grafana/k6 · error · ErrMetricNameParsing

%w, metric %q closing curly brace appears before opening one

Error message

%w, metric %q closing curly brace appears before opening one

What it means

Raised by ParseMetricName when a '}' appears before the matching '{' in a metric name with tag filters, making the expression malformed. Wraps the ErrMetricNameParsing sentinel.

Source

Thrown at metrics/metric.go:115

	// are present, thus the metric name only consists of a literal.
	if !containsOpeningToken && !containsClosingToken {
		return name, nil, nil
	}

	// If the name contains an opening or closing token, but not
	// its counterpart, the expression is malformed.
	if (containsOpeningToken && !containsClosingToken) ||
		(!containsOpeningToken && containsClosingToken) {
		return "", nil, fmt.Errorf(
			"%w, metric %q has unmatched opening/close curly brace",
			ErrMetricNameParsing, name,
		)
	}

	// If the closing brace token appears before the opening one,
	// the expression is malformed
	if closingTokenPos < openingTokenPos {
		return "", nil, fmt.Errorf("%w, metric %q closing curly brace appears before opening one", ErrMetricNameParsing, name)
	}

	// If the last character is not a closing brace token,
	// the expression is malformed.
	if closingTokenPos != (len(name) - 1) {
		err := fmt.Errorf(
			"%w, metric %q lacks a closing curly brace in its last position",
			ErrMetricNameParsing,
			name,
		)
		return "", nil, err
	}

	// We already know the position of the opening and closing curly brace
	// tokens. Thus, we extract the string in between them, and split its
	// content to obtain the tags key values.
	tags := strings.Split(name[openingTokenPos+1:closingTokenPos], ",")

View on GitHub (pinned to 01ffac6f24)

Solutions

1. Order the braces correctly: name first, then tags, e.g. my_metric{tag:value}

When it happens

Trigger: Thrown at metrics/metric.go:115 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grafana/k6@01ffac6f24 (2026-08-18). Data as JSON: /api/errors/8bad8c5719b05267. Report an issue: GitHub.