71 lines
2.4 KiB
TypeScript
71 lines
2.4 KiB
TypeScript
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import { Metric } from './metrics'
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function escapeString(str: string) {
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return str.replace(/\\/g, '\\\\').replace(/\n/g, '\\n')
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}
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/**
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* String Attribute values are converted directly to Prometheus attribute values.
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* Non-string values are represented as JSON-encoded strings.
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*
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* `undefined` is converted to an empty string.
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*/
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function escapeAttributeValue(str: string) {
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if (typeof str !== 'string') {
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str = JSON.stringify(str)
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}
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return escapeString(str).replace(/"/g, '\\"')
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}
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const invalidCharacterRegex = /[^a-z0-9_]/gi
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/**
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* Ensures metric names are valid Prometheus metric names by removing
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* characters allowed by OpenTelemetry but disallowed by Prometheus.
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*
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* https://prometheus.io/docs/concepts/data_model/#metric-names-and-attributes
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*
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* 1. Names must match `[a-zA-Z_:][a-zA-Z0-9_:]*`
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*
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* 2. Colons are reserved for user defined recording rules.
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* They should not be used by exporters or direct instrumentation.
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*
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* OpenTelemetry metric names are already validated in the Meter when they are created,
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* and they match the format `[a-zA-Z][a-zA-Z0-9_.\-]*` which is very close to a valid
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* prometheus metric name, so we only need to strip characters valid in OpenTelemetry
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* but not valid in prometheus and replace them with '_'.
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*
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* @param name name to be sanitized
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*/
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function sanitizePrometheusMetricName(name: string): string {
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return name.replace(invalidCharacterRegex, '_') // replace all invalid characters with '_'
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}
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export class MetricsRenderer {
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constructor(private readonly prefix: string) {}
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render(metric: Metric): string {
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const name = this.metricName(metric.name)
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return [
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`# TYPE ${name} ${name.endsWith('_total') ? 'count' : 'gauge'}`,
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`${name}${this.renderLabels(metric.labels)} ${metric.value}${
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metric.timestamp !== null ? ' ' + String(metric.timestamp.getTime()) : ''
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}`,
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].join('\n')
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}
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private renderLabels(labels: Metric['labels']): string {
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const rendered = Object.entries(labels)
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.map(([key, value]) => `${sanitizePrometheusMetricName(key)}="${escapeAttributeValue(value)}"`)
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.join(',')
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return rendered !== '' ? '{' + rendered + '}' : ''
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}
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private metricName(name: string): string {
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name = name.replace(/^(.*_)?(total)_(.*)$/, '$1$3_$2')
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return sanitizePrometheusMetricName(this.prefix.replace(/_+$/, '') + '_' + name)
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}
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}
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