Page 10 - 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.

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.

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.

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.

Starting Composer and npm from scratch costs minutes on every single build. The good news is that both package managers ship with robust local caches that can persist across Docker builds without inflating the image size. The key lies in correctly separating the lock file layer, the vendor layer and the cache mount, and in understanding which cache type is the right one for each situation.

If you only ever read Docker logs with docker logs, you lose the overview fast in production. Structured logging over stdout and stderr, the right log driver, and a centralized log management system are what make container logs observable, searchable, and alertable.

A slow Magento Docker environment drags down every development cycle. With the right volume strategy, Mutagen sync, correctly configured OPcache, and a running Hyva watcher, perceived speed improves dramatically, without giving up the isolation benefits of Docker.