fix: don't blow up if you reach max integer requests

Author: joeyguerra

lib/LoadBalancer.mjs

@@ -36,6 +36,11 @@ export default class LoadBalancer {
   selectRoundRobin(instances) {
     if (instances.length === 0) return null
 
+    // Reset counter if approaching MAX_SAFE_INTEGER to prevent overflow
+    if (this.roundRobinIndex >= Number.MAX_SAFE_INTEGER - 1) {
+      this.roundRobinIndex = 0
+    }
+    
     const selectedInstance = instances[this.roundRobinIndex % instances.length]
     this.roundRobinIndex = (this.roundRobinIndex + 1) % instances.length
 

test/LoadBalancer.test.mjs

@@ -79,6 +79,28 @@ describe('LoadBalancer', () => {
         assert.strictEqual(instance.instanceId, 'client-1')
       }
     })
+
+    test('should reset counter when approaching MAX_SAFE_INTEGER', () => {
+      const instances = [
+        { instanceId: 'client-1' },
+        { instanceId: 'client-2' },
+        { instanceId: 'client-3' }
+      ]
+      
+      // Set counter close to MAX_SAFE_INTEGER
+      loadBalancer.roundRobinIndex = Number.MAX_SAFE_INTEGER - 1
+      
+      // Should reset and continue normally
+      const instance = loadBalancer.selectRoundRobin(instances)
+      assert(instance)
+      assert.strictEqual(instance.instanceId, 'client-1') // Starts from beginning after reset
+      assert.strictEqual(loadBalancer.roundRobinIndex, 1) // Incremented to 1 after selecting index 0
+      
+      // Next call should work normally
+      const nextInstance = loadBalancer.selectRoundRobin(instances)
+      assert.strictEqual(nextInstance.instanceId, 'client-2')
+      assert.strictEqual(loadBalancer.roundRobinIndex, 2)
+    })
   })
 
   describe('selectRandom', () => {