feat: add 'config validate' command to diagnose config issues without other checks (#232)

### Description

Add 'config validate' command to diagnose config issues without other
checks. This can be used by our helm chart to check all of the config
maps.

Examples:
```sh
$ ./observe-agent config validate 
❌ invalid config
Error: service::pipelines::metrics/agent-filestats: references exporter "otlphttp/observemetrics2" which is not configured

# after fixing my config
$ ./observe-agent config validate 
✅ configuration is valid
```

This also adds a hidden `config-mode` flag so you can (e.g.) validate
the bundled docker config from a mac build:
```sh
$ ./observe-agent config --render-otel | grep eventlog

$ ./observe-agent --config-mode windows config --render-otel | grep eventlog
    windowseventlog/host_monitoring-application:
    windowseventlog/host_monitoring-security:
    windowseventlog/host_monitoring-system:
                - windowseventlog/host_monitoring-application
                - windowseventlog/host_monitoring-security
                - windowseventlog/host_monitoring-system
```

Author: obs-gh-mattcotter

internal/commands/config/config.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/observeinc/observe-agent/internal/commands/util/logger"
 	"github.com/observeinc/observe-agent/internal/root"
+	"github.com/observeinc/observe-agent/observecol"
 	"github.com/spf13/cobra"
 )
 
@@ -41,7 +42,32 @@ bundled OTel configuration.`,
 	},
 }
 
+var configValidateCmd = &cobra.Command{
+	Use:          "validate",
+	Short:        "Validates the configuration for this agent.",
+	SilenceUsage: true,
+	RunE: func(cmd *cobra.Command, args []string) error {
+		ctx := logger.WithCtx(context.Background(), logger.GetNop())
+		col, cleanup, err := observecol.GetOtelCollector(ctx)
+		if cleanup != nil {
+			defer cleanup()
+		}
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "❌ failed to generate config")
+			return err
+		}
+		err = col.DryRun(ctx)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "❌ invalid config")
+			return err
+		}
+		fmt.Fprintln(os.Stderr, "✅ configuration is valid")
+		return nil
+	},
+}
+
 func init() {
+	configCmd.AddCommand(configValidateCmd)
 	configCmd.Flags().Bool("render-otel-details", false, "Print the full resolved otel configuration including default values after the otel components perform their semantic processing.")
 	configCmd.Flags().Bool("render-otel", false, "Print a single rendered otel configuration file. This file is equivalent to the bundled configuration enabled in the observe-agent config.")
 	root.RootCmd.AddCommand(configCmd)

internal/commands/config/config_test.go

@@ -109,7 +109,7 @@ func runSnapshotTest(t *testing.T, test snapshotTest) {
 	assert.True(t, ok)
 	curPath := path.Dir(filename)
 
-	// Set the template base dir for all connections
+	// Set the template overrides for all connections
 	for _, conn := range connections.AllConnectionTypes {
 		conn.ApplyOptions(connections.WithConfigTemplateOverrides(getTemplateOverrides(t, test.packageType, curPath)))
 	}

internal/connections/bundledconfig/bundledconfig.go

@@ -9,8 +9,10 @@ import (
 	"github.com/observeinc/observe-agent/internal/connections/bundledconfig/windows"
 )
 
+type ConfigTemplates = map[string]embed.FS
+
 // TODO break up some of the larger connections in order to share more configs.
-var SharedTemplateFS = map[string]embed.FS{
+var SharedTemplateFS = ConfigTemplates{
 	"common/attributes.yaml.tmpl":                shared.AttributesTemplateFS,
 	"common/internal_telemetry.yaml.tmpl":        shared.InternalTelemetryTemplateFS,
 	"common/health_check.yaml.tmpl":              shared.HealthCheckTemplateFS,
@@ -23,23 +25,23 @@ var SharedTemplateFS = map[string]embed.FS{
 	"self_monitoring/logs_and_metrics.yaml.tmpl": shared.LogsAndMetricsTemplateFS,
 }
 
-var DockerTemplateFS = map[string]embed.FS{
+var DockerTemplateFS = ConfigTemplates{
 	"common/base.yaml.tmpl":                      docker.BaseTemplateFS,
 	"host_monitoring/logs.yaml.tmpl":             docker.LogsTemplateFS,
 	"host_monitoring/host_metrics.yaml.tmpl":     docker.HostMetricsTemplateFS,
 	"host_monitoring/process_metrics.yaml.tmpl":  docker.ProcessMetricsTemplateFS,
 	"self_monitoring/logs_and_metrics.yaml.tmpl": docker.LogsAndMetricsTemplateFS,
 }
 
-var LinuxTemplateFS = map[string]embed.FS{
+var LinuxTemplateFS = ConfigTemplates{
 	"host_monitoring/logs.yaml.tmpl":             linux.LogsTemplateFS,
 	"host_monitoring/host_metrics.yaml.tmpl":     linux.HostMetricsTemplateFS,
 	"self_monitoring/logs_and_metrics.yaml.tmpl": linux.LogsAndMetricsTemplateFS,
 }
 
-var MacOSTemplateFS = map[string]embed.FS{}
+var MacOSTemplateFS = ConfigTemplates{}
 
-var WindowsTemplateFS = map[string]embed.FS{
+var WindowsTemplateFS = ConfigTemplates{
 	"common/base.yaml.tmpl":                  windows.BaseTemplateFS,
 	"host_monitoring/logs.yaml.tmpl":         windows.LogsTemplateFS,
 	"host_monitoring/host_metrics.yaml.tmpl": windows.HostMetricsTemplateFS,

internal/connections/connections.go

@@ -24,14 +24,12 @@ type BundledConfigFragment struct {
 	colConfigFilePath string
 }
 
-type ConfigOverrides = map[string]embed.FS
-
 type ConnectionType struct {
 	Name                   string
 	BundledConfigFragments []BundledConfigFragment
 	EnabledCheck           EnabledCheckFn
 
-	templateOverrides ConfigOverrides
+	templateOverrides bundledconfig.ConfigTemplates
 }
 
 func (c *ConnectionType) getTemplate(tplName string) (*template.Template, error) {
@@ -111,7 +109,7 @@ func MakeConnectionType(name string, enabledCheck EnabledCheckFn, fragments []Bu
 	return c
 }
 
-func WithConfigTemplateOverrides(templateOverrides ConfigOverrides) ConnectionTypeOption {
+func WithConfigTemplateOverrides(templateOverrides bundledconfig.ConfigTemplates) ConnectionTypeOption {
 	return func(c *ConnectionType) {
 		c.templateOverrides = templateOverrides
 	}

internal/root/root.go

@@ -15,12 +15,14 @@ import (
 	"github.com/observeinc/observe-agent/internal/commands/util/logger"
 	"github.com/observeinc/observe-agent/internal/config"
 	"github.com/observeinc/observe-agent/internal/connections"
+	"github.com/observeinc/observe-agent/internal/connections/bundledconfig"
 	"github.com/observeinc/observe-agent/observecol"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 )
 
 var CfgFile string
+var configMode string
 
 // RootCmd represents the base command when called without any subcommands
 var RootCmd = &cobra.Command{
@@ -45,12 +47,39 @@ func init() {
 
 	flags := RootCmd.PersistentFlags()
 	flags.StringVar(&CfgFile, "observe-config", "", "observe-agent config file path")
+	flags.StringVar(&configMode, "config-mode", "", "The mode to use for bundled config. Valid values are Linux, Docker, Mac, and Windows.")
+	flags.MarkHidden("config-mode")
 	observecol.AddConfigFlags(flags)
 	observecol.AddFeatureGateFlag(flags)
 }
 
+func setConfigMode() {
+	var overrides bundledconfig.ConfigTemplates
+	switch strings.ToLower(configMode) {
+	case "":
+		return
+	case "linux":
+		overrides = bundledconfig.LinuxTemplateFS
+	case "docker":
+		overrides = bundledconfig.DockerTemplateFS
+	case "mac":
+		overrides = bundledconfig.MacOSTemplateFS
+	case "windows":
+		overrides = bundledconfig.WindowsTemplateFS
+	default:
+		fmt.Fprintf(os.Stderr, "Invalid config mode specified: %s. Valid values are Linux, Docker, Mac, and Windows.\n", configMode)
+		os.Exit(1)
+	}
+	// Set the template overrides for all connections
+	for _, conn := range connections.AllConnectionTypes {
+		conn.ApplyOptions(connections.WithConfigTemplateOverrides(overrides))
+	}
+
+}
+
 // InitConfig reads in config file and ENV variables if set.
 func InitConfig() {
+	setConfigMode()
 	ctx := logger.WithCtx(context.Background(), logger.Get())
 	// Some keys in OTEL component configs use "." as part of the key but viper ends up parsing that into
 	// a subobject since the default key delimiter is "." which causes config validation to fail.