u

src/services/healthMonitorService.js

@@ -0,0 +1,181 @@
+// #region Imports & Configuration
+import http from 'node:http';
+import Redis from 'ioredis';
+import env from '../config/env.js';
+import { createLogger } from '../util/logger.js';
+
+const healthLog = createLogger('health-monitor');
+
+let scheduledTimer = null;
+let scheduledInterval = null;
+let isServiceRunning = false;
+let redisClient = null;
+// #endregion
+
+// #region Redis Client Management
+// MARK: resolves or creates the lazy Redis client
+export function getRedisClient() {
+    if (!redisClient) {
+        const opts = env.redis.url
+            ? env.redis.url
+            : {
+                host: env.redis.host,
+                port: env.redis.port,
+                password: env.redis.password || undefined,
+                db: env.redis.db || 0,
+                lazyConnect: true,
+                enableReadyCheck: false,
+                maxRetriesPerRequest: 1,
+                retryStrategy(times) {
+                    return Math.min(times * 1000, 30000);
+                },
+            };
+
+        redisClient = new Redis(opts);
+        redisClient.on('error', (err) => {
+            healthLog.warn(`Redis connection error: ${err.message}`);
+        });
+    }
+    return redisClient;
+}
+// #endregion
+
+// #region TCP Health API Selftest
+// MARK: executes an HTTP GET /health call over TCP loopback and measures response time
+export function performHealthSelftest() {
+    return new Promise((resolve, reject) => {
+        const start = performance.now();
+        const req = http.request(
+            {
+                hostname: '127.0.0.1',
+                port: env.port,
+                path: '/health',
+                method: 'GET',
+                headers: {
+                    'User-Agent': 'Dashback-HealthMonitor/1.0',
+                    'Accept': 'application/json',
+                },
+                timeout: 10000,
+            },
+            (res) => {
+                let data = '';
+                res.on('data', (chunk) => {
+                    data += chunk;
+                });
+                res.on('end', () => {
+                    const durationMs = Math.round((performance.now() - start) * 100) / 100;
+                    if (res.statusCode >= 200 && res.statusCode < 300) {
+                        resolve({ success: true, durationMs, statusCode: res.statusCode, body: data });
+                    } else {
+                        resolve({ success: false, durationMs, statusCode: res.statusCode, body: data });
+                    }
+                });
+            }
+        );
+
+        req.on('error', (err) => {
+            const durationMs = Math.round((performance.now() - start) * 100) / 100;
+            reject({ error: err, durationMs });
+        });
+
+        req.on('timeout', () => {
+            req.destroy(new Error('TCP connection or request timed out'));
+        });
+
+        req.end();
+    });
+}
+
+// MARK: runs one selftest cycle and writes duration to Redis
+async function executeHealthCheckCycle() {
+    try {
+        const result = await performHealthSelftest();
+        if (result.success) {
+            try {
+                const redis = getRedisClient();
+                await redis.set(env.redis.key, String(result.durationMs));
+                healthLog.debug(
+                    `Health selftest passed in ${result.durationMs}ms; recorded in redis key "${env.redis.key}"`
+                );
+            } catch (redisErr) {
+                healthLog.warn(`Failed to write latency to Redis: ${redisErr.message}`);
+            }
+        } else {
+            healthLog.warn(
+                `Health selftest returned HTTP ${result.statusCode} in ${result.durationMs}ms`
+            );
+        }
+    } catch (err) {
+        const msg = err?.error?.message || err?.message || String(err);
+        healthLog.warn(`Health selftest failed: ${msg}`);
+    }
+}
+// #endregion
+
+// #region Service Lifecycle
+// MARK: starts the periodic health check selftest service
+export function startHealthMonitorService() {
+    if (isServiceRunning) return;
+    if (env.healthMonitor?.enabled === false) {
+        healthLog.info('Health monitor service is disabled by configuration.');
+        return;
+    }
+
+    isServiceRunning = true;
+    const intervalMs = env.healthMonitor?.intervalMs || 60_000;
+
+    // Run initial selftest after 1s warmup
+    scheduledTimer = setTimeout(() => {
+        scheduledTimer = null;
+        executeHealthCheckCycle().catch((err) => {
+            healthLog.error(`Initial health selftest error: ${err.message}`);
+        });
+    }, 1000);
+
+    // Schedule recurring selftest every minute
+    scheduledInterval = setInterval(() => {
+        executeHealthCheckCycle().catch((err) => {
+            healthLog.error(`Recurring health selftest error: ${err.message}`);
+        });
+    }, intervalMs);
+
+    healthLog.info(`Health monitor service started (selftest every ${Math.round(intervalMs / 1000)}s via TCP).`);
+}
+
+// MARK: stops the health check service and closes Redis client
+export async function stopHealthMonitorService() {
+    isServiceRunning = false;
+    if (scheduledTimer) {
+        clearTimeout(scheduledTimer);
+        scheduledTimer = null;
+    }
+    if (scheduledInterval) {
+        clearInterval(scheduledInterval);
+        scheduledInterval = null;
+    }
+
+    if (redisClient) {
+        try {
+            await redisClient.quit();
+        } catch {
+            redisClient.disconnect();
+        } finally {
+            redisClient = null;
+        }
+    }
+
+    healthLog.info('Health monitor service stopped.');
+}
+
+// MARK: returns health monitor status
+export function getHealthMonitorStatus() {
+    return {
+        enabled: env.healthMonitor?.enabled ?? true,
+        isRunning: isServiceRunning,
+        intervalMs: env.healthMonitor?.intervalMs || 60_000,
+        redisKey: env.redis.key,
+        redisHost: env.redis.host,
+        redisPort: env.redis.port,
+    };
+}
+// #endregion