Page 20 - Docker

Image signing proves that a container image actually originates from your own pipeline and has not been altered since the build. A software bill of materials lists every single component inside the image and makes supply chain risks visible before they turn into a security incident. Cosign and Syft from the Sigstore ecosystem implement both without requiring your own PKI infrastructure.

A Magento Docker stack consists of at least five services: PHP-FPM, Nginx, MySQL, Redis, and OpenSearch. Add RabbitMQ for message queues and Varnish for full page caching. How these services are correctly networked, persisted, and started in the right order determines stability and maintainability.

An open port does not mean an application is truly ready. Docker Healthchecks give containers a voice of their own: they report when a service can actually process requests, when it is degraded, and when a restart is needed. Without this mechanism, container orchestration stays blind.

Named volumes are the standard way to keep persistent data out of containers, yet without a solid backup strategy they remain a blind spot in operations. Snapshot containers, tar archives and deduplicating tools like restic protect volumes consistently, efficiently and traceably, with retention policies and regular restore tests instead of unverified trust.

An entrypoint script with arrays and process substitution runs fine locally and fails inside an Alpine container with exec format error. The reason is BusyBox ash, which serves as /bin/sh in the default Alpine image instead of Bash and offers only a fraction of the familiar feature set.

Xdebug only works reliably in Docker containers once you understand the three most common pitfalls: incorrect host detection, missing path mapping, and Xdebug overhead during normal operation. Solve these three issues properly once, and debugging in Docker becomes just as comfortable as debugging locally.

The container registry built into GitLab saves you from running an external registry service, but it requires a deliberate tag strategy, automatic cleanup policies against runaway storage usage, and clearly defined access rights per project and group.

Anyone who sets CPU and memory limits for Magento containers by gut feeling either overprovisions expensively or risks outages during traffic spikes. This article shows how Magento container sizes are systematically derived from PHP-FPM pool sizing, real memory demand per worker, and actual traffic patterns, then validated with load tests.

In a classic GitLab pipeline, every stage waits for all jobs of the previous stage to finish, even if a job does not actually depend on the others at all. The needs keyword breaks this rigid order and turns the pipeline into a directed acyclic graph where jobs start as soon as their real dependencies are met, which often shortens overall runtime dramatically.

Once a compose.yaml contains more than three or four services, logging configuration, environment variables and healthcheck definitions repeat almost identically in every block. YAML anchors, aliases and merge keys let you define these blocks once and reuse them everywhere, without Docker Compose needing its own dedicated feature for it.