@aws-lambda-powertools/metrics/lib/cjs/middleware/middy.js

The metrics package for the Powertools for AWS Lambda (TypeScript) library

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.logMetrics = void 0;
const commons_1 = require("@aws-lambda-powertools/commons");
/**
 * A Middy.js middleware automating capture of Amazon CloudWatch metrics.
 *
 * This middleware is compatible with `@middy/core@3.x` and above.
 *
 * The middleware automatically flushes metrics after the handler function returns or throws an error,
 * so you don't need to call {@link Metrics.publishStoredMetrics | `publishStoredMetrics()`} manually.
 *
 * @example
 * ```typescript
 * import { Metrics, MetricUnit } from '@aws-lambda-powertools/metrics';
 * import { logMetrics } from '@aws-lambda-powertools/metrics/middleware';
 * import middy from '@middy/core';
 *
 * const metrics = new Metrics({
 *   namespace: 'serverlessAirline',
 *   serviceName: 'orders'
 * });
 *
 * export const handler = middy(async () => {
 *   metrics.addMetadata('request_id', event.requestId);
 *   metrics.addMetric('successfulBooking', MetricUnit.Count, 1);
 * }).use(logMetrics(metrics, {
 *   captureColdStartMetric: true,
 *   throwOnEmptyMetrics: true,
 * }));
 * ```
 *
 * You can configure the middleware with the following options:
 * - `captureColdStartMetric`: Whether to capture a `ColdStart` metric
 * - `defaultDimensions`: Default dimensions to add to all metrics
 * - `throwOnEmptyMetrics`: Whether to throw an error if no metrics are emitted
 *
 * @param target - The Metrics instance to use for emitting metrics
 * @param options - Options to configure the middleware, see {@link ExtraOptions}
 */
const logMetrics = (target, options = {}) => {
    const metricsInstances = Array.isArray(target) ? target : [target];
    /**
     * Set the cleanup function to be called in case other middlewares return early.
     *
     * @param request - The request object
     */
    const setCleanupFunction = (request) => {
        request.internal = {
            ...request.internal,
            [commons_1.METRICS_KEY]: logMetricsAfterOrError,
        };
    };
    const logMetricsBefore = (request) => {
        for (const metrics of metricsInstances) {
            const { throwOnEmptyMetrics, defaultDimensions, captureColdStartMetric } = options;
            if (throwOnEmptyMetrics) {
                metrics.setThrowOnEmptyMetrics(throwOnEmptyMetrics);
            }
            if (defaultDimensions !== undefined) {
                metrics.setDefaultDimensions(defaultDimensions);
            }
            if (captureColdStartMetric) {
                metrics.captureColdStartMetric(request.context.functionName);
            }
        }
        setCleanupFunction(request);
    };
    const logMetricsAfterOrError = () => {
        for (const metrics of metricsInstances) {
            metrics.publishStoredMetrics();
        }
    };
    return {
        before: logMetricsBefore,
        after: logMetricsAfterOrError,
        onError: logMetricsAfterOrError,
    };
};
exports.logMetrics = logMetrics;