🏁 Script executed:

# First, examine the actual file context around lines 68-70
cat -n src/v2.x/packages/runtime/src/endpoints/express-utils.ts | sed -n '60,80p'

Repository: CopilotKit/CopilotKit

Length of output: 856

🏁 Script executed:

# Check for other req.socket usage patterns in the codebase
rg -n 'req\.socket' --type=ts -C2

Repository: CopilotKit/CopilotKit

Length of output: 1058

🏁 Script executed:

# Search for event listener cleanup patterns in the codebase
rg -n '\.removeListener|\.off\(' --type=ts -C2

Repository: CopilotKit/CopilotKit

Length of output: 1567

🏁 Script executed:

# Search for AbortController usage patterns in the codebase
rg -n 'AbortController' --type=ts -C3

Repository: CopilotKit/CopilotKit

Length of output: 9312

🌐 Web query:

Express.js request socket always defined req.socket documentation

💡 Result:

Short answer: req.socket is provided by Node (http.IncomingMessage) and is expected to exist for an active HTTP request — it's the underlying net.Socket for that connection. Historically req.connection was an alias (now deprecated); use req.socket (or req.socket.remoteAddress to get client IP). [1][2]

Sources:

• Node/IncomingMessage socket docs (describes socket as the net.Socket for the request). [1]
• Discussion noting req.connection is deprecated and to use req.socket instead. [2]

🌐 Web query:

Node.js HTTP keep-alive socket persistence multiple requests

💡 Result:

Summary — how Node.js keeps sockets alive and reuses them across multiple requests

• Who manages persistence: the http(s).Agent. It pools sockets per host:port (and TLS options for HTTPS) and hands them to client requests so one TCP connection can serve multiple HTTP/1.1 requests. [1][2]

• Enable it: create an Agent with keepAlive: true (default Agent has keepAlive false). keepAlive keeps sockets in agent.freeSockets after a request completes so they can be reused. Example: new http.Agent({ keepAlive: true }). [1][2]

• Key options:

  • keepAlive (bool) — keep sockets around for reuse. [1]
  • keepAliveMsecs — initial TCP keep-alive probe delay. [1]
  • maxSockets — max concurrent sockets per host before queuing. [1]
  • maxFreeSockets — max idle sockets to keep in the pool. [6]

• When reuse happens: after a request finishes the socket is either returned to freeSockets (if keepAlive true) or destroyed (if false). When a new request for the same agent/host arrives the agent will reuse a free socket if compatible (same host:port:localAddress[:family], and for HTTPS same TLS options). [2][7]

• When reuse fails or ends:

  • Server may close idle connections (agent removes closed sockets). [1]
  • If server refuses multiple requests on the same connection (or response has Connection: close), agent opens a new socket for the next request. [1][4]
  • freeSockets are unref() so they don't keep the Node.js process alive; sockets are also removed on 'timeout' or 'close'. [1][6]

• Best practices:

  • Use a long-lived Agent instance (don’t recreate per request) so connections are reused. [3]
  • Call agent.destroy() when you no longer need it to free OS resources. [2][6]
  • Monitor/adjust maxSockets and maxFreeSockets for your workload and server limits. [1][6]

References
[1] Node.js HTTP docs — Agent options and behavior.
[2] Node.js HTTP docs — agent.keepSocketAlive / reuseSocket / destroy.
[3] AWS Developer Blog — explanation and recommendation to enable keep-alive for SDKs.
[4] StackOverflow discussion — Agent, sockets and request relationships.
[6] Node.js API (freeSockets / timeout behavior).

🌐 Web query:

Node.js event listener cleanup memory leaks socket reuse best practices

💡 Result:

Here are concise best practices for avoiding event-listener memory leaks and safely reusing sockets in Node.js, with sources.

Event-listener cleanup

• Prefer one-time listeners when appropriate: use emitter.once() for short‑lived handlers. [1]
• Always remove handlers you add to emitters you don’t own: emitter.off/removeListener or emitter.removeAllListeners(event) when the handler’s lifetime ends. Keep a reference to the handler so you can remove it. [1][3]
• Avoid adding per-request listeners to long‑lived emitters (or use scoped/temporary emitters). If you must, bound the number of listeners or call remove after use. [3]
• Use emitter.setMaxListeners(n) to surface leaks (MaxListenersExceededWarning) but don’t rely on it to hide real leaks. [1][3]
• Avoid closures that retain large objects in listeners; null out large references when done or use WeakRef/FinalizationRegistry for non‑critical caches/listener state where suitable. [4][3]
• Register 'error' handlers on streams/sockets to avoid unhandled errors keeping state or crashing flows. [1]

Socket/HTTP connection reuse and cleanup

• Use http(s).Agent with keepAlive for socket reuse, tune maxSockets/maxFreeSockets for your workload. Explicitly destroy/close the agent (agent.destroy()) when it will no longer be used to release sockets. [2]
• For long‑running servers, periodically monitor freeSockets/sockets and consider connection timeouts (socket.setTimeout) and proper close/destroy on client disconnects. [2]
• Avoid holding per‑connection large state on the socket object; detach references when the socket ends. [2][3]

Detection and debugging

• Monitor process.memoryUsage(), heap snapshots (Chrome DevTools, heapdump), and use tools like clinic/clinic.js or APMs to find retained objects and listener growth. Watch for MaxListenersExceededWarning and steadily increasing listener counts via emitter.listenerCount(event). [4][3]

Quick code patterns

• Add/remove pattern:
  const handler = (data) => { ... };
  emitter.on('event', handler);
  // later
  emitter.off('event', handler);
  [1]
• Use once:
  emitter.once('event', handler);
  [1]
• Destroy agent when done:
  agent.destroy();
  [2]

Sources
[1] Node.js Events docs (removeListener, once, setMaxListeners, error listener).
[2] Node.js HTTP Agent docs (keepAlive, maxSockets, agent.destroy()).
[3] Articles on Node memory leaks / event emitter leaks (best practices for removing listeners and avoiding leaks).
[4] Guides on debugging leaks (heap snapshots, clinic.js, APM monitoring, WeakRef usage).

If you want, I can: (A) show a short checklist you can paste into code reviews; (B) scan your code (paste a snippet) and point out listener/leak risks.