmt, "", outil.SelectorLowerCase)
 	indexSel := outil.MakeSelector(indexFmtExpr)
 	index, _ = indexSel.Select(&beat.Event{
 		Timestamp: ts,