Fix crash loop: disable keep-alive agents and add unhandledRejection guard

The previous fix (agent .on('error')) doesn't reach individual socket
objects — socket-level parse errors still escaped as uncaught exceptions.

Root fix: disable keepAlive on the HTTP/HTTPS monitoring agents. Without
connection reuse there is no stale connection to trigger "Parse Error:
Data after Connection: close". Monitoring intervals are 60s+ so the lack
of connection pooling has no meaningful performance impact.

Belt-and-suspenders: add process.on('unhandledRejection') alongside the
existing uncaughtException guard to catch any async paths that leak.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013AQYLFrscmMnzMiXAAANoa

server/index.js

@@ -6,8 +6,8 @@ const http = require('http');
 const { randomUUID } = require('crypto');
 require('dotenv').config();
 
-// Prevent HTTP parser errors (e.g. from keep-alive connections to monitored
+// Prevent HTTP parser errors (e.g. "Data after Connection: close") and other
-// services that send data after Connection: close) from crashing the process.
+// transient async errors from crashing the process.
 process.on('uncaughtException', (err) => {
   if (err.code === 'HPE_INVALID_CONSTANT' || (err.message && err.message.includes('Parse Error'))) {
     console.error('HTTP parse error (swallowed):', err.message);
@@ -17,6 +17,15 @@ process.on('uncaughtException', (err) => {
   process.exit(1);
 });
 
+process.on('unhandledRejection', (reason) => {
+  const msg = reason instanceof Error ? reason.message : String(reason);
+  if (msg.includes('Parse Error')) {
+    console.error('HTTP parse error (swallowed):', msg);
+    return;
+  }
+  console.error('Unhandled rejection:', reason);
+});
+
 const db = require('./database');
 const scheduler = require('./scheduler');
 const monitorService = require('./monitorService');

server/monitorService.js

@@ -31,14 +31,14 @@ function parseHostPort(urlString, fallbackPort) {
 
 class MonitorService {
   constructor() {
-    // Keep-alive agents for pooled HTTP/S connections.
+    // Disable keep-alive to avoid "Parse Error: Data after Connection: close"
-    // Socket-level 'error' listener prevents parse errors (e.g. "Data after
+    // crashes. Keep-alive connection reuse causes the HTTP parser to throw
-    // Connection: close") from bubbling up as uncaught exceptions when a
+    // when a monitored server sends extra data after Connection: close — the
-    // monitored server sends a malformed response on a reused connection.
+    // socket-level error becomes an uncaught exception that kills the process.
-    this.httpAgent = new http.Agent({ keepAlive: true, maxSockets: 50 });
+    // Monitoring checks are infrequent enough that connection pooling provides
-    this.httpAgent.on('error', () => {});
+    // no meaningful benefit.
-    this.httpsAgent = new https.Agent({ keepAlive: true, maxSockets: 50 });
+    this.httpAgent = new http.Agent({ keepAlive: false });
-    this.httpsAgent.on('error', () => {});
+    this.httpsAgent = new https.Agent({ keepAlive: false });
     
     // Circuit breaker for HTTP checks (5 failures before opening, 60s reset)
     this.httpCircuitBreaker = new CircuitBreaker(5, 60000, this.isTransientError);