docker/compose · error

initializing otel connection from docker context metadata: %

Error message

initializing otel connection from docker context metadata: %w

What it means

With an OTLP endpoint configured via Docker context, compose builds a gRPC client with grpc.NewClient, a custom dialer restricted to local Unix sockets/named pipes (memnet.DialEndpoint), and insecure credentials. If client construction fails, tracing init returns 'initializing otel connection from docker context metadata: %w'. Note grpc.NewClient defers connection, so failures here are config-level (bad endpoint format), not connectivity.

Source

Thrown at internal/tracing/docker_context.go:72

			if err := os.Setenv(k, v); err != nil {
				panic(fmt.Errorf("restoring env for %q: %w", k, err))
			}
		}
	}()
	for k := range otelEnv {
		if err := os.Unsetenv(k); err != nil {
			return nil, fmt.Errorf("stashing env for %q: %w", k, err)
		}
	}

	conn, err := grpc.NewClient(cfg.Endpoint,
		grpc.WithContextDialer(memnet.DialEndpoint),
		// this dial is restricted to using a local Unix socket / named pipe,
		// so there is no need for TLS
		grpc.WithTransportCredentials(insecure.NewCredentials()),
	)
	if err != nil {
		return nil, fmt.Errorf("initializing otel connection from docker context metadata: %w", err)
	}

	client := otlptracegrpc.NewClient(otlptracegrpc.WithGRPCConn(conn))
	return client, nil
}

// ConfigFromDockerContext inspects extra metadata included as part of the
// specified Docker context to try and extract a valid OTLP client configuration.
func ConfigFromDockerContext(st store.Store, name string) (OTLPConfig, error) {
	meta, err := st.GetMetadata(name)
	if err != nil {
		return OTLPConfig{}, err
	}

	var otelCfg any
	switch m := meta.Metadata.(type) {
	case command.DockerContext:
		otelCfg = m.AdditionalFields[otelConfigFieldName]

View on GitHub (pinned to ddc4b044b6)

Solutions

1. Fix the endpoint format in the Docker context metadata: use a gRPC target such as unix:///var/run/docker-desktop_OTLP.sock or host:port without a scheme
2. docker context export <name> (or edit meta.json) to inspect the otel.OTEL_EXPORTER_OTLP_ENDPOINT value and correct it
3. If you do not want context-based tracing, remove the otel field from the context metadata so cfg.Endpoint is empty and this path is skipped
4. Validate with: docker context inspect <name> --format '{{json .AdditionalFields}}'

Example fix

// ~/.docker/contexts/meta/<hash>/meta.json
// before: "otel": {"OTEL_EXPORTER_OTLP_ENDPOINT": "http://localhost:4317"}
// after:  "otel": {"OTEL_EXPORTER_OTLP_ENDPOINT": "localhost:4317"}

// validate the endpoint shape before it reaches grpc.NewClient
func validGRPCTarget(ep string) bool {
    return !strings.HasPrefix(ep, "http://") && !strings.HasPrefix(ep, "https://") &&
        (strings.HasPrefix(ep, "unix://") || regexp.MustCompile(`^[A-Za-z0-9._~-]+(:\d+)?$`).MatchString(ep))
}

null // endpoint arrives as untyped JSON from context metadata

// on this wrap, docker context inspect the otel block, fix the endpoint format (no http:// scheme), retry once

When it happens

Trigger: cfg.Endpoint from the Docker context 'otel' field being unparseable as a gRPC target — e.g. 'http://localhost:4317' instead of 'unix:///...' or 'localhost:4317' with an invalid authority component — causing grpc.NewClient to return err before any dial.

Common situations: Hand-editing the Docker context meta.json to add an otel block with an HTTP URL or typo'd endpoint; Docker Desktop writing an endpoint scheme the gRPC resolver rejects; endpoints with spaces or invalid characters.

Related errors

• loading otel config from docker context metadata: %w
• unexpected type for field %q: %T (expected: %T)
• restoring env for %q: %w
• stashing env for %q: %w
• failed to create resource: %w

AI-assisted analysis of docker/compose@ddc4b044b6 (2026-08-15). Data as JSON: /api/errors/41544753aee04ba2. Report an issue: GitHub.