Add in-memory caching strategy for aggregated queries with TTL and automatic invalidation on data changes

server/cache.js

@@ -0,0 +1,54 @@
+// Simple in-memory cache with TTL support
+class CacheManager {
+  constructor() {
+    this.cache = new Map();
+  }
+
+  set(key, value, ttlSeconds = 300) {
+    const expiresAt = Date.now() + (ttlSeconds * 1000);
+    this.cache.set(key, { value, expiresAt });
+  }
+
+  get(key) {
+    const item = this.cache.get(key);
+    if (!item) return null;
+    
+    if (Date.now() > item.expiresAt) {
+      this.cache.delete(key);
+      return null;
+    }
+    
+    return item.value;
+  }
+
+  has(key) {
+    return this.get(key) !== null;
+  }
+
+  delete(key) {
+    this.cache.delete(key);
+  }
+
+  clear() {
+    this.cache.clear();
+  }
+
+  // Invalidate all cache keys matching a pattern
+  invalidatePattern(pattern) {
+    for (const key of this.cache.keys()) {
+      if (key.includes(pattern)) {
+        this.cache.delete(key);
+      }
+    }
+  }
+
+  // Get cache statistics
+  getStats() {
+    return {
+      size: this.cache.size,
+      keys: Array.from(this.cache.keys()),
+    };
+  }
+}
+
+module.exports = new CacheManager();

server/database.js

@@ -100,6 +100,10 @@ try {
   db.prepare("ALTER TABLE resources ADD COLUMN sla_target REAL DEFAULT 99.9").run();
 } catch (err) {}
 
+try {
+  db.prepare("ALTER TABLE resources ADD COLUMN email_to TEXT").run();
+} catch (err) {}
+
 try {
   db.prepare("ALTER TABLE incidents ADD COLUMN acknowledged INTEGER DEFAULT 0").run();
 } catch (err) {}

server/index.js

@@ -7,6 +7,7 @@ const db = require('./database');
 const scheduler = require('./scheduler');
 const monitorService = require('./monitorService');
 const notificationService = require('./notificationService');
+const cache = require('./cache');
 
 const app = express();
 const PORT = process.env.PORT || 3001;
@@ -99,6 +100,10 @@ app.post('/api/resources', (req, res) => {
     email_to || null
   );
 
+  // Invalidate related cache entries
+  cache.invalidatePattern('history:');
+  cache.invalidatePattern('sla:');
+
   res.json({ id: result.lastInsertRowid, message: 'Resource created' });
 });
 
@@ -129,12 +134,22 @@ app.put('/api/resources/:id', (req, res) => {
     email_to || null,
     req.params.id
   );
+
+  // Invalidate related cache entries
+  cache.invalidatePattern('history:');
+  cache.invalidatePattern('sla:');
+
   res.json({ message: 'Resource updated' });
 });
 
 // Delete resource
 app.delete('/api/resources/:id', (req, res) => {
   db.prepare('DELETE FROM resources WHERE id = ?').run(req.params.id);
+  
+  // Invalidate related cache entries
+  cache.invalidatePattern('history:');
+  cache.invalidatePattern('sla:');
+  
   res.json({ message: 'Resource deleted' });
 });
 
@@ -331,6 +346,15 @@ app.get('/api/history/overview', (req, res) => {
   const currentPage = Math.max(1, parseInt(pageParam || page || 1));
   const offset = (currentPage - 1) * pageLimit;
 
+  // Create cache key based on query parameters
+  const cacheKey = `history:days=${days}:page=${currentPage}:limit=${pageLimit}`;
+  
+  // Check cache first
+  const cachedResult = cache.get(cacheKey);
+  if (cachedResult) {
+    return res.json(cachedResult);
+  }
+
   // Get total count of enabled resources
   const totalCount = db.prepare('SELECT COUNT(*) as count FROM resources WHERE enabled = 1').get();
   const total = totalCount.count;
@@ -377,7 +401,12 @@ app.get('/api/history/overview', (req, res) => {
     };
   });
 
-  res.json({ resources: overview, total, page: currentPage, limit: pageLimit });
+  const result = { resources: overview, total, page: currentPage, limit: pageLimit };
+  
+  // Cache result for 2 minutes (120 seconds)
+  cache.set(cacheKey, result, 120);
+  
+  res.json(result);
 });
 
 // Acknowledge incident
@@ -407,6 +436,15 @@ app.get('/api/sla', (req, res) => {
   const currentPage = Math.max(1, parseInt(page));
   const offset = (currentPage - 1) * pageLimit;
 
+  // Create cache key
+  const cacheKey = `sla:days=${days}:page=${currentPage}:limit=${pageLimit}`;
+  
+  // Check cache first
+  const cachedResult = cache.get(cacheKey);
+  if (cachedResult) {
+    return res.json(cachedResult);
+  }
+
   // Get total count
   const totalCount = db.prepare('SELECT COUNT(*) as count FROM resources WHERE enabled = 1').get();
   const total = totalCount.count;
@@ -448,7 +486,12 @@ app.get('/api/sla', (req, res) => {
     };
   });
 
-  res.json({ resources: slaData, total, page: currentPage, limit: pageLimit });
+  const result = { resources: slaData, total, page: currentPage, limit: pageLimit };
+  
+  // Cache result for 3 minutes (180 seconds)
+  cache.set(cacheKey, result, 180);
+  
+  res.json(result);
 });
 
 // Test email

server/notificationService.js

@@ -69,7 +69,8 @@ class NotificationService {
 
     const promises = [];
 
-    if (this.emailEnabled) {
+    // Use resource-specific email if provided, otherwise fall back to global config
+    if (this.emailEnabled && (resource.email_to || this.config.email_to)) {
       promises.push(this.sendEmail(resource, message, incident.type, stats));
     }
 
@@ -141,14 +142,17 @@ class NotificationService {
 
       htmlContent += `</div>`;
 
+      // Use resource-specific email if provided, otherwise use global config
+      const emailTo = resource.email_to || this.config.email_to;
+      
       await this.transporter.sendMail({
         from: this.config.email_from,
-        to: this.config.email_to,
+        to: emailTo,
         subject: `Alert: ${resource.name} is ${type === 'started' ? 'DOWN' : 'UP'}`,
         text: message,
         html: htmlContent,
       });
-      console.log(`Email sent for ${resource.name}`);
+      console.log(`Email sent for ${resource.name} to ${emailTo}`);
     } catch (error) {
       console.error('Email error:', error.message);
     }