Service links

A service link describes how one service connects to another service.

One common example is an Nginx link to its upstream backend such as PHP-FPM.

Some links are mandatory and some are optional. If a link is mandatory, the stack must specify which other service satisfies it.

For example, in a Drupal stack the PHP service may require a Database link. That link can point either to a container-based MariaDB service or to an external cloud database service.

Service links are defined under the links section in a service template.

Links also affect deployment ordering. When two linked app services are included in the same deployment, Wodby deploys the linked target service first and then deploys the service that depends on it.

This ordering follows the current app-service links for that app instance, not only the original stack defaults. In practice, changing a link at the app level can also change the deployment order for future deployments of that instance.