119 lines
6.1 KiB
Markdown
119 lines
6.1 KiB
Markdown
Docker Engine Roadmap
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=====================
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### How should I use this document?
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This document provides description of items that the project decided to prioritize. This should
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serve as a reference point for Docker contributors to understand where the project is going, and
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help determine if a contribution could be conflicting with some longer terms plans.
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The fact that a feature isn't listed here doesn't mean that a patch for it will automatically be
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refused (except for those mentioned as "frozen features" below)! We are always happy to receive
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patches for new cool features we haven't thought about, or didn't judge priority. Please however
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understand that such patches might take longer for us to review.
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### How can I help?
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Short term objectives are listed in the [wiki](https://github.com/docker/docker/wiki) and described
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in [Issues](https://github.com/docker/docker/issues?q=is%3Aopen+is%3Aissue+label%3Aroadmap). Our
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goal is to split down the workload in such way that anybody can jump in and help. Please comment on
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issues if you want to take it to avoid duplicating effort! Similarly, if a maintainer is already
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assigned on an issue you'd like to participate in, pinging him on IRC or GitHub to offer your help is
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the best way to go.
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### How can I add something to the roadmap?
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The roadmap process is new to the Docker Engine: we are only beginning to structure and document the
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project objectives. Our immediate goal is to be more transparent, and work with our community to
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focus our efforts on fewer prioritized topics.
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We hope to offer in the near future a process allowing anyone to propose a topic to the roadmap, but
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we are not quite there yet. For the time being, the BDFL remains the keeper of the roadmap, and we
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won't be accepting pull requests adding or removing items from this file.
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# 1. Features and refactoring
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## 1.1 Runtime improvements
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We recently introduced [`runC`](https://runc.io) as a standalone low-level tool for container
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execution. The initial goal was to integrate runC as a replacement in the Engine for the traditional
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default libcontainer `execdriver`, but the Engine internals were not ready for this.
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As runC continued evolving, and the OCI specification along with it, we created
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[`containerd`](https://containerd.tools/), a daemon to control and monitor multiple `runC`. This is
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the new target for Engine integration, as it can entirely replace the whole `execdriver`
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architecture, and container monitoring along with it.
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Docker Engine will rely on a long-running `containerd` companion daemon for all container execution
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related operations. This could open the door in the future for Engine restarts without interrupting
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running containers.
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## 1.2 Plugins improvements
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Docker Engine 1.7.0 introduced plugin support, initially for the use cases of volumes and networks
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extensions. The plugin infrastructure was kept minimal as we were collecting use cases and real
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world feedback before optimizing for any particular workflow.
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In the future, we'd like plugins to become first class citizens, and encourage an ecosystem of
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plugins. This implies in particular making it trivially easy to distribute plugins as containers
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through any Registry instance, as well as solving the commonly heard pain points of plugins needing
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to be treated as somewhat special (being active at all time, started before any other user
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containers, and not as easily dismissed).
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## 1.3 Internal decoupling
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A lot of work has been done in trying to decouple the Docker Engine's internals. In particular, the
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API implementation has been refactored, and the Builder side of the daemon is now
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[fully independent](https://github.com/docker/docker/tree/master/builder) while still residing in
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the same repository.
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We are exploring ways to go further with that decoupling, capitalizing on the work introduced by the
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runtime renovation and plugins improvement efforts. Indeed, the combination of `containerd` support
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with the concept of "special" containers opens the door for bootstrapping more Engine internals
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using the same facilities.
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## 1.4 Cluster capable Engine
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The community has been pushing for a more cluster capable Docker Engine, and a huge effort was spent
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adding features such as multihost networking, and node discovery down at the Engine level. Yet, the
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Engine is currently incapable of taking scheduling decisions alone, and continues relying on Swarm
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for that.
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We plan to complete this effort and make Engine fully cluster capable. Multiple instances of the
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Docker Engine being already capable of discovering each other and establish overlay networking for
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their container to communicate, the next step is for a given Engine to gain ability to dispatch work
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to another node in the cluster. This will be introduced in a backward compatible way, such that a
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`docker run` invocation on a particular node remains fully deterministic.
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# 2. Frozen features
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## 2.1 Docker exec
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We won't accept patches expanding the surface of `docker exec`, which we intend to keep as a
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*debugging* feature, as well as being strongly dependent on the Runtime ingredient effort.
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## 2.2 Remote Registry Operations
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A large amount of work is ongoing in the area of image distribution and provenance. This includes
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moving to the V2 Registry API and heavily refactoring the code that powers these features. The
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desired result is more secure, reliable and easier to use image distribution.
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Part of the problem with this part of the code base is the lack of a stable and flexible interface.
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If new features are added that access the registry without solidifying these interfaces, achieving
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feature parity will continue to be elusive. While we get a handle on this situation, we are imposing
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a moratorium on new code that accesses the Registry API in commands that don't already make remote
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calls.
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Currently, only the following commands cause interaction with a remote registry:
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- push
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- pull
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- run
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- build
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- search
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- login
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In the interest of stabilizing the registry access model during this ongoing work, we are not
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accepting additions to other commands that will cause remote interaction with the Registry API. This
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moratorium will lift when the goals of the distribution project have been met.
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