What causes "failed to start logging: %v" in grpc/grpc-go?

Diagnose the inner %v exactly as for error 250 (ADC, project_id, network, Cloud Logging API).

failed to start logging

Error message

failed to start logging: %v

What it means

observability.Start called startLogging and it failed; the wrapped %v is error 252 (which itself wraps error 250, the Cloud Logging client error). Deferred End() runs to clean up. Emitted at observability.go:76.

Solutions

Diagnose the inner %v exactly as for error 250 (ADC, project_id, network, Cloud Logging API).
If logging is optional, remove cloud_logging from the config so Start proceeds without it.
Re-run Start in a fresh process after fixing credentials.
Log the full error chain so the underlying gcplogging.NewClient error is visible.

Example fix

// before
{"project_id":"","cloud_logging":{}}

// after
{"project_id":"my-proj","cloud_logging":{}}

Defensive patterns

Strategy: try-catch

Validate before calling

// Reuse the error 250 pre-flight: ensure logging client builds before Start.
if _, err := gcplogging.NewClient(ctx, "projects/"+projectID); err != nil {
    return fmt.Errorf("logging unavailable; remove cloud_logging or fix env: %w", err)
}

Try / catch

if err := observability.Start(ctx); err != nil {
    if strings.Contains(err.Error(), "failed to start logging") {
        log.Fatalf("logging subsystem failed to start (see inner exporter error): %v", err)
    }
    return err
}

Prevention

Make logging optional in your config schema so Start can proceed without it.
Surface the inner error from 250/252 in logs.
Re-run Start in a fresh process after fixing credentials.

When it happens

Trigger: Config has a cloud_logging block but the Cloud Logging exporter could not be built or initialized. Same root causes as error 250/252: bad ADC, bad project, network blocked, API disabled.

Common situations: Same production-deploy failures as 250/252; surfaces here when only the top-level Start error is logged. Often accompanied by 254 if tracing/metrics are also enabled and ADC is the root cause.

Related errors

AI-assisted analysis of grpc/grpc-go@0c51461d27 (2026-08-11). Data as JSON: /api/errors/57818c140066ef98. Report an issue: GitHub.

Appendix: source

Thrown at gcp/observability/observability.go:76

	if err = ensureProjectIDInObservabilityConfig(ctx, config); err != nil {
		return err
	}

	// Cleanup any created resources this function created in case this function
	// errors.
	defer func() {
		if err != nil {
			End()
		}
	}()

	// Enabling tracing and metrics via OpenCensus
	if err = startOpenCensus(config); err != nil {
		return fmt.Errorf("failed to instrument OpenCensus: %v", err)
	}

	if err = startLogging(ctx, config); err != nil {
		return fmt.Errorf("failed to start logging: %v", err)
	}

	// Logging is controlled by the config at methods level.
	return nil
}

// End is the clean-up API for gRPC Observability plugin. It is expected to be
// invoked in the main function of the application. The suggested usage is
// "defer observability.End()". This function also flushes data to upstream, and
// cleanup resources.
//
// Note: this method should only be invoked once.
func End() {
	stopLogging()
	stopOpenCensus()
}

View on GitHub (pinned to 0c51461d27)