Docker Engine 17.03: What's New, Release History & EOL Status

What Is New in Docker Engine 17.03

Docker Engine 17.03.0-ce is the inaugural release of the new monthly-based release cycle, focusing on smaller, more frequent updates. This version delivers key enhancements in multi-stage builds, orchestration, and networking.

How do multi-stage builds change Dockerfile creation?

Multi-stage builds are a complete game-changer for creating lean production images. You can now use multiple FROM statements in a single Dockerfile, each starting a new build stage.

This allows you to separate your build-time dependencies from your final runtime image. You copy only the necessary artifacts from one stage to another, leaving behind all the compilers and build tools. In practice, this eliminates the need for hacks like manually cleaning up apt-get caches in the same layer, resulting in significantly smaller and more secure images.

Here's a quick example of building a Go app without the entire Go toolchain in the final image:

FROM golang:1.20 AS builder
WORKDIR /src
COPY . .
RUN go build -o /app .

FROM alpine:latest
COPY --from=builder /app /app
CMD ["/app"]

What swarm mode improvements were introduced?

Swarm mode got smarter with more granular control over service updates and node management. The docker service update command now supports --update-parallelism and --update-delay flags, giving you precise control over rolling update deployment speed.

You can also now manage node availability with docker node update --availability drain. This is crucial for planned maintenance; it gracefully stops tasks on a node and reschedules them elsewhere in the swarm without service interruption. It makes the orchestration lifecycle feel much more production-ready.

Can I assign a MAC address to a container now?

Yes, this release adds the --mac-address flag to the docker run command. This allows you to set a static MAC address for a container's network interface, which is a niche but critical requirement for certain legacy applications that use MAC-based licensing or network filtering.

Remember that the MAC address must be a valid unicast address. This isn't a feature most developers will use daily, but it's a lifesaver when you need to containerize older, less flexible software that has specific network hardware expectations.