Add validate command to validate collector config

.chloggen/add-dry-run-flag-validate-all-fields.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: service
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note:  Added dry run flag to validate config file without running collector.
+
+# One or more tracking issues or pull requests related to the change
+issues: [4671]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

otelcol/collector.go

@@ -192,6 +192,15 @@ func (col *Collector) reloadConfiguration(ctx context.Context) error {
 	return nil
 }
 
+func (col *Collector) DryRun(ctx context.Context) error {
+	cfg, err := col.set.ConfigProvider.Get(ctx, col.set.Factories)
+	if err != nil {
+		return fmt.Errorf("failed to get config: %w", err)
+	}
+
+	return cfg.Validate()
+}
+
 // Run starts the collector according to the given configuration, and waits for it to complete.
 // Consecutive calls to Run are not allowed, Run shouldn't be called once a collector is shut down.
 func (col *Collector) Run(ctx context.Context) error {

otelcol/collector_test.go

@@ -350,6 +350,25 @@ func TestCollectorClosedStateOnStartUpError(t *testing.T) {
 	assert.Equal(t, StateClosed, col.GetState())
 }
 
+func TestCollectorDryRun(t *testing.T) {
+	factories, err := nopFactories()
+	require.NoError(t, err)
+
+	cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-invalid.yaml")}))
+	require.NoError(t, err)
+
+	// Load a bad config causing startup to fail
+	set := CollectorSettings{
+		BuildInfo:      component.NewDefaultBuildInfo(),
+		Factories:      factories,
+		ConfigProvider: cfgProvider,
+	}
+	col, err := NewCollector(set)
+	require.NoError(t, err)
+
+	require.Error(t, col.DryRun(context.Background()))
+}
+
 func startCollector(ctx context.Context, t *testing.T, col *Collector) *sync.WaitGroup {
 	wg := &sync.WaitGroup{}
 	wg.Add(1)

otelcol/command.go

@@ -28,6 +28,7 @@ func NewCommand(set CollectorSettings) *cobra.Command {
 		},
 	}
 	rootCmd.AddCommand(newBuildSubCommand(set))
+	rootCmd.AddCommand(newValidateSubCommand(set, flagSet))
 	rootCmd.Flags().AddGoFlagSet(flagSet)
 	return rootCmd
 }

otelcol/command_validate.go

@@ -0,0 +1,42 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package otelcol // import "go.opentelemetry.io/collector/otelcol"
+
+import (
+	"errors"
+	"flag"
+
+	"github.com/spf13/cobra"
+)
+
+// newValidateSubCommand constructs a new validate sub command using the given CollectorSettings.
+func newValidateSubCommand(set CollectorSettings, flagSet *flag.FlagSet) *cobra.Command {
+	validateCmd := &cobra.Command{
+		Use:   "validate",
+		Short: "Validates the config without running the collector",
+		Args:  cobra.ExactArgs(0),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if set.ConfigProvider == nil {
+				var err error
+
+				configFlags := getConfigFlag(flagSet)
+				if len(configFlags) == 0 {
+					return errors.New("at least one config flag must be provided")
+				}
+
+				set.ConfigProvider, err = NewConfigProvider(newDefaultConfigProviderSettings(configFlags))
+				if err != nil {
+					return err
+				}
+			}
+			col, err := NewCollector(set)
+			if err != nil {
+				return err
+			}
+			return col.DryRun(cmd.Context())
+		},
+	}
+	validateCmd.Flags().AddGoFlagSet(flagSet)
+	return validateCmd
+}

otelcol/command_validate_test.go

@@ -0,0 +1,46 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package otelcol
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/collector/confmap"
+	"go.opentelemetry.io/collector/confmap/converter/expandconverter"
+	"go.opentelemetry.io/collector/confmap/provider/fileprovider"
+	"go.opentelemetry.io/collector/featuregate"
+)
+
+func TestValidateSubCommandNoConfig(t *testing.T) {
+	factories, err := nopFactories()
+	require.NoError(t, err)
+
+	cmd := newValidateSubCommand(CollectorSettings{Factories: factories}, flags(featuregate.GlobalRegistry()))
+	err = cmd.Execute()
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "at least one config flag must be provided")
+}
+
+func TestValidateSubCommandInvalidComponents(t *testing.T) {
+	factories, err := nopFactories()
+	require.NoError(t, err)
+
+	cfgProvider, err := NewConfigProvider(
+		ConfigProviderSettings{
+			ResolverSettings: confmap.ResolverSettings{
+				URIs:       []string{filepath.Join("testdata", "otelcol-invalid-components.yaml")},
+				Providers:  map[string]confmap.Provider{"file": fileprovider.New()},
+				Converters: []confmap.Converter{expandconverter.New()},
+			},
+		})
+	require.NoError(t, err)
+
+	cmd := newValidateSubCommand(CollectorSettings{Factories: factories, ConfigProvider: cfgProvider}, flags(featuregate.GlobalRegistry()))
+	err = cmd.Execute()
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "unknown type: \"nosuchprocessor\"")
+}

otelcol/testdata/otelcol-invalid-components.yaml

@@ -0,0 +1,12 @@
+receivers:
+  nop:
+exporters:
+  nop:
+processors:
+  nosuchprocessor:
+service:
+  pipelines:
+    traces:
+      receivers: [nop]
+      exporters: [nop]
+      processors: [nop]

service/README.md

@@ -143,5 +143,10 @@ exporters:
 extensions:
    - zpages
    - memory_ballast
+```
+
+## How to validate configuration file and return all errors without running collector
 
-```
+```bash
+   ./otelcorecol validate --config=file:examples/local/otel-config.yaml
+```