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Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com>
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Arnaud Porterie 2016-02-17 12:55:20 -08:00
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ROADMAP.md
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@ -33,97 +33,58 @@ won't be accepting pull requests adding or removing items from this file.
# 1. Features and refactoring
## 1.1 Security
## 1.1 Runtime improvements
Security is a top objective for the Docker Engine. The most notable items we intend to provide in
the near future are:
We recently introduced [`runC`](https://runc.io) as a standalone low-level tool for container
execution. The initial goal was to integrate runC as a replacement in the Engine for the traditional
default libcontainer `execdriver`, but the Engine internals were not ready for this.
- Trusted distribution of images: the effort is driven by the [distribution](https://github.com/docker/distribution)
group but will have significant impact on the Engine
- [User namespaces](https://github.com/docker/docker/pull/12648)
- [Seccomp support](https://github.com/docker/libcontainer/pull/613)
As runC continued evolving, and the OCI specification along with it, we created
[`containerd`](https://containerd.tools/), a daemon to control and monitor multiple `runC`. This is
the new target for Engine integration, as it can entirely replace the whole `execdriver`
architecture, and container monitoring along with it.
## 1.2 Plumbing project
Docker Engine will rely on a long-running `containerd` companion daemon for all container execution
related operations. This could open the door in the future for Engine restarts without interrupting
running containers.
We define a plumbing tool as a standalone piece of software usable and meaningful on its own. In
the current state of the Docker Engine, most subsystems provide independent functionalities (such
the builder, pushing and pulling images, running applications in a containerized environment, etc)
but all are coupled in a single binary. We want to offer the users to flexibility to use only the
pieces they need, and we will also gain in maintainability by splitting the project among multiple
repositories.
## 1.2 Plugins improvements
As it currently stands, the rough design outlines is to have:
- Low level plumbing tools, each dealing with one responsibility (e.g., [runC](https://runc.io))
- Docker subsystems services, each exposing an elementary concept over an API, and relying on one or
multiple lower level plumbing tools for their implementation (e.g., network management)
- Docker Engine to expose higher level actions (e.g., create a container with volume `V` and network
`N`), while still providing pass-through access to the individual subsystems.
Docker Engine 1.7.0 introduced plugin support, initially for the use cases of volumes and networks
extensions. The plugin infrastructure was kept minimal as we were collecting use cases and real
world feedback before optimizing for any particular workflow.
The architectural details are still being worked on, but one thing we know for sure is that we need
to technically decouple the pieces.
In the future, we'd like plugins to become first class citizens, and encourage an ecosystem of
plugins. This implies in particular making it trivially easy to distribute plugins as containers
through any Registry instance, as well as solving the commonly heard pain points of plugins needing
to be treated as somewhat special (being active at all time, started before any other user
containers, and not as easily dismissed).
### 1.2.1 Runtime
## 1.3 Internal decoupling
A Runtime tool already exists today in the form of [runC](https://github.com/opencontainers/runc).
We intend to modify the Engine to directly call out to a binary implementing the Open Containers
Specification such as runC rather than relying on libcontainer to set the container runtime up.
A lot of work has been done in trying to decouple the Docker Engine's internals. In particular, the
API implementation has been refactored and ongoing work is happening to move the code to a separate
repository ([`docker/engine-api`](https://github.com/docker/engine-api)), and the Builder side of
the daemon is now [fully independent](https://github.com/docker/docker/tree/master/builder) while
still residing in the same repository.
This plan will deprecate the existing [`execdriver`](https://github.com/docker/docker/tree/master/daemon/execdriver)
as different runtime backends will be implemented as separated binaries instead of being compiled
into the Engine.
We are exploring ways to go further with that decoupling, capitalizing on the work introduced by the
runtime renovation and plugins improvement efforts. Indeed, the combination of `containerd` support
with the concept of "special" containers opens the door for bootstrapping more Engine internals
using the same facilities.
### 1.2.2 Builder
## 1.4 Cluster capable Engine
The Builder (i.e., the ability to build an image from a Dockerfile) is already nicely decoupled,
but would benefit from being entirely separated from the Engine, and rely on the standard Engine
API for its operations.
The community has been pushing for a more cluster capable Docker Engine, and a huge effort was spent
adding features such as multihost networking, and node discovery down at the Engine level. Yet, the
Engine is currently incapable of taking scheduling decisions alone, and continues relying on Swarm
for that.
### 1.2.3 Distribution
Distribution already has a [dedicated repository](https://github.com/docker/distribution) which
holds the implementation for Registry v2 and client libraries. We could imagine going further by
having the Engine call out to a binary providing image distribution related functionalities.
There are two short term goals related to image distribution. The first is stabilize and simplify
the push/pull code. Following that is the conversion to the more secure Registry V2 protocol.
### 1.2.4 Networking
Most of networking related code was already decoupled today in [libnetwork](https://github.com/docker/libnetwork).
As with other ingredients, we might want to take it a step further and make it a meaningful utility
that the Engine would call out to instead of a library.
