Page 4 - Docker

Running DI compile and static content deploy at runtime slows down every deployment and risks inconsistent images. The build container approach moves both steps into image creation, giving you reproducible results and much faster release cycles.

The most common mistake in multi-service Docker stacks: an application starts and tries to connect to the database before it is ready. depends_on without a condition only resolves the start order of the containers, not the readiness of the service behind them. This article covers every pattern that solves the problem reliably: from health-check-based dependencies through wait-for-it to robust application-side retry logic.

Anyone running local development environments with Docker Compose knows the problem: a bind mount mirrors everything, but node_modules, vendor directories and build artifacts cause performance issues and conflicts between host and container. Docker Compose Watch solves this precisely with three actions, sync, rebuild and sync and restart, finally making live reload predictable.

Anyone running multiple Magento stores for different clients or brands faces the question of whether every shop needs its own Compose stack, or whether one shared stack with clearly separated networks, database schemas and caches is enough. This article shows how a single Docker Compose stack reliably isolates multiple Magento stores without duplicating resources for every shop.

Anyone watching container metrics only through docker stats loses history and alerting capability. cAdvisor reads CPU, memory, network and I/O for every container, Prometheus stores the time series permanently, and PromQL turns them into reliable figures for capacity planning and troubleshooting in live operations.

A devcontainer moves the entire development environment into a container, so every developer uses the exact same PHP version, the same extensions and the same tools, regardless of their own machine. Instead of hours of onboarding documentation, a single click on "Reopen in Container" is enough.

Service discovery is the invisible backbone of every Docker Swarm cluster: internal DNS, virtual IP addresses and a cluster wide routing mesh make sure containers reach each other through stable names, even though the actual placement can change at any time. Understanding these mechanisms lets you resolve networking problems in Swarm much faster.

Reproducible Docker builds produce the same image digest from identical source code and identical configuration on every build, no matter when or on which machine the build ran. SOURCE_DATE_EPOCH eliminates the biggest source of noise behind non-determinism, the current timestamp embedded into every layer.

An open database port does not mean MySQL is ready to process connections. depends_on with condition service_healthy ties the startup order of Docker Compose services directly to the healthcheck status, instead of relying on a plain reachability signal, and eliminates one of the most common sources of errors in multi service stacks.

An ephemeral review app is automatically created as soon as a pull request is opened, and disappears without a trace once it is merged or closed. Docker Compose builds a dedicated, isolated stack per branch for this, reachable through a dynamic subdomain, with no manual environment management at all.