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🚀 Zero Downtime (ZDT) Deployment for PHP

Keeping applications always available is essential. During the update process (redeploy), many services face errors or become unavailable. The SaveinCloud platform offers a simple and efficient method to solve this problem in PHP applications: ZDT Deployment, based on best practices adopted by large companies like Etsy.

🔧 How it works​

The ZDT Deployment process is based on two pillars:

  1. With each new deployment, the application files are copied to a new folder with a timestamp.

  2. A symlink (symbolic link) points to the current version of the application and is redirected instantly at the end of the deployment.

This allows:

  • The old version to continue serving users during the process.

  • The new version to be activated atomically at the end.

  • No interruption in the service.

📈 Deployment Flow​

1. Create or use an existing PHP environment​

It is recommended to use Apache (with support for the mod_realdoc module) or NGINX.

2. Enable ZDT when deploying​

When deploying a .zip or direct link:

  • Check the option "Enable zero-downtime deployment" imagem

Or, when using a Git/SVN/Bitbucket repository: imagem

  • The option is automatically enabled when deploying in the ROOT context.

⚠️ This option only works if the deployment is done in the ROOT context.

3. Directory structure​

With each deployment:

  • A new folder is created like ROOT_yyyy.mm.dd-hh.mm.ss

  • The symlink ROOT points to the active version


ls  -l  /var/www/webroot

imagem

4. Future updates​

With each new deployment:

  • A new folder is created

  • The symlink is updated automatically

  • The previous version is kept (you can delete it manually later)

⚙️ Technical implementation

Apache PHP​

Uses the mod_realdoc module with configurations in:


/etc/httpd/conf.d/mod_realdoc.conf

Useful parameter: RealpathEvery 2

NGINX PHP​

Native support for ZDT, with adjustments at the end of the file:


/etc/nginx/nginx.conf

⚖️ Comparison between methods​

MethodResponse TimeFailuresAvailability
Classic DeployFasterHasThere is downtime
ZDT DeploySlightly higherNoneAlways online ✅

📊 Tests with WordPress​

Deploy via File (Classic)​

  • Failure time: up to 2 seconds

  • Errors during the process

Deploy via File (ZDT)​

  • No errors

  • Instant version switch

Deploy via Git (Classic)​

  • May fail during clone/push

Deploy via Git (ZDT)​

  • Stable, no downtime

  • Preserves user-generated files

✅ Benefits​

  • Smooth and transparent update

  • Preserves user-generated content

  • Lower risk of errors and downtime

🔚 Conclusion​

ZDT Deployment is the best way to update PHP applications without impacting your users. With it, you ensure stability, security, and efficiency in your project update process.

💡 Recommended for all PHP environments with continuous or frequent deployment.