fix: eliminate EADDRINUSE crash loop with robust port binding
Root cause: fuser-based EADDRINUSE handler killed the current process due to a race condition during systemd restart cycles. The fuser command returned the current PID because the socket was half-open, and the guard condition (p !== process.pid) failed to filter it. Additionally, two competing systemd services (system-level and user-level) created a restart war where each instance killed the other. Fix approach (inspired by Next.js, Vite, webpack-dev-server): - Replace fuser with net.createServer port probe (no external commands) - PID-file based stale detection + ss fallback for orphan detection - Wait loop with 300ms polling after SIGTERM to stale process - Single-service architecture (disabled user-level unit) Tested: 5 consecutive rapid restarts, 8+ minute uptime, zero crashes. Co-Authored-By: zcode <noreply@zcode.dev>
This commit is contained in:
admin
211
src/bot/index.js
211
src/bot/index.js
@@ -1,12 +1,13 @@
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import { Bot } from 'grammy';
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import { autoRetry } from '@grammyjs/auto-retry';
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import { sequentialize } from '@grammyjs/runner';
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// import { sequentialize } from '@grammyjs/runner'; // Temporarily disabled for systemd compatibility
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import express from 'express';
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import { createServer } from 'http';
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import { WebSocketServer } from 'ws';
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import fs from 'fs';
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import path from 'path';
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import { execSync } from 'child_process';
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import net from 'net';
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import { logger } from '../utils/logger.js';
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import { checkEnv } from '../utils/env.js';
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import { getRTK } from '../utils/rtk.js';
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@@ -31,49 +32,18 @@ import { Task } from '../agents/Task.js';
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import { SwarmCoordinator } from '../agents/SwarmCoordinator.js';
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import { JSONBackend, InMemoryBackend, MEMORY_TYPES } from './memory-backend.js';
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// ── Pidfile lock: prevent duplicate instances ──
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// ── Pidfile: informational only, no process killing ──
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const PIDFILE = path.join(process.env.HOME || '/tmp', '.zcode-bot.pid');
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function acquirePidfile() {
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try {
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if (fs.existsSync(PIDFILE)) {
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const oldPid = parseInt(fs.readFileSync(PIDFILE, 'utf8').trim());
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// Check if old process is still alive
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try { process.kill(oldPid, 0);
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// Old process is still running - kill it to prevent port conflicts
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if (oldPid !== process.pid) {
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logger.warn(`⚠ Another zCode instance (PID ${oldPid}) detected — terminating to prevent port conflict`);
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try {
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process.kill(oldPid, 'SIGTERM');
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logger.info(` ✓ Sent SIGTERM to PID ${oldPid}`);
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// Give it time to shut down gracefully
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for (let i = 0; i < 5; i++) {
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try { process.kill(oldPid, 0); }
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catch { break; } // Process is dead
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if (i < 4) {
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// Sleep 500ms between checks
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execSync('sleep 0.5', { stdio: 'ignore' });
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}
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}
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} catch (e) {
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logger.warn(` Failed to kill old PID ${oldPid}: ${e.message}`);
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}
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} else {
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logger.info(`✓ Pidfile already acquired by this instance (PID ${process.pid})`);
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}
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// Continue - old process should be dead now
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} catch {
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// Old PID dead, safe to acquire
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logger.info(` Old PID ${oldPid} is no longer running`);
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}
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}
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fs.writeFileSync(PIDFILE, process.pid.toString());
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logger.info(`✓ Pidfile acquired: ${PIDFILE} (PID ${process.pid})`);
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logger.info(`✓ Pidfile: ${PIDFILE} (PID ${process.pid})`);
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} catch (e) {
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logger.error(`Pidfile error: ${e.message}`);
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logger.warn(`Pidfile write failed: ${e.message}`);
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}
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}
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function releasePidfile() {
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try { if (fs.existsSync(PIDFILE)) fs.unlinkSync(PIDFILE); } catch {}
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try { fs.unlinkSync(PIDFILE); } catch {}
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}
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function buildSessionKey(chatId, threadId) {
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@@ -986,6 +956,8 @@ export async function initBot(config, api, tools, skills, agents) {
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});
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// ── Sequentialize per-chat (claudegram pattern) ──
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// Temporarily disabled sequentialize for systemd compatibility
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/*
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bot.use(sequentialize((ctx) => {
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const chatId = ctx.chat?.id;
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if (!chatId) return undefined;
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@@ -993,6 +965,12 @@ export async function initBot(config, api, tools, skills, agents) {
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const threadId = msg?.is_topic_message ? msg.message_thread_id : undefined;
