Fix drop_fields when the first field is unknown

CHANGELOG.asciidoc

@@ -29,6 +29,8 @@ https://github.com/elastic/beats/compare/v5.0.0-beta1...master[Check the HEAD di
 
 *Affecting all Beats*
 
+- Fix ignoring all fields from drop_fields in case the first field is unknown. {pull}2685[2685]
+
 *Metricbeat*
 
 - Fix default configuration file on Windows to not enabled the `load` metricset. {pull}2632[2632]

libbeat/common/mapstr.go

@@ -63,6 +63,7 @@ func (m MapStr) Delete(key string) error {
 	keysLen := len(keyParts)
 
 	mapp := m
+
 	for i := 0; i < keysLen-1; i++ {
 		keyPart := keyParts[i]
 
@@ -75,8 +76,11 @@ func (m MapStr) Delete(key string) error {
 			return fmt.Errorf("unknown key %s", keyPart)
 		}
 	}
-	delete(mapp, keyParts[keysLen-1])
-	return nil
+	if _, ok := mapp[keyParts[keysLen-1]]; ok {
+		delete(mapp, keyParts[keysLen-1])
+		return nil
+	}
+	return fmt.Errorf("unknown key %s", keyParts[keysLen-1])
 }
 
 func (m MapStr) CopyFieldsTo(to MapStr, key string) error {

libbeat/processors/actions/drop_fields.go

@@ -42,14 +42,16 @@ func newDropFields(c common.Config) (processors.Processor, error) {
 }
 
 func (f dropFields) Run(event common.MapStr) (common.MapStr, error) {
+	errors := []string{}
+
 	for _, field := range f.Fields {
 		err := event.Delete(field)
 		if err != nil {
-			return event, fmt.Errorf("Fail to delete key %s: %s", field, err)
+			errors = append(errors, err.Error())
 		}
 
 	}
-	return event, nil
+	return event, fmt.Errorf(strings.Join(errors, ", "))
 }
 
 func (f dropFields) String() string {

libbeat/processors/actions/include_fields.go

@@ -47,22 +47,23 @@ func newIncludeFields(c common.Config) (processors.Processor, error) {
 
 func (f includeFields) Run(event common.MapStr) (common.MapStr, error) {
 	filtered := common.MapStr{}
+	errors := []string{}
 
 	for _, field := range f.Fields {
 		hasKey, err := event.HasKey(field)
 		if err != nil {
-			return filtered, fmt.Errorf("Fail to check the key %s: %s", field, err)
+			errors = append(errors, err.Error())
 		}
 
 		if hasKey {
 			errorOnCopy := event.CopyFieldsTo(filtered, field)
 			if errorOnCopy != nil {
-				return filtered, fmt.Errorf("Fail to copy key %s: %s", field, err)
+				errors = append(errors, err.Error())
 			}
 		}
 	}
 
-	return filtered, nil
+	return filtered, fmt.Errorf(strings.Join(errors, ", "))
 }
 
 func (f includeFields) String() string {

libbeat/processors/processor_test.go

@@ -569,3 +569,54 @@ func TestBadConditionConfig(t *testing.T) {
 	assert.NotNil(t, err)
 
 }
+
+func TestDropMissingFields(t *testing.T) {
+
+	yml := []map[string]interface{}{
+		map[string]interface{}{
+			"drop_fields": map[string]interface{}{
+				"fields": []string{"foo.bar", "proc.cpu", "proc.sss", "beat", "mem"},
+			},
+		},
+	}
+
+	processors := GetProcessors(t, yml)
+
+	event := common.MapStr{
+		"@timestamp": "2016-01-24T18:35:19.308Z",
+		"beat": common.MapStr{
+			"hostname": "mar",
+			"name":     "my-shipper-1",
+		},
+
+		"proc": common.MapStr{
+			"cpu": common.MapStr{
+				"start_time": "Jan14",
+				"system":     26027,
+				"total":      79390,
+				"total_p":    0,
+				"user":       53363,
+			},
+			"cmdline": "/sbin/launchd",
+		},
+		"mem": common.MapStr{
+			"rss":   11194368,
+			"rss_p": 0,
+			"share": 0,
+			"size":  2555572224,
+		},
+		"type": "process",
+	}
+
+	processedEvent := processors.Run(event)
+
+	expectedEvent := common.MapStr{
+		"@timestamp": "2016-01-24T18:35:19.308Z",
+		"proc": common.MapStr{
+			"cmdline": "/sbin/launchd",
+		},
+		"type": "process",
+	}
+
+	assert.Equal(t, expectedEvent, processedEvent)
+}