Method asPrometheus

coderd/prometheusmetrics/aggregator.go:442–475

asPrometheus returns the annotatedMetric as a prometheus.Metric, it preallocates/fills by index, uses the aggregators metric description cache, and a small stack buffer for values in order to reduce memory allocations.

(am *annotatedMetric)

// asPrometheus returns the annotatedMetric as a prometheus.Metric, it preallocates/fills by index, uses the aggregators
// metric description cache, and a small stack buffer for values in order to reduce memory allocations.
func (ma *MetricsAggregator) asPrometheus(am *annotatedMetric) (prometheus.Metric, error) {
	baseLabelNames := am.aggregateByLabels
	extraLabels := am.Labels

	nBase := len(baseLabelNames)
	nExtra := len(extraLabels)
	nTotal := nBase + nExtra

	var scratch [16]string
	var labelValues []string
	if nTotal <= len(scratch) {
		labelValues = scratch[:nTotal]
	} else {
		labelValues = make([]string, nTotal)
	}

	for i, label := range baseLabelNames {
		val, err := am.getFieldByLabel(label)
		if err != nil {
			return nil, err
		}
		labelValues[i] = val
	}
	for i, l := range extraLabels {
		labelValues[nBase+i] = l.Value
	}

	desc := ma.getOrCreateDesc(am.Name, metricHelpForAgent, baseLabelNames, extraLabels)
	valueType, err := asPrometheusValueType(am.Type)
	if err != nil {
		return nil, err
	}
	return prometheus.MustNewConstMetric(desc, valueType, am.Value, labelValues...), nil
}

var defaultAgentMetricsLabels = []string{agentmetrics.LabelUsername, agentmetrics.LabelWorkspaceName, agentmetrics.LabelAgentName, agentmetrics.LabelTemplateName}