express-healthcheck-endpoints/lib/registry.js

Basic health check provider for Express.js applications. It allows you to register health checks and provides custom ways to retrieve the health status of your application.

import { healthStatusValues, healthStatusCodes } from "./healthEnums.js";
class HealthCheckRegistry {
  constructor() {
    this.checks = new Map();
  }
  register(name, healthCheck) {
    if (this.checks.has(name)) {
      throw new Error(`Health check with name '${name}' is already registered.`);
    }
    this.checks.set(name, healthCheck);
  }
  getResults() {
    return Array.from(this.checks.entries()).map(async ([name, check]) => ({
      [name]: await check.mapToObject()
    }));
  }
  getOverallStatusResponse(healthChecks) {
    // Determine overall status
    const areAllUnknown = healthChecks.length === 0 || healthChecks.every(r => r.isUnknown());
    const hasUnhealthy = healthChecks.some(r => r.isUnhealthy());
    let overallStatus = healthStatusValues.healthy;
    let overallStatusCode = healthStatusCodes.healthy;
    if (areAllUnknown) {
      overallStatus = healthStatusValues.unknown;
      overallStatusCode = healthStatusCodes.unknown;
    } else if (hasUnhealthy) {
      overallStatus = healthStatusValues.unhealthy;
      overallStatusCode = healthStatusCodes.unhealthy;
    }
    return {
      overallStatus,
      overallStatusCode
    };
  }
  async handler() {
    return async (_, res) => {
      const arrResults = await Promise.all(this.getResults());
      const results = Object.assign({}, ...arrResults);
      const healthChecks = Array.from(this.checks.values());
      const {
        overallStatus,
        overallStatusCode
      } = this.getOverallStatusResponse(healthChecks);
      return res.status(overallStatusCode).json({
        overallStatus,
        overallStatusCode,
        uptime: process.uptime(),
        results
      });
    };
  }
}
export default HealthCheckRegistry;