@stoplight/moleculer/src/middlewares/fallback.js

Fast & powerful microservices framework for Node.JS

/*
 * moleculer
 * Copyright (c) 2018 MoleculerJS (https://github.com/moleculerjs/moleculer)
 * MIT Licensed
 */

"use strict";

const { MoleculerError } = require("../errors");
const { METRIC } = require("../metrics");
const { isFunction, isString } = require("../utils");

module.exports = function FallbackMiddleware(broker) {
	function handleContextFallback(ctx, err) {
		broker.logger.warn(
			`The '${ctx.action.name}' request is failed. Return fallback response.`,
			{ requestID: ctx.requestID, err: err.message }
		);
		broker.metrics.increment(METRIC.MOLECULER_REQUEST_FALLBACK_TOTAL, {
			action: ctx.action.name
		});
		ctx.fallbackResult = true;

		if (isFunction(ctx.options.fallbackResponse)) return ctx.options.fallbackResponse(ctx, err);
		else return Promise.resolve(ctx.options.fallbackResponse);
	}

	function wrapFallbackMiddleware(handler, action) {
		return function fallbackMiddleware(ctx) {
			// Call the handler
			return handler(ctx).catch(err => {
				// Handle fallback response from calling options
				if (ctx.options.fallbackResponse) {
					return handleContextFallback(ctx, err);
				}

				// Handle fallback from Action Definition (only locally)
				if (action.fallback && action.service) {
					const svc = action.service;

					const fallback = isString(action.fallback)
						? svc[action.fallback]
						: action.fallback;
					if (!isFunction(fallback)) {
						/* istanbul ignore next */
						throw new MoleculerError(
							`The 'fallback' of '${action.name}' action is not a Function or valid method name: ${action.fallback}`
						);
					}

					svc.logger.warn(
						`The '${ctx.action.name}' request is failed. Return fallback response.`,
						{ requestID: ctx.requestID, err: err.message }
					);
					broker.metrics.increment(METRIC.MOLECULER_REQUEST_FALLBACK_TOTAL, {
						service: svc.fullName,
						action: action.name
					});
					ctx.fallbackResult = true;

					return fallback.call(svc, ctx, err);
				}

				return Promise.reject(err);
			});
		}.bind(this);
	}

	return {
		name: "Fallback",

		created(broker) {
			if (broker.isMetricsEnabled()) {
				broker.metrics.register({
					name: METRIC.MOLECULER_REQUEST_FALLBACK_TOTAL,
					type: METRIC.TYPE_COUNTER,
					labelNames: ["service", "action"],
					description: "Number of fallbacked requests",
					rate: true
				});
			}
		},

		localAction: wrapFallbackMiddleware,
		remoteAction: wrapFallbackMiddleware

		/*call(next) {
			return (actionName, params, opts) => {
				return next(actionName, params, opts).catch(err => {
					if (opts.fallbackResponse) {
						return handleContextFallback(null, err);
					}
					throw err;
				});
			};
		},*/
	};
};