Document in the experimental section
Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com> (cherry picked from commit a31633c2707c78c2ffd684a5a3e576f310af0fb5)
This commit is contained in:
Arnaud Porterie
David Calavera
parent
ab8a5bcf04
commit
8d0486832d
|
|
@ -0,0 +1,223 @@
|
|||
page_title: Plugin API documentation
|
||||
page_description: Documentation for writing a Docker plugin.
|
||||
page_keywords: docker, plugins, api, extensions
|
||||
|
||||
# Docker Plugin API
|
||||
|
||||
Docker plugins are out-of-process extensions which add capabilities to the
|
||||
Docker Engine.
|
||||
|
||||
This page is intended for people who want to develop their own Docker plugin.
|
||||
If you just want to learn about or use Docker plugins, look
|
||||
[here](/userguide/plugins).
|
||||
|
||||
## What plugins are
|
||||
|
||||
A plugin is a process running on the same docker host as the docker daemon,
|
||||
which registers itself by placing a file in `/usr/share/docker/plugins` (the
|
||||
"plugin directory").
|
||||
|
||||
Plugins have human-readable names, which are short, lowercase strings. For
|
||||
example, `flocker` or `weave`.
|
||||
|
||||
Plugins can run inside or outside containers. Currently running them outside
|
||||
containers is recommended.
|
||||
|
||||
## Plugin discovery
|
||||
|
||||
Docker discovers plugins by looking for them in the plugin directory whenever a
|
||||
user or container tries to use one by name.
|
||||
|
||||
There are two types of files which can be put in the plugin directory.
|
||||
|
||||
* `.sock` files are UNIX domain sockets.
|
||||
* `.spec` files are text files containing a URL, such as `unix:///other.sock`.
|
||||
|
||||
The name of the file (excluding the extension) determines the plugin name.
|
||||
|
||||
For example, the `flocker` plugin might create a UNIX socket at
|
||||
`/usr/share/docker/plugins/flocker.sock`.
|
||||
|
||||
Plugins must be run locally on the same machine as the Docker daemon. UNIX
|
||||
domain sockets are strongly encouraged for security reasons.
|
||||
|
||||
## Plugin lifecycle
|
||||
|
||||
Plugins should be started before Docker, and stopped after Docker. For
|
||||
example, when packaging a plugin for a platform which supports `systemd`, you
|
||||
might use [`systemd` dependencies](
|
||||
http://www.freedesktop.org/software/systemd/man/systemd.unit.html#Before=) to
|
||||
manage startup and shutdown order.
|
||||
|
||||
When upgrading a plugin, you should first stop the Docker daemon, upgrade the
|
||||
plugin, then start Docker again.
|
||||
|
||||
If a plugin is packaged as a container, this may cause issues. Plugins as
|
||||
containers are currently considered experimental due to these shutdown/startup
|
||||
ordering issues. These issues are mitigated by plugin retries (see below).
|
||||
|
||||
## Plugin activation
|
||||
|
||||
When a plugin is first referred to -- either by a user referring to it by name
|
||||
(e.g. `docker run --volume-driver=foo`) or a container already configured to
|
||||
use a plugin being started -- Docker looks for the named plugin in the plugin
|
||||
directory and activates it with a handshake. See Handshake API below.
|
||||
|
||||
Plugins are *not* activated automatically at Docker daemon startup. Rather,
|
||||
they are activated only lazily, or on-demand, when they are needed.
|
||||
|
||||
## API design
|
||||
|
||||
The Plugin API is RPC-style JSON over HTTP, much like webhooks.
|
||||
|
||||
Requests flow *from* the Docker daemon *to* the plugin. So the plugin needs to
|
||||
implement an HTTP server and bind this to the UNIX socket mentioned in the
|
||||
"plugin discovery" section.
|
||||
|
||||
All requests are HTTP `POST` requests.
|
||||
|
||||
The API is versioned via an Accept header, which currently is always set to
|
||||
`application/vnd.docker.plugins.v