## 1.3 Plugins
An initiative around plugins started with Docker 1.7.0, with the goal of allowing for out of
process extensibility of some Docker functionalities, starting with volumes and networking. The
approach is to provide specific extension points rather than generic hooking facilities. We also
deliberately keep the extensions API the simplest possible, expanding as we discover valid use
cases that cannot be implemented.
At the time of writing:
- Plugin support is merged as an experimental feature: real world use cases and user feedback will
help us refine the UX to make the feature more user friendly.
- There are no immediate plans to expand on the number of pluggable subsystems.
- Golang 1.5 might add language support for [plugins](https://docs.google.com/document/d/1nr-TQHw_er6GOQRsF6T43GGhFDelrAP0NqSS_00RgZQ)
which we consider supporting as an alternative to JSON/HTTP.
## 1.4 Volume management
Volumes are not a first class citizen in the Engine today: we would like better volume management,
similar to the way network are managed in the new [CNM](https://github.com/docker/docker/issues/9983).
## 1.5 Better API implementation
The current Engine API is insufficiently typed, versioned, and ultimately hard to maintain. We
also suffer from the lack of a common implementation with [Swarm](https://github.com/docker/swarm).
## 1.6 Checkpoint/restore
Support for checkpoint/restore was [merged](https://github.com/docker/libcontainer/pull/479) in
[libcontainer](https://github.com/docker/libcontainer) and made available through [runC](https://runc.io):
we intend to take advantage of it in the Engine.
We plan to complete this effort and make Engine fully cluster capable. Multiple instances of the
Docker Engine being already capable of discovering each other and establish overlay networking for
their container to communicate, the next step is for a given Engine to gain ability to dispatch work
to another node in the cluster. This will be introduced in a backward compatible way, such that a
`docker run` invocation on a particular node remains fully deterministic.
# 2 Frozen features
@ -139,45 +100,41 @@ The Dockerfile syntax as we know it is simple, and has proven successful in supp
definitive move, we temporarily won't accept more patches to the Dockerfile syntax for several
reasons:
- Long term impact of syntax changes is a sensitive matter that require an amount of attention
the volume of Engine codebase and activity today doesn't allow us to provide.
- Allowing the Builder to be implemented as a separate utility consuming the Engine's API will
open the door for many possibilities, such as offering alternate syntaxes or DSL for existing
languages without cluttering the Engine's codebase.
- A standalone Builder will also offer the opportunity for a better dedicated group of maintainers
to own the Dockerfile syntax and decide collectively on the direction to give it.
- Our experience with official images tend to show that no new instruction or syntax expansion is
*strictly* necessary for the majority of use cases, and although we are aware many things are still
lacking for many, we cannot make it a priority yet for the above reasons.
- Long term impact of syntax changes is a sensitive matter that require an amount of attention the
volume of Engine codebase and activity today doesn't allow us to provide.
- Allowing the Builder to be implemented as a separate utility consuming the Engine's API will
open the door for many possibilities, such as offering alternate syntaxes or DSL for existing
languages without cluttering the Engine's codebase.
- A standalone Builder will also offer the opportunity for a better dedicated group of maintainers
to own the Dockerfile syntax and decide collectively on the direction to give it.
- Our experience with official images tend to show that no new instruction or syntax expansion is
*strictly* necessary for the majority of use cases, and although we are aware many things are
still lacking for many, we cannot make it a priority yet for the above reasons.
Again, this is not about saying that the Dockerfile syntax is done, it's about making choices about
what we want to do first!
## 2.3 Remote Registry Operations
A large amount of work is ongoing in the area of image distribution and
provenance. This includes moving to the V2 Registry API and heavily
refactoring the code that powers these features. The desired result is more
secure, reliable and easier to use image distribution.
A large amount of work is ongoing in the area of image distribution and provenance. This includes
moving to the V2 Registry API and heavily refactoring the code that powers these features. The
desired result is more secure, reliable and easier to use image distribution.
Part of the problem with this part of the code base is the lack of a stable
and flexible interface. If new features are added that access the registry
without solidifying these interfaces, achieving feature parity will continue
to be elusive. While we get a handle on this situation, we are imposing a
moratorium on new code that accesses the Registry API in commands that don't
already make remote calls.
Part of the problem with this part of the code base is the lack of a stable and flexible interface.
If new features are added that access the registry without solidifying these interfaces, achieving
feature parity will continue to be elusive. While we get a handle on this situation, we are imposing
a moratorium on new code that accesses the Registry API in commands that don't already make remote
calls.
Currently, only the following commands cause interaction with a remote
registry:
Currently, only the following commands cause interaction with a remote registry:
- push
- pull
- run
- build
- search
- login
- push
- pull
- run
- build
- search
- login
In the interest of stabilizing the registry access model during this ongoing
work, we are not accepting additions to other commands that will cause remote
interaction with the Registry API. This moratorium will lift when the goals of
the distribution project have been met.
In the interest of stabilizing the registry access model during this ongoing work, we are not
accepting additions to other commands that will cause remote interaction with the Registry API. This
moratorium will lift when the goals of the distribution project have been met.