Add option to support moved filebeat modules

CHANGELOG.asciidoc

@@ -82,6 +82,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha1...master[Check the HEAD d
 - Added `detect_null_bytes` selector to detect null bytes from a io.reader. {pull}9210[9210]
 - Added `syslog_host` variable to HAProxy module to allow syslog listener to bind to configured host. {pull}9366[9366]
 - Added support on Traefik for Common Log Format and Combined Log Format mixed which is the default Traefik format {issue}8015[8015] {issue}6111[6111] {pull}8768[8768].
+- Add option to modules.yml file to indicate that a module has been moved {pull}9432[9432].
 
 *Heartbeat*
 

filebeat/fileset/modules.go

@@ -26,6 +26,7 @@ import (
 	"strings"
 
 	"github.com/pkg/errors"
+	yaml "gopkg.in/yaml.v2"
 
 	"github.com/elastic/beats/libbeat/common"
 	"github.com/elastic/beats/libbeat/kibana"
@@ -57,6 +58,12 @@ func newModuleRegistry(modulesPath string,
 			continue
 		}
 
+		// Look for moved modules
+		if module, moved := getCurrentModuleName(modulesPath, mcfg.Module); moved {
+			logp.Warn("Using old name '%s' for module '%s', please update your configuration", mcfg.Module, module)
+			mcfg.Module = module
+		}
+
 		reg.registry[mcfg.Module] = map[string]*Fileset{}
 		moduleFilesets, err := getModuleFilesets(modulesPath, mcfg.Module)
 		if err != nil {
@@ -180,7 +187,26 @@ func mcfgFromConfig(cfg *common.Config) (*ModuleConfig, error) {
 	return &mcfg, nil
 }
 
+func getCurrentModuleName(modulePath, module string) (string, bool) {
+	moduleConfigPath := filepath.Join(modulePath, module, "module.yml")
+	d, err := ioutil.ReadFile(moduleConfigPath)
+	if err != nil {
+		return module, false
+	}
+
+	var moduleConfig struct {
+		MovedTo string `yaml:"movedTo"`
+	}
+	err = yaml.Unmarshal(d, &moduleConfig)
+	if err == nil && moduleConfig.MovedTo != "" {
+		return moduleConfig.MovedTo, true
+	}
+
+	return module, false
+}
+
 func getModuleFilesets(modulePath, module string) ([]string, error) {
+	module, _ = getCurrentModuleName(modulePath, module)
 	fileInfos, err := ioutil.ReadDir(filepath.Join(modulePath, module))
 	if err != nil {
 		return []string{}, err

filebeat/fileset/modules_test.go

@@ -126,6 +126,24 @@ func TestNewModuleRegistryConfig(t *testing.T) {
 	assert.NotContains(t, reg.registry["nginx"], "error")
 }
 
+func TestMovedModule(t *testing.T) {
+	modulesPath, err := filepath.Abs("./test/moved_module")
+	assert.NoError(t, err)
+
+	configs := []*ModuleConfig{
+		&ModuleConfig{
+			Module: "old",
+			Filesets: map[string]*FilesetConfig{
+				"test": {},
+			},
+		},
+	}
+
+	reg, err := newModuleRegistry(modulesPath, configs, nil, "5.2.0")
+	assert.NoError(t, err)
+	assert.NotNil(t, reg)
+}
+
 func TestApplyOverrides(t *testing.T) {
 	falseVar := false
 	trueVar := true

filebeat/fileset/test/moved_module/old/module.yml

@@ -0,0 +1 @@
+movedTo: new