[v2] Fix inspect command (#805)

* Write the inspect command for v2.

* Fix lint.

* Fix code review. Load inputs from inputs.d for inspect.

* Fix lint.

* Refactor to use errgroup.

* Remove unused struct.

internal/pkg/agent/application/application.go

@@ -6,7 +6,6 @@ package application
 
 import (
 	"fmt"
-	"path/filepath"
 
 	"go.elastic.co/apm"
 
@@ -20,17 +19,11 @@ import (
 	"github.com/elastic/elastic-agent/internal/pkg/capabilities"
 	"github.com/elastic/elastic-agent/internal/pkg/composable"
 	"github.com/elastic/elastic-agent/internal/pkg/config"
-	"github.com/elastic/elastic-agent/internal/pkg/dir"
 	"github.com/elastic/elastic-agent/pkg/component"
 	"github.com/elastic/elastic-agent/pkg/component/runtime"
 	"github.com/elastic/elastic-agent/pkg/core/logger"
 )
 
-type discoverFunc func() ([]string, error)
-
-// ErrNoConfiguration is returned when no configuration are found.
-var ErrNoConfiguration = errors.New("no configuration found", errors.TypeConfig)
-
 // New creates a new Agent and bootstrap the required subsystem.
 func New(
 	log *logger.Logger,
@@ -83,8 +76,8 @@ func New(
 	if configuration.IsStandalone(cfg.Fleet) {
 		log.Info("Parsed configuration and determined agent is managed locally")
 
-		loader := config.NewLoader(log, externalConfigsGlob())
-		discover := discoverer(pathConfigFile, cfg.Settings.Path, externalConfigsGlob())
+		loader := config.NewLoader(log, paths.ExternalInputs())
+		discover := config.Discoverer(pathConfigFile, cfg.Settings.Path, paths.ExternalInputs())
 		if !cfg.Settings.Reload.Enabled {
 			log.Debug("Reloading of configuration is off")
 			configMgr = newOnce(log, discover, loader)
@@ -173,28 +166,3 @@ func mergeFleetConfig(rawConfig *config.Config) (storage.Store, *configuration.C
 
 	return store, cfg, nil
 }
-
-func externalConfigsGlob() string {
-	return filepath.Join(paths.Config(), configuration.ExternalInputsPattern)
-}
-
-func discoverer(patterns ...string) discoverFunc {
-	p := make([]string, 0, len(patterns))
-	for _, newP := range patterns {
-		if len(newP) == 0 {
-			continue
-		}
-
-		p = append(p, newP)
-	}
-
-	if len(p) == 0 {
-		return func() ([]string, error) {
-			return []string{}, ErrNoConfiguration
-		}
-	}
-
-	return func() ([]string, error) {
-		return dir.DiscoverFiles(p...)
-	}
-}

internal/pkg/agent/application/once.go

@@ -17,13 +17,13 @@ import (
 
 type once struct {
 	log      *logger.Logger
-	discover discoverFunc
+	discover config.DiscoverFunc
 	loader   *config.Loader
 	ch       chan coordinator.ConfigChange
 	errCh    chan error
 }
 
-func newOnce(log *logger.Logger, discover discoverFunc, loader *config.Loader) *once {
+func newOnce(log *logger.Logger, discover config.DiscoverFunc, loader *config.Loader) *once {
 	return &once{log: log, discover: discover, loader: loader, ch: make(chan coordinator.ConfigChange), errCh: make(chan error)}
 }
 
@@ -34,7 +34,7 @@ func (o *once) Run(ctx context.Context) error {
 	}
 
 	if len(files) == 0 {
-		return ErrNoConfiguration
+		return config.ErrNoConfiguration
 	}
 
 	cfg, err := readfiles(files, o.loader)

internal/pkg/agent/application/paths/common.go

@@ -23,6 +23,9 @@ const (
 	tempSubdir        = "tmp"
 )
 
+// ExternalInputsPattern is a glob that matches the paths of external configuration files.
+var ExternalInputsPattern = filepath.Join("inputs.d", "*.yml")
+
 var (
 	topPath         string
 	configPath      string
@@ -69,7 +72,7 @@ func TempDir() string {
 	tmpDir := filepath.Join(Data(), tempSubdir)
 	tmpCreator.Do(func() {
 		// create tempdir as it probably don't exists
-		os.MkdirAll(tmpDir, 0750)
+		_ = os.MkdirAll(tmpDir, 0750)
 	})
 	return tmpDir
 }
@@ -119,6 +122,11 @@ func ConfigFile() string {
 	return filepath.Join(Config(), configFilePath)
 }
 
+// ExternalInputs returns the path to load external inputs from.
+func ExternalInputs() string {
+	return filepath.Join(Config(), ExternalInputsPattern)
+}
+
 // Data returns the data directory for Agent
 func Data() string {
 	if unversionedHome {

internal/pkg/agent/application/periodic.go

@@ -22,7 +22,7 @@ type periodic struct {
 	period   time.Duration
 	watcher  *filewatcher.Watch
 	loader   *config.Loader
-	discover discoverFunc
+	discover config.DiscoverFunc
 	ch       chan coordinator.ConfigChange
 	errCh    chan error
 }
@@ -62,7 +62,7 @@ func (p *periodic) work() error {
 	}
 
 	if len(files) == 0 {
-		return ErrNoConfiguration
+		return config.ErrNoConfiguration
 	}
 
 	// Reset the state of the watched files
@@ -115,7 +115,7 @@ func (p *periodic) work() error {
 func newPeriodic(
 	log *logger.Logger,
 	period time.Duration,
-	discover discoverFunc,
+	discover config.DiscoverFunc,
 	loader *config.Loader,
 ) *periodic {
 	w, err := filewatcher.New(log, filewatcher.DefaultComparer)

internal/pkg/agent/cmd/diagnostics.go

@@ -398,14 +398,19 @@ func outputDiagnostics(w io.Writer, d DiagnosticsInfo) error {
 }
 
 func gatherConfig() (AgentConfig, error) {
+	log, err := newErrorLogger()
+	if err != nil {
+		return AgentConfig{}, err
+	}
+
 	cfg := AgentConfig{}
 	localCFG, err := loadConfig(nil)
 	if err != nil {
 		return cfg, err
 	}
 	cfg.ConfigLocal = localCFG
 
-	renderedCFG, err := operations.LoadFullAgentConfig(paths.ConfigFile(), true)
+	renderedCFG, err := operations.LoadFullAgentConfig(log, paths.ConfigFile(), true)
 	if err != nil {
 		return cfg, err
 	}
@@ -434,11 +439,6 @@ func gatherConfig() (AgentConfig, error) {
 			return AgentConfig{}, err
 		}
 
-		log, err := newErrorLogger()
-		if err != nil {
-			return AgentConfig{}, err
-		}
-
 		// Get process config - uses same approach as inspect output command.
 		// Does not contact server process to request configs.
 		pMap, err := getProgramsFromConfig(log, agentInfo, renderedCFG, isStandalone)