VictoriaMetrics/VictoriaMetrics · error

cannot parse MetricPost object: %w

Error message

cannot parse MetricPost object: %w

What it means

This is the outer wrapper returned by Unmarshal for any error that occurred while processing a MetricPost object inside the Visit callback (Events array errors, EventObject errors, row unmarshal errors). It wraps an inner error, so the root cause is always in the wrapped chain. It marks the request body as unparseable at one of the MetricPost objects.

Source

Thrown at lib/protoparser/newrelic/parser.go:84

						err = fmt.Errorf("cannot find EventObject: %w", errLocal)
						return
					}
					if cap(rows) > len(rows) {
						rows = rows[:len(rows)+1]
					} else {
						rows = append(rows, Row{})
					}
					r := &rows[len(rows)-1]
					if errLocal := r.unmarshal(eventObject); errLocal != nil {
						err = fmt.Errorf("cannot unmarshal EventObject: %w", errLocal)
						return
					}
				}
			}
		})
		r.Rows = rows
		if err != nil {
			return fmt.Errorf("cannot parse MetricPost object: %w", err)
		}
	}
	return nil
}

// Row represents parsed row
type Row struct {
	Tags      []Tag
	Samples   []Sample
	Timestamp int64
}

// Tag represents a key=value tag
type Tag struct {
	Key   []byte
	Value []byte
}

View on GitHub (pinned to 5079fb58f1)

Solutions

1. Read the wrapped inner error (%w chain) to identify the exact field and cause.
2. Validate the payload structure: [{"Events": [{...event fields...}]}].
3. Use a JSON schema validator on the body before posting.
4. Fix the client that produced the malformed MetricPost object.

Example fix

// before
{"Events": [{"timestamp": "not-a-number"}]}
// after
{"Events": [{"eventType": "Foo", "timestamp": 1690000000}]}

func validatePayload(body []byte) error {
	var posts []map[string]json.RawMessage
	if err := json.Unmarshal(body, &posts); err != nil {
		return fmt.Errorf("invalid MetricPost array: %w", err)
	}
	return nil
}

func isMetricPostArray(v interface{}) bool {
	arr, ok := v.([]interface{})
	if !ok {
		return false
	}
	for _, e := range arr {
		if _, ok := e.(map[string]interface{}); !ok {
			return false
		}
	}
	return true
}

if err := rows.Unmarshal(body); err != nil {
	var inner error
	for e := err; e != nil; e = errors.Unwrap(e) {
		inner = e
	}
	log.Printf("MetricPost parse failed, root cause: %v (chain: %v)", inner, err)
	return err
}

When it happens

Trigger: Any of: 'Events' value not an array; an Events element not an object; Row.unmarshal failing (bad timestamp) — for any MetricPost in the top-level array.

Common situations: Malformed payloads from misconfigured NewRelic agents, custom exporters, or intermediaries that transform the body; debugging a 400 response from the NewRelic import endpoint.

Related errors

• cannot find MetricPost object: %w
• cannot find Events array in MetricPost object: %w
• cannot find EventObject: %w
• cannot unmarshal EventObject: %w
• cannot parse `timestamp` field: %w

AI-assisted analysis of VictoriaMetrics/VictoriaMetrics@5079fb58f1 (2026-09-03). Data as JSON: /api/errors/d6c6c04a07d349b4. Report an issue: GitHub.