Scaling Your Application

// Auto-scaling configuration
const scalingConfig = {
  rules: {
    cpu: {
      target: 70,
      min: 2,
      max: 10,
      scaleUp: {
        threshold: 80,
        factor: 2,
        cooldown: 300
      },
      scaleDown: {
        threshold: 40,
        factor: 0.5,
        cooldown: 300
      }
    },
    memory: {
      target: 75,
      min: 2,
      max: 10,
      scaleUp: {
        threshold: 85,
        factor: 2,
        cooldown: 300
      },
      scaleDown: {
        threshold: 50,
        factor: 0.5,
        cooldown: 300
      }
    }
  },

  async evaluate() {
    const metrics = await this.getCurrentMetrics();
    
    for (const [resource, config] of Object.entries(this.rules)) {
      const usage = metrics[resource];
      
      if (usage >= config.scaleUp.threshold) {
        await this.scaleUp(resource, config);
      } else if (usage <= config.scaleDown.threshold) {
        await this.scaleDown(resource, config);
      }
    }
  }
}

// Load balancer configuration
const loadBalancer = {
  algorithm: 'round-robin',
  healthCheck: {
    path: '/health',
    interval: 30,
    timeout: 5,
    unhealthyThreshold: 2,
    healthyThreshold: 3
  },
  
  nodes: [
    {
      host: 'node-1.example.com',
      port: 8080,
      weight: 1
    },
    {
      host: 'node-2.example.com',
      port: 8080,
      weight: 1
    }
  ],

  async route(request) {
    const healthyNodes = await this.getHealthyNodes();
    
    if (healthyNodes.length === 0) {
      throw new Error('No healthy nodes available');
    }
    
    const node = this.selectNode(healthyNodes);
    return this.forwardRequest(request, node);
  },

  async healthCheck() {
    for (const node of this.nodes) {
      try {
        const response = await fetch(`http://${node.host}:${node.port}/health`);
        node.healthy = response.ok;
      } catch (error) {
        node.healthy = false;
      }
    }
  }
}

// Infrastructure scaling
const infrastructure = {
  resources: {
    compute: {
      sizes: {
        small: { cpu: 2, memory: '4GB' },
        medium: { cpu: 4, memory: '8GB' },
        large: { cpu: 8, memory: '16GB' }
      }
    },
    storage: {
      types: ['ssd', 'hdd'],
      sizes: ['50GB', '100GB', '250GB', '500GB']
    }
  },

  async scaleCompute(size) {
    const config = this.resources.compute.sizes[size];
    
    await this.updateNodePool({
      machineType: size,
      nodeCount: this.getCurrentNodeCount(),
      ...config
    });
  },

  async scaleStorage(type, size) {
    await this.updateStorage({
      type,
      size,
      expandOnly: true
    });
  }
}

// Scaling metrics and alerts
const scalingMetrics = {
  async collect() {
    return {
      nodes: await this.getNodeMetrics(),
      scaling: await this.getScalingMetrics(),
      costs: await this.getCostMetrics()
    };
  },

  alerts: {
    nodeCount: {
      warning: {
        min: 2,
        max: 8
      },
      critical: {
        min: 1,
        max: 10
      }
    },
    costs: {
      warning: 1000,
      critical: 1500
    }
  },

  async checkAlerts() {
    const metrics = await this.collect();
    
    if (metrics.nodes.count <= this.alerts.nodeCount.critical.min) {
      await this.sendAlert('critical', 'Insufficient nodes');
    }
    
    if (metrics.costs.monthly >= this.alerts.costs.critical) {
      await this.sendAlert('critical', 'Cost threshold exceeded');
    }
  }
}