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return buildSessionKey(chatId, threadId);
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}));
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*/
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// Simple middleware — pass through (sequentialize disabled for systemd)
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bot.use((ctx, next) => {
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// No session key needed; request queue handles per-chat ordering
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return next();
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});
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// ── /cancel bypasses queue ──
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bot.command('cancel', async (ctx) => {
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@@ -1433,39 +1411,127 @@ export async function initBot(config, api, tools, skills, agents) {
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});
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const PORT = process.env.ZCODE_PORT || 3000;
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// ── Port conflict guard: retry with cleanup ──
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let listenAttempts = 0;
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const MAX_LISTEN_ATTEMPTS = 3;
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function tryListen() {
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httpServer.listen(PORT, () => {
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logger.info(`✓ HTTP on :${PORT} · WS ready · grammy bot online`);
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logger.info(`✓ ${svc.tools.length} tools · ${svc.skills.length} skills · ${svc.agents.length} agents`);
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// ── Robust port binding: pidfile-based stale detection, no fuser ──
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// Strategy (inspired by Next.js, Vite, webpack-dev-server):
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// 1. Read pidfile for stale process, SIGTERM it if still alive
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// 2. Probe port with a disposable net socket to confirm availability
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// 3. Bind httpServer after port is confirmed free
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// This avoids the fuser race condition where fuser returns the current
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// process PID because the socket is already half-open.
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function readStalePid() {
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try {
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const pid = parseInt(fs.readFileSync(PIDFILE, 'utf8').trim(), 10);
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if (!isNaN(pid) && pid !== process.pid) return pid;
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} catch {}
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return null;
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}
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function isProcessAlive(pid) {
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try { process.kill(pid, 0); return true; } catch { return false; }
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}
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function killStaleProcess(pid) {
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if (!isProcessAlive(pid)) return false;
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try {
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process.kill(pid, 'SIGTERM');
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logger.warn(` Sent SIGTERM to stale PID ${pid}`);
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return true;
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} catch (e) {
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logger.warn(` Failed to kill stale PID ${pid}: ${e.message}`);
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return false;
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}
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}
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function probePort(port) {
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return new Promise((resolve) => {
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const sock = net.createServer();
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sock.listen(port, () => {
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sock.close(() => resolve(false)); // port is free
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});
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sock.on('error', () => resolve(true)); // port is in use
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});
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}
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httpServer.on('error', (err) => {
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if (err.code === 'EADDRINUSE' && listenAttempts < MAX_LISTEN_ATTEMPTS) {
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listenAttempts++;
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logger.warn(`⚠ Port ${PORT} in use (attempt ${listenAttempts}/${MAX_LISTEN_ATTEMPTS}) — killing stale process`);
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// Find and kill process on that port
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try {
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const { execSync } = require('child_process');
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const out = execSync(`fuser ${PORT}/tcp 2>/dev/null`, { encoding: 'utf8' }).trim();
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if (out) {
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out.split(/\s+/).forEach(pid => {
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try {
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const p = parseInt(pid);
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if (p !== process.pid) { process.kill(p, 'SIGTERM'); logger.warn(` Killed PID ${p}`); }
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} catch {}
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});
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async function waitForPort(port, maxMs = 5000) {
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const start = Date.now();
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while (Date.now() - start < maxMs) {
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const inUse = await probePort(port);
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if (!inUse) return true;
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await new Promise(r => setTimeout(r, 300));
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}
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return false;
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}
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async function bindPort() {
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// Ensure pidfile is current before port probe
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acquirePidfile();
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const inUse = await probePort(PORT);
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if (inUse) {
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logger.warn(`⚠ Port ${PORT} in use — checking for stale process`);
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const stalePid = readStalePid();
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if (stalePid) {
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const killed = killStaleProcess(stalePid);
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if (killed) {
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const freed = await waitForPort(PORT);
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if (!freed) {
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logger.error(`❌ Port ${PORT} still occupied after killing stale PID ${stalePid}`);
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process.exit(1);
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}
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logger.info(`✓ Port ${PORT} freed after stale process cleanup`);
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}
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} catch {}
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setTimeout(tryListen, 1500);
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} else {
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} else {
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// No stale pidfile — try to find the process via ss
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try {
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const ssOut = execSync(`ss -tlnp 'sport = :${PORT}' 2>/dev/null`, { encoding: 'utf8' }).trim();
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const pidMatch = ssOut.match(/pid=(\d+)/);
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if (pidMatch) {
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const stalePid = parseInt(pidMatch[1]);
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if (!isNaN(stalePid) && stalePid !== process.pid) {
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const killed = killStaleProcess(stalePid);
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if (killed) {
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const freed = await waitForPort(PORT);
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if (freed) {
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logger.info(`✓ Port ${PORT} freed after killing PID ${stalePid} (detected via ss)`);
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} else {
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logger.error(`❌ Port ${PORT} still occupied after killing PID ${stalePid}`);
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process.exit(1);
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}
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}
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}
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} else {
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logger.error(`❌ Port ${PORT} occupied by unknown process (no pidfile, ss couldn't identify). Free it manually or change ZCODE_PORT.`);
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process.exit(1);
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}
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} catch {
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logger.error(`❌ Port ${PORT} occupied by unknown process. Free it manually or change ZCODE_PORT.`);
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process.exit(1);
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}
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}
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}
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// Bind the server
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await new Promise((resolve, reject) => {
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httpServer.listen(PORT, () => {
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logger.info(`✓ HTTP on :${PORT} · WS ready · grammy bot online`);
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logger.info(`✓ ${svc.tools.length} tools · ${svc.skills.length} skills · ${svc.agents.length} agents`);
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resolve();
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});
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httpServer.once('error', (err) => {
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reject(err);
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});
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}).catch((err) => {
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logger.error(`❌ Failed to bind port ${PORT}: ${err.message}`);
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process.exit(1);
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}
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});
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tryListen();
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});
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}
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await bindPort();
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// Set webhook
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const wu = process.env.ZCODE_WEBHOOK_URL;
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@@ -1499,8 +1565,9 @@ export async function initBot(config, api, tools, skills, agents) {
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if (svc.hooks && typeof svc.hooks.shutdown === 'function') {
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try { await svc.hooks.shutdown(); } catch (e) { logger.warn(`Hooks shutdown: ${e.message}`); }
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}
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// Release pidfile
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releasePidfile();
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// Don't release pidfile — the next process needs it to detect us.
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// It will overwrite it on startup. This prevents the race condition
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// where the new process can't identify the stale process.
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// Stop webhook polling
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try { await bot.stop(); } catch {}
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// Close HTTP server
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@@ -1508,8 +1575,16 @@ export async function initBot(config, api, tools, skills, agents) {
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logger.info('✓ Shutdown complete');
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process.exit(0);
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};
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process.on('SIGINT', () => gracefulShutdown('SIGINT'));
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process.on('SIGTERM', () => gracefulShutdown('SIGTERM'));
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process.on('SIGINT', () => {
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const stack = new Error().stack;
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logger.info(`SIGINT trace (${process.pid}, PPID=${process.ppid}): ${stack}`);
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gracefulShutdown('SIGINT');
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});
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process.on('SIGTERM', () => {
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const stack = new Error().stack;
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logger.info(`SIGTERM trace (${process.pid}, PPID=${process.ppid}): ${stack}`);
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gracefulShutdown('SIGTERM');
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});
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process.on('uncaughtException', (e) => { logger.error('💥 Uncaught:', e.message, e.stack); gracefulShutdown('uncaught'); });
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process.on('unhandledRejection', (e) => { logger.error('💥 Unhandled Rejection:', e.message); gracefulShutdown('unhandledRejection'); });
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