Simple AWS Lambda logger that uses CloudWatch Embedded Metric Format to create custom CloudWatch metrics (TypeScript)

cw-metric.ts

// https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch_Embedded_Metric_Format_Specification.html

export function logCustomMetric(metric: {
  dimensions: {
    [key: string]: string;
  };
  namespace: string;
  metrics: {
    unit: Unit;
    name: string;
    value: number | number[];
  }[];
}) {
  if (metric.dimensions.length > 9) {
    throw new Error("More than 9 dimensions provided");
  }
  if (metric.metrics.length > 100) {
    throw new Error("More than 100 metric definitions provided");
  }
  const metricValues: { [key: string]: number | number[] } = {};
  for (let metricDef of metric.metrics) {
    if (metricValues[metricDef.name]) {
        throw new Error(`Metric with name "${metricDef.name}" already provided`);
    }
    Object.assign(metricValues, { [metricDef.name]: metricDef.value });
  }
  console.log(
    JSON.stringify(
      {
        ...metric.dimensions,
        ...metricValues,
        _aws: {
          Timestamp: Date.now(),
          CloudWatchMetrics: [
            {
              Dimensions: [Object.keys(metric.dimensions)],
              Metrics: metric.metrics.map((metricDef) => ({
                Name: metricDef.name,
                Unit: metricDef.unit,
              })),
              Namespace: metric.namespace,
            },
          ],
        },
      },
      null,
      2
    )
  );
}

export enum Unit {
  Seconds = "Seconds",
  Microseconds = "Microseconds",
  Milliseconds = "Milliseconds",
  Bytes = "Bytes",
  Kilobytes = "Kilobytes",
  Megabytes = "Megabytes",
  Gigabytes = "Gigabytes",
  Terabytes = "Terabytes",
  Bits = "Bits",
  Kilobits = "Kilobits",
  Megabits = "Megabits",
  Gigabits = "Gigabits",
  Terabits = "Terabits",
  Percent = "Percent",
  Count = "Count",
  BytesPerSecond = "Bytes/Second",
  KilobytesPerSecond = "Kilobytes/Second",
  MegabytesPerSecond = "Megabytes/Second",
  GigabytesPerSecond = "Gigabytes/Second",
  TerabytesPerSecond = "Terabytes/Second",
  BitsPerSecond = "Bits/Second",
  KilobitsPerSecond = "Kilobits/Second",
  MegabitsPerSecond = "Megabits/Second",
  GigabitsPerSecond = "Gigabits/Second",
  TerabitsPerSecond = "Terabits/Second",
  CountPerSecond = "Count/Second",
  None = "None",
}