Intermediate

Compose excels at local development. Production usually runs on Kubernetes. Maintaining two parallel descriptions of the same application is where drift, bugs, and “works on my laptop” stories come from. Compose Bridge bridges that gap by turning a Compose file into a deployable Kubernetes artifact, without asking you to maintain a second source of truth. This is the first part of a three-post deep dive on Compose Bridge. Part 1 covers what it is and how it works. Part 2 goes into custom transformers and enterprise customization. Part 3 shows how to deploy an AI application with Docker Model Runner to Kubernetes. ...

docker compose up --wait (Tip #51) waits for services to become healthy. docker compose wait does something different: it waits for services to exit, and returns their exit code. Basic usage docker compose wait <service> The command blocks until the specified service stops, then prints the exit code. If you echo $? after, it’s the same value. This is perfect for one-shot services: migrations, batch jobs, test runners, anything that runs and exits. ...

By default, Compose pulls an image when it’s missing locally and uses the cached one otherwise. pull_policy lets you change that behavior per service. The policies services: web: image: nginx pull_policy: always Available values: missing (default when no build: is defined): pull only if the image is not present locally. Alias: if_not_present. Note: the latest tag is always pulled even with this policy. always: pull on every up, even if the local image is recent never: don’t pull, fail if the image is missing build: build the image, rebuilds even if it’s already present locally daily: check the registry if the last pull was more than 24 hours ago weekly: check the registry if the last pull was more than 7 days ago every_<duration>: check the registry if the last pull was older than the given duration. Units: w, d, h, m, s (or any combination, e.g. every_12h, every_30m, every_1d12h) When to use each always for development against a fast-moving tag: ...

Compose volumes default to local disk on the host running the container. When you need storage shared across hosts, a volume driver does the job. The built-in local driver already supports NFS through its options. Basic NFS mount Declare a volume that points to an NFS export: volumes: shared: driver: local driver_opts: type: nfs o: "addr=nfs-server.example.com,rw,nfsvers=4" device: ":/exports/shared" services: app: image: myapp volumes: - shared:/data The app service mounts /exports/shared from the NFS server at /data inside the container. Multiple containers (or even multiple Compose stacks on different hosts) can mount the same volume to share data. ...

By default, containers inherit DNS configuration from the Docker daemon. When you need to override that, three directives give you full control: dns:, dns_search:, and dns_opt:. Setting custom DNS servers dns: overrides which resolvers the container queries: services: app: image: myapp dns: - 1.1.1.1 - 8.8.8.8 The container now uses Cloudflare and Google DNS instead of whatever the host provides. Useful when: The host DNS is slow or unreliable for your use case You need a specific public DNS for content filtering (Pi-hole, NextDNS) A development environment must reach internal services through a corporate DNS server Search domains dns_search: adds search domains so short names resolve against them: ...