Metric-Based Logging — Generating Business Metrics from Logs

// Log-based metric extraction
class LogMetricExtractor {
  constructor() {
    this.extractors = {
      'scan.completed': (entry) => ({
        metric: 'scans_completed',
        value: 1,
        tags: { scanType: entry.context?.scanType, status: entry.context?.status }
      }),
      'scan.duration': (entry) => ({
        metric: 'scan_duration_ms',
        value: entry.context?.duration,
        tags: { scanType: entry.context?.scanType }
      }),
      'file.uploaded': (entry) => ({
        metric: 'file_size_bytes',
        value: entry.context?.fileSize,
        tags: { fileType: entry.context?.fileType }
      }),
      'user.login': (entry) => ({
        metric: 'user_logins',
        value: 1,
        tags: { method: entry.context?.authMethod, result: entry.result }
      })
    };
  }

  async processLogEntry(entry) {
    const extractor = this.extractors[entry.type];
    if (!extractor) return;

    const metric = extractor(entry);
    await this.emitMetric(metric);
  }

  async emitMetric(metric) {
    // Emit to Prometheus
    prometheusClient.histogram(metric.metric, metric.value, metric.tags);

    // Emit to StatsD
    statsdClient.increment(metric.metric, metric.tags);
  }

  async generateBusinessReport(period) {
    const report = {
      totalScans: await this.queryMetric('scans_completed', period),
      averageDuration: await this.queryMetric('scan_duration_ms', period),
      topFileTypes: await this.queryTopTags('file_size_bytes', 'fileType', period),
      loginSuccessRate: await this.calculateSuccessRate('user_logins', period)
    };
    return report;
  }
}

// Dashboard queries
app.get('/metrics/business', async (req, res) => {
  const period = req.query.period || '24h';
  const report = await metricExtractor.generateBusinessReport(period);
  res.json(report);
});