[v18] Add teleport debug metrics command

lib/client/debug/debug.go

@@ -201,6 +201,15 @@ func (c *Client) GetMetrics(ctx context.Context) (map[string]*dto.MetricFamily,
 	return metrics, nil
 }
 
+// GetRawMetrics returns unprocessed prometheus metrics from the /metrics endpoint.
+func (c *Client) GetRawMetrics(ctx context.Context) (io.ReadCloser, error) {
+	resp, err := c.do(ctx, http.MethodGet, url.URL{Path: "/metrics"}, nil)
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+	return resp.Body, nil
+}
+
 func (c *Client) do(ctx context.Context, method string, u url.URL, body []byte) (*http.Response, error) {
 	u.Scheme = "http"
 	u.Host = "debug"

tool/teleport/common/debug.go

@@ -24,6 +24,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"os"
 	"slices"
 	"strings"
 	"time"
@@ -46,6 +47,8 @@ type DebugClient interface {
 	CollectProfile(context.Context, string, int) ([]byte, error)
 	// GetReadiness checks if the instance is ready to serve requests.
 	GetReadiness(context.Context) (debugclient.Readiness, error)
+	// GetRawMetrics fetches the unprocessed Prometheus metrics.
+	GetRawMetrics(context.Context) (io.ReadCloser, error)
 	SocketPath() string
 }
 
@@ -196,6 +199,26 @@ func readyz(ctx context.Context, clt DebugClient) error {
 	return nil
 }
 
+// onMetrics fetches the current Prometheus metrics.
+func onMetrics(ctx context.Context, configPath string) error {
+	clt, dataDir, err := newDebugClient(configPath)
+	if err != nil {
+		return trace.Wrap(err)
+	}
+
+	metrics, err := clt.GetRawMetrics(ctx)
+	if err != nil {
+		return convertToReadableErr(err, dataDir, clt.SocketPath())
+	}
+	defer metrics.Close()
+
+	if _, err := io.Copy(os.Stdout, metrics); err != nil {
+		return trace.Wrap(err)
+	}
+
+	return nil
+}
+
 // newDebugClient initializes the debug client based on the Teleport
 // configuration. It also returns the data dir and socket path used.
 func newDebugClient(configPath string) (DebugClient, string, error) {

tool/teleport/common/teleport.go

@@ -618,6 +618,7 @@ func Run(options Options) (app *kingpin.Application, executedCommand string, con
 	collectProfilesCmd.Arg("PROFILES", fmt.Sprintf("Comma-separated profile names to be exported. Supported profiles: %s. Default: %s", strings.Join(slices.Collect(maps.Keys(debugclient.SupportedProfiles)), ","), strings.Join(defaultCollectProfiles, ","))).StringVar(&ccf.Profiles)
 	collectProfilesCmd.Flag("seconds", "For CPU and trace profiles, profile for the given duration (if set to 0, it returns a profile snapshot). For other profiles, return a delta profile. Default: 0").Short('s').Default("0").IntVar(&ccf.ProfileSeconds)
 	readyzCmd := debugCmd.Command("readyz", "Checks if the instance is ready to serve requests.")
+	metricsCmd := debugCmd.Command("metrics", "Fetches the cluster's Prometheus metrics.")
 
 	selinuxCmd := app.Command("selinux-ssh", "Commands related to SSH SELinux module.").Hidden()
 	selinuxCmd.Flag("config", fmt.Sprintf("Path to a configuration file [%v].", defaults.ConfigFilePath)).Short('c').ExistingFileVar(&ccf.ConfigFile)
@@ -813,6 +814,8 @@ Examples:
 		err = onCollectProfiles(ccf.ConfigFile, ccf.Profiles, ccf.ProfileSeconds)
 	case readyzCmd.FullCommand():
 		err = onReadyz(ctx, ccf.ConfigFile)
+	case metricsCmd.FullCommand():
+		err = onMetrics(ctx, ccf.ConfigFile)
 	case moduleSourceCmd.FullCommand():
 		if runtime.GOOS != "linux" {
 			break