googleapis/mcp-toolbox · error

failed to unmarshal cluster JSON: %w

Error message

failed to unmarshal cluster JSON: %w

What it means

Thrown by GetCluster when json.Unmarshal fails to decode the marshaled cluster JSON into a map[string]any. Since the input came from protojson.Marshal, this is nearly always a sign of empty/invalid intermediate data rather than malformed cluster content.

Source

Thrown at internal/sources/dataproc/dataproc.go:244

	req := &dataprocpb.GetClusterRequest{
		ProjectId:   s.Project,
		Region:      s.Region,
		ClusterName: clusterName,
	}

	clusterPb, err := client.GetCluster(ctx, req)
	if err != nil {
		return nil, fmt.Errorf("failed to get cluster: %w", err)
	}

	jsonBytes, err := protojson.Marshal(clusterPb)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal cluster to JSON: %w", err)
	}

	var result map[string]any
	if err := json.Unmarshal(jsonBytes, &result); err != nil {
		return nil, fmt.Errorf("failed to unmarshal cluster JSON: %w", err)
	}

	consoleUrl := ClusterConsoleURLFromProto(clusterPb, s.Region)
	logsUrl := ClusterLogsURLFromProto(clusterPb, s.Region)

	wrappedResult := map[string]any{
		"consoleUrl": consoleUrl,
		"logsUrl":    logsUrl,
		"cluster":    result,
	}

	return wrappedResult, nil
}

// ListJobsResponse is the response from the list jobs API.
type ListJobsResponse struct {
	Jobs          []Job  `json:"jobs"`
	NextPageToken string `json:"nextPageToken"`

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Log/inspect jsonBytes when this fires to confirm what was produced by protojson.Marshal.
2. Update google.golang.org/protobuf and the dataproc module to latest versions.
3. Replace the two-step protojson->JSON->map conversion with a single protojson.Marshal into a struct if customizing the code.

null

if len(jsonBytes) == 0 || !json.Valid(jsonBytes) {
    return errors.New("invalid JSON produced from cluster proto")
}

cluster, err := src.GetCluster(ctx, name)
if err != nil && strings.Contains(err.Error(), "unmarshal cluster JSON") {
    // internal serialization issue: capture jsonBytes, update deps, report upstream
    return err
}

When it happens

Trigger: json.Unmarshal(jsonBytes, &result) receiving empty or non-JSON bytes — only realistically possible if the protojson.Marshal step produced invalid output or jsonBytes was mutated.

Common situations: Version-skew bugs in serialization; custom builds with modified code; effectively unreachable in normal operation given the preceding marshal succeeded.

Understand the failure class

Background: "failed to unmarshal" / json.Unmarshal errors: why parsing a response into a Go struct fails and how to fix it — this error's family across 23 libraries.

Related errors

• failed to unmarshal job JSON: %w
• failed to marshal result: %w
• operation finished with error but could not marshal error ob
• failed to unmarshal operation bytes: %w
• failed to marshal request: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/06fe6c25eade480e. Report an issue: GitHub.