Senior LevelPHP 8+
How do you architect zero-downtime atomic deployment pipelines for PHP-FPM using symlink switching and OPcache invalidation?
❓ Interview Prompt: Explain zero-downtime PHP deployment pipelines (Deployer/Envoy), timestamped release directories, atomic symlink switching, and OPcache cache invalidation.
Deploying new code by overwriting existing '.php' files in-place causes broken requests, class-not-found errors, and OPcache corruption. Zero-Downtime Atomic Symlink Deployments eliminate this risk.
Pipeline Execution Steps:
1
Release Directory: Deploy new code into a timestamped release folder ('/var/www/releases/20260727120000').
2
Build Phase: Run 'composer install --no-dev', asset compilation, and database migrations in the new release folder.
3
Atomic Symlink Switch: Atomically point the master '/var/www/current' symlink to the new release folder using 'ln -sfn'.
4
OPcache Invalidation: Reload PHP-FPM ('systemctl reload php8.3-fpm') or call 'opcache_reset()' to flush shared memory opcode caches cleanly.
Code Implementation Example
bash
# Zero-Downtime Atomic Symlink Switch & OPcache Reload
ln -sfn /var/www/releases/20260727120000 /var/www/current
# Reload PHP-FPM master process gracefully to flush OPcache without dropping connections!
sudo systemctl reload php8.3-fpm💡Atomic symlink switching and graceful PHP-FPM reload in zero-downtime deployments.
🎯 Interview Key Takeaway
Atomically switch the current symlink to a new release folder and reload PHP-FPM to achieve zero-downtime deployments.
#Zero-Downtime#Deployment#Symlink#OPcache#Senior
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