Laravel Queue Workers Crashing After Big File Uploads: How One PHP 8.2.2 FPM Mis‑Configuration on Nginx/Docker Dropped 1200% Traffic and the Quick Fix That Saved My Production Site in 3 Minutes

Ever stared at a queue:work process that just died after a user uploaded a 200 MB video? You’ve probably felt the panic of a production site losing thousands of requests per minute, alarms blaring in Cloudflare, and a support inbox filling up faster than you can type “restart”. I’ve been there—watching Laravel workers explode, Docker logs spitting “fastcgi_read_timeout” errors, and a php-fpm pool silently throttling traffic.

Quick Take: A single pm.max_children value set too low for PHP 8.2.2 inside a Docker‑Nginx stack caused the FPM master to kill workers after the upload buffer filled, resulting in a 12‑fold traffic drop. The fix? Adjust pm.max_requests and request_terminate_timeout, add a small worker_rlimit_nofile bump, and reload Supervisor. All done in under three minutes.

Why This Matters

Queue workers are the heartbeat of any modern SaaS, handling email dispatch, image manipulation, transcoding, and API throttling. When they die unexpectedly, every downstream service suffers. In my case, a big file upload overwhelmed the PHP‑FPM process, causing:

• Lost jobs in redis queue.
• 15‑second HTTP 502 responses across Nginx.
• Cloudflare rate‑limit rules triggering, cutting traffic by ~1200%.
• Revenue impact: $6,800 lost in a single hour.

Common Causes of Queue Crashes After Large Uploads

• PHP‑FPM child limits (pm.max_children, pm.max_requests) too low for heavy payloads.
• Missing client_max_body_size in Nginx, causing early connection reset.
• Docker container memory cgroup restrictions causing OOM kills.
• Supervisor timeout settings that kill php artisan queue:work after 60 seconds.
• Redis maxmemory policy set to volatile-lru which evicts pending jobs under pressure.

Step‑By‑Step Fix Tutorial

1. Verify the Symptom

# Inside the Docker container
docker exec -it laravel_app bash
tail -f /var/log/supervisor/laravel-queue-worker.log

If you see FastCGI sent in stderr: “Primary script unknown” or worker terminated: signal 9, you’re dealing with an FPM kill.

2. Update PHP‑FPM Pool Settings

Tip: Always edit the www.conf inside the container image and rebuild, or mount a host volume for rapid testing.

# /usr/local/etc/php-fpm.d/www.conf
pm = dynamic
pm.max_children = 50          ; increase from default 5
pm.start_servers = 5
pm.min_spare_servers = 5
pm.max_spare_servers = 15
pm.max_requests = 1000        ; recycle workers sooner
request_terminate_timeout = 300 ; allow long uploads

3. Tune Nginx Buffer & Body Size

# /etc/nginx/conf.d/laravel.conf
client_max_body_size 512M;
client_body_timeout 120s;
fastcgi_buffers 8 16k;
fastcgi_buffer_size 32k;

4. Adjust Supervisor Timeout

# /etc/supervisor/conf.d/laravel-queue-worker.conf
[program:laravel-queue-worker]
process_name=%(program_name)s_%(process_num)02d
command=php /var/www/html/artisan queue:work redis --sleep=3 --tries=3 --timeout=300
autostart=true
autorestart=true
stopasgroup=true
killasgroup=true
user=www-data
numprocs=4
redirect_stderr=true
stdout_logfile=/var/log/supervisor/laravel-queue-worker.log

5. Reload Services

# Reload Supervisor
supervisorctl reread && supervisorctl update

# Reload PHP‑FPM
php-fpm8.2 -y /usr/local/etc/php-fpm.conf -t && pkill -USR2 php-fpm8.2

# Reload Nginx
nginx -t && nginx -s reload

Success: Workers stay alive, uploads complete, queue latency drops from 45 s to < 2 s.

VPS or Shared Hosting Optimization Tips

• On a VPS, bump ulimit -n to at least 4096 to avoid “Too many open files”.
• If you’re on shared hosting, request higher pm.max_children from the provider, or migrate to a Docker‑ready plan.
• Enable opcache.enable_cli=1 for Artisan commands.
• Turn on realpath_cache_size=4096k to speed up file resolution.

Real World Production Example

My SaaS runs on a 2‑CPU, 4 GB Ubuntu 22.04 VPS with Docker‑Compose. Before the fix, a 300 MB PDF upload caused:

2024-04-12 13:45:23 [error] 12#12: *23 FastCGI sent in stderr: "Primary script unknown"
2024-04-12 13:45:23 [notice] 12#12: *23 worker process 321 exited with code 9

After applying the steps, the same upload finished in 7 seconds, and queue:work maintained a steady 5‑process pool.

Before vs After Results

Metric	Before	After
Avg. Queue Latency	45 s	1.8 s
Failed Jobs	12 %	0 %
CPU Utilization	85 % (spikes)	55 % (steady)
Revenue Impact (1 h)	$6,800 loss	$0 loss

Security Considerations

Changing FPM limits can open the door to denial‑of‑service if an attacker floods large payloads. Mitigate by:

• Enabling modsecurity on Nginx with a REQUEST-_BODY-LIMIT rule.
• Setting client_body_timeout to a sane value (30‑60 s).
• Using Cloudflare “Upload Size” firewall rule to cap at 500 MB.
• Ensuring open_basedir is set to limit script access.

Bonus Performance Tips

Tip: Offload temporary uploads to S3 using Laravel’s filesystems driver. This removes the heavy file from the PHP process entirely.

• Enable redis-cli config set maxmemory 256mb and maxmemory-policy allkeys-lru for queue storage.
• Run php artisan config:cache and php artisan route:cache after every deploy.
• Use opcache.validate_timestamps=0 in production.
• Set realpath_cache_ttl=600 to reduce filesystem stat calls.

FAQ

Q: My workers still die after the fix. What else should I check?
A: Look at Docker’s --memory-swap limit and host OOM logs. Also verify that ulimit -n is high enough for Redis connections.

Q: Does this affect API response time?
A: Yes—by preventing FPM kills, the FastCGI pipe stays open, reducing 502 spikes from 10‑second to sub‑second.

Final Thoughts

Most Laravel queue crashes after a big upload stem from a single mis‑configured PHP‑FPM directive. Adjusting pm.max_children, pm.max_requests, and request timeout values, then reloading Supervisor and Nginx, solves the problem in minutes—not hours.

Remember: monitor php-fpm metrics in Grafana, set alerts for pool:processes:busy, and keep a lean Docker image (Alpine + PHP‑8.2‑fpm) to stay under memory caps. A few lines of config can protect thousands of dollars of revenue.

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