What causes "unsupported tracer: %s" in micro/go-micro?

Correct the tracer name spelling to match the registered key (e.g. "jaeger").

unsupported tracer: %s

Error message

unsupported tracer: %s

What it means

The CLI rejects a --tracer value that has no registered constructor in c.opts.Tracers. Tracer plugins register themselves from their own packages; only linked tracers are selectable on the command line.

Source

Thrown at cmd/cmd.go:455

			*c.opts.Server = s()
		}
	}

	// Set the store
	if name := ctx.String("store"); len(name) > 0 {
		s, ok := c.opts.Stores[name]
		if !ok {
			return fmt.Errorf("store %q is not linked into this binary: import go-micro.dev/v6/cmd/defaults to enable flag-selected plugins", name)
		}

		*c.opts.Store = s(store.WithClient(*c.opts.Client))
	}

	// Set the tracer
	if name := ctx.String("tracer"); len(name) > 0 {
		r, ok := c.opts.Tracers[name]
		if !ok {
			return fmt.Errorf("unsupported tracer: %s", name)
		}

		*c.opts.Tracer = r()
	}

	// Setup auth
	authOpts := []auth.Option{}

	if len(ctx.String("auth_id")) > 0 || len(ctx.String("auth_secret")) > 0 {
		authOpts = append(authOpts, auth.Credentials(
			ctx.String("auth_id"), ctx.String("auth_secret"),
		))
	}
	if len(ctx.String("auth_public_key")) > 0 {
		authOpts = append(authOpts, auth.PublicKey(ctx.String("auth_public_key")))
	}
	if len(ctx.String("auth_private_key")) > 0 {
		authOpts = append(authOpts, auth.PrivateKey(ctx.String("auth_private_key")))

View on GitHub (pinned to 24529f1404)

Solutions

Correct the tracer name spelling to match the registered key (e.g. "jaeger").
Import the tracer plugin package into your main (or go-micro.dev/v6/cmd/defaults if it includes it) and rebuild.
Omit --tracer to use the built-in no-op/default tracer.
Verify available tracers by checking which plugin packages your binary imports.

Example fix

// before
micro --tracer jaeger call ...
// after: link the plugin in main.go
import _ "go-micro.dev/v6/plugins/tracer/jaeger"
// or use the default:
micro call ...

Defensive patterns

Strategy: validation

Validate before calling

allowedTracers := map[string]bool{"": true, "jaeger": true /* linked ones */}
if !allowedTracers[*tracerFlag] {
    return fmt.Errorf("tracer %q not linked; import its plugin package", *tracerFlag)
}

Try / catch

if err := c.Run(ctx); err != nil {
    if strings.HasPrefix(err.Error(), "unsupported tracer:") {
        return fmt.Errorf("%w (link the tracer plugin package and rebuild)", err)
    }
    return err
}

Prevention

Import the tracer plugin package whenever you pass --tracer in configs/scripts.
Avoid copy-pasting tracer flags from docs without verifying availability in your build.
Run a startup self-check that validates all configured plugin flags before serving.

When it happens

Trigger: Passing --tracer jaeger (or zipkin, otel, etc.) to a binary that never imported the tracer plugin package, or misspelling the tracer name.

Common situations: Docs/examples referencing a tracer plugin that the deployment binary does not include; typos like --tracer jagger; custom binaries that import only core defaults without tracer plugins.

Related errors

AI-assisted analysis of micro/go-micro@24529f1404 (2026-09-01). Data as JSON: /api/errors/b278da492968b58e. Report an issue: GitHub.