Wordpress Stuck/hang/inresponsive/504/timeout/CPU

gistfile1.txt

If you're seeing 100% CPU usage and `504 Gateway Timeout` errors from NGINX, but you've disabled plugins and the issue persists, you're likely dealing with a **lower-level issue** in WordPress or the server environment. Here's how to **debug this methodically and critically**:

---

## 🔍 1. **Check What Is Actually Using CPU**

Run the following command on the server to identify what's consuming CPU:

```bash
top -o %CPU
```

Or for a more readable breakdown:

```bash
htop
```

Look for:

* Is it `php-fpm`, `mysql`, or some rogue process?
* Are there many worker processes?
* Are multiple cores maxed, or just one?

---

## 🔧 2. **PHP-FPM Tuning / Bottleneck**

If `php-fpm` is the top CPU consumer:

### Check the pool config:

```bash
cat /etc/php/*/fpm/pool.d/www.conf
```

Things to review:

```ini
pm = dynamic
pm.max_children = 50
pm.start_servers = 5
pm.min_spare_servers = 5
pm.max_spare_servers = 35
```

If `pm.max_children` is too low, requests queue and time out.
If too high, server swaps → CPU spikes.

---

## 🧠 3. **Run strace on High-CPU Processes**

To inspect what a high-CPU process is doing:

```bash
sudo strace -p <PID>
```

You'll see if it's waiting on I/O, stuck in loops, calling specific PHP files, etc.

---

## 🔎 4. **Find the Entry Point of the Problem**

If it’s `php-fpm`:

```bash
sudo lsof -p <php-fpm-pid>
```

See what file is being processed. Could be a heavy page or loop.

Also, log slow PHP scripts:
In `php.ini` or `www.conf`:

```ini
request_slowlog_timeout = 3s
slowlog = /var/log/php-fpm.slow.log
```

---

## 🔄 5. **Check MySQL / MariaDB Queries**

If it's `mysqld` using CPU, run:

```sql
SHOW PROCESSLIST;
```

or from CLI:

```bash
mysqladmin processlist
```

Look for long-running or locked queries.

Also useful:

```sql
SHOW ENGINE INNODB STATUS\G;
```

If CPU is high due to `mysql`, it could be:

* A bad plugin leaving a query open
* A WooCommerce table like `wp_options` bloated
* Autoloaded options

Check this:

```sql
SELECT COUNT(*) FROM wp_options WHERE autoload = 'yes';
SELECT SUM(LENGTH(option_value)) AS autoload_size FROM wp_options WHERE autoload = 'yes';
```

> Should ideally be < 1MB in size. If it's >10MB, this can cripple performance.

---

## 📉 6. **Check NGINX and PHP Logs**

* NGINX error logs:

  ```bash
  /var/log/nginx/error.log
  ```
* PHP error log (often in `/var/log/php*`)
* Check for:

  * Upstream timeouts
  * Script errors
  * Socket errors (`upstream: "fastcgi://unix:/run/php/php7.x-fpm.sock"`)

---

## 🔥 7. **Disable Themes + Core Check**

Since you disabled plugins, try **switching to a default theme** (`twentytwentyfour`) to rule out theme issues:

```php
define('WP_USE_THEMES', false);
```

Or via DB:

```sql
UPDATE wp_options SET option_value = 'twentytwentyfour' WHERE option_name = 'template' OR option_name = 'stylesheet';
```

Also try:

```php
define('WP_DISABLE_FATAL_ERROR_HANDLER', true);
define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
```

---

## 🧰 8. **Run WordPress Through CLI**

Try using `wp-cli` to run:

```bash
wp cron event list
wp option list --autoload --format=csv > autoload.csv
```

And check for stuck cron jobs or huge autoloaded options.

---

## 🧪 9. **Profiling with Xdebug or Tideways**

If you still can’t isolate the cause, install a PHP profiler:

* [`xdebug`](https://xdebug.org/docs/profiler)
* [`tideways`](https://tideways.com/profiler)

This gives you exact lines of PHP code causing high CPU.

---

## 🛡️ 10. **Other Considerations**

* DoS? Check NGINX access logs for sudden surges:

  ```bash
  tail -n 1000 /var/log/nginx/access.log | awk '{print $1}' | sort | uniq -c | sort -nr | head
  ```

* Malware? Run:

  ```bash
  clamscan -r /var/www/html
  ```

---

## Next Step

If you want, you can upload the output of:

```bash
top -b -n 1
```

and your:

* `/etc/php/*/fpm/pool.d/www.conf`
* MySQL processlist
* Last 100 lines of `access.log` and `error.log`

I'll help you pinpoint the bottleneck exactly.

---

Would you like help writing a short script to log CPU usage and top 5 PHP scripts in real-time?