auth.go

// Package auth provides utilities to create a Flow component from
// OpenTelemetry Collector authentication extensions.
//
// Other OpenTelemetry Collector extensions are better served as generic Flow
// components rather than being placed in the otelcol namespace.
package auth

import (
	"context"
	"os"

	"github.com/grafana/agent/component"
	"github.com/grafana/agent/component/otelcol/internal/lazycollector"
	"github.com/grafana/agent/component/otelcol/internal/scheduler"
	"github.com/grafana/agent/pkg/build"
	"github.com/grafana/agent/pkg/util/zapadapter"
	"github.com/grafana/river"
	"github.com/prometheus/client_golang/prometheus"
	otelcomponent "go.opentelemetry.io/collector/component"
	otelextension "go.opentelemetry.io/collector/extension"
	sdkprometheus "go.opentelemetry.io/otel/exporters/prometheus"
	"go.opentelemetry.io/otel/sdk/metric"
)

// Arguments is an extension of component.Arguments which contains necessary
// settings for OpenTelemetry Collector authentication extensions.
type Arguments interface {
	component.Arguments

	// Convert converts the Arguments into an OpenTelemetry Collector
	// authentication extension configuration.
	Convert() (otelcomponent.Config, error)

	// Extensions returns the set of extensions that the configured component is
	// allowed to use.
	Extensions() map[otelcomponent.ID]otelextension.Extension

	// Exporters returns the set of exporters that are exposed to the configured
	// component.
	Exporters() map[otelcomponent.DataType]map[otelcomponent.ID]otelcomponent.Component
}

// Exports is a common Exports type for Flow components which expose
// OpenTelemetry Collector authentication extensions.
type Exports struct {
	// Handler is the managed component. Handler is updated any time the
	// extension is updated.
	Handler Handler `river:"handler,attr"`
}

// Handler combines an extension with its ID.
type Handler struct {
	ID        otelcomponent.ID
	Extension otelextension.Extension
}

var _ river.Capsule = Handler{}

// RiverCapsule marks Handler as a capsule type.
func (Handler) RiverCapsule() {}

// Auth is a Flow component shim which manages an OpenTelemetry Collector
// authentication extension.
type Auth struct {
	ctx    context.Context
	cancel context.CancelFunc

	opts    component.Options
	factory otelextension.Factory

	sched     *scheduler.Scheduler
	collector *lazycollector.Collector
}

var (
	_ component.Component       = (*Auth)(nil)
	_ component.HealthComponent = (*Auth)(nil)
)

// New creates a new Flow component which encapsulates an OpenTelemetry
// Collector authentication extension. args must hold a value of the argument
// type registered with the Flow component.
//
// The registered component must be registered to export the Exports type from
// this package, otherwise New will panic.
func New(opts component.Options, f otelextension.Factory, args Arguments) (*Auth, error) {
	ctx, cancel := context.WithCancel(context.Background())

	// Create a lazy collector where metrics from the upstream component will be
	// forwarded.
	collector := lazycollector.New()
	opts.Registerer.MustRegister(collector)

	r := &Auth{
		ctx:    ctx,
		cancel: cancel,

		opts:    opts,
		factory: f,

		sched:     scheduler.New(opts.Logger),
		collector: collector,
	}
	if err := r.Update(args); err != nil {
		return nil, err
	}
	return r, nil
}

// Run starts the Auth component.
func (a *Auth) Run(ctx context.Context) error {
	defer a.cancel()
	return a.sched.Run(ctx)
}

// Update implements component.Component. It will convert the Arguments into
// configuration for OpenTelemetry Collector authentication extension
// configuration and manage the underlying OpenTelemetry Collector extension.
func (a *Auth) Update(args component.Arguments) error {
	rargs := args.(Arguments)

	host := scheduler.NewHost(
		a.opts.Logger,
		scheduler.WithHostExtensions(rargs.Extensions()),
		scheduler.WithHostExporters(rargs.Exporters()),
	)

	reg := prometheus.NewRegistry()
	a.collector.Set(reg)

	promExporter, err := sdkprometheus.New(sdkprometheus.WithRegisterer(reg), sdkprometheus.WithoutTargetInfo())
	if err != nil {
		return err
	}

	settings := otelextension.CreateSettings{
		TelemetrySettings: otelcomponent.TelemetrySettings{
			Logger: zapadapter.New(a.opts.Logger),

			TracerProvider: a.opts.Tracer,
			MeterProvider:  metric.NewMeterProvider(metric.WithReader(promExporter)),

			ReportComponentStatus: func(*otelcomponent.StatusEvent) error {
				return nil
			},
		},

		BuildInfo: otelcomponent.BuildInfo{
			Command:     os.Args[0],
			Description: "Grafana Agent",
			Version:     build.Version,
		},
	}

	extensionConfig, err := rargs.Convert()
	if err != nil {
		return err
	}

	// Create instances of the extension from our factory.
	var components []otelcomponent.Component

	ext, err := a.factory.CreateExtension(a.ctx, settings, extensionConfig)
	if err != nil {
		return err
	} else if ext != nil {
		components = append(components, ext)
	}

	// Inform listeners that our handler changed.
	a.opts.OnStateChange(Exports{
		Handler: Handler{
			ID:        otelcomponent.NewID(otelcomponent.Type(a.opts.ID)),
			Extension: ext,
		},
	})

	// Schedule the components to run once our component is running.
	a.sched.Schedule(host, components...)
	return nil
}

// CurrentHealth implements component.HealthComponent.
func (a *Auth) CurrentHealth() component.Health {
	return a.sched.CurrentHealth()
}