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Target Module

The target module is the core of the Ping. It handles the external APIs to be monitored. An API that is registered with this module is called a Target. Every Target has a unique URL and a configurable interval between checks. The entire Ping engine is built around the concept of a Target.

This module is responsible for registering new targets, retrieving information about existing targets, and deleting existing targets.

This module is implemented in the src/modules/target directory.

Key Functions

  • createTarget: Registers a new API ('Target') for monitoring.
  • getTargets: Retrieves a list of all registered targets whether they are active or not.
  • removeTarget(id): Permanently deletes a target by id and stops its monitoring loop.
  • getActiveTargets: Retrieves a list of all active targets for use by the scheduler.

Technical Details

Target Module

This module is responsible for registering new targets, retrieving information about existing targets, and deleting existing targets.

The target module is the core of the Ping. It handles the external APIs to be monitored.It ensures data integrity through strict Zod validation and Mongoose schema constraints. An API that is registered with this module is called a Target. Every Target has a unique URL and a configurable interval between checks. The entire Ping engine is built around the concept of a Target.

This module is implemented in the src/modules/target directory.

API Routes

  • GET /health: Verifies the target router is active.
  • POST /targets: Registers a new monitoring target. Requires a name, valid URL, and interval.
  • GET /targets: Returns a list of all configured targets.
  • DELETE /targets/:id: Removes a target from the system via its unique ID.

Public Service Interface

The target.service.js handles the core business logic:

  • createTarget(): Normalizes strings, checks for name collisions, and persists the target.
  • getTargets(): Returns all targets as plain JavaScript objects (.lean()).
  • getActiveTargets(): Specifically filters for targets where active: true.
  • removeTarget(id): Handles deletion and returns the deleted document or null.

Data Model & Schema

  • Collection: targets
  • Schema Highlights:
    • url: Must be unique; the primary address to be probed.
    • intervalSeconds: A positive integer defining how often the check runs.
    • lastCheckedAt: Automatically updated by the execution engine (Check module).
    • timestamps: Tracks createdAt and updatedAt for auditing.

Technical Constraints

  • Validation: Enforced by Zod. URLs must follow standard web formats, and IDs must be 24-character hexadecimal strings.
  • Normalization: Logic in the service layer trims whitespace from name and url before processing.
  • Uniqueness: The system prevents duplicate name entries via service-level checks and duplicate url entries via MongoDB indexes.

Dependencies

  • Middleware: Uses the global validate middleware to intercept invalid requests before they hit controllers.
  • Database: Heavily dependent on MongoDB/Mongoose for persistence and query execution.

Error Handling

  • Validation Errors: Returns a 400 Bad Request with specific field issues via Zod.
  • Conflict Errors: Throws an error if a target name is already taken.
  • Not Found: Returns a 404 status if a DELETE request provides an ID that doesn't exist.
  • Generic Failures: Errors are passed to next(err) to be handled by the global Express error middleware.

Usage Example

import { createTarget } from "./target.service.js";

const target = await createTarget({
  name: "Google Search",
  url: "https://google.com",
  intervalSeconds: 30,
});

console.log(`Target created: ${target.name}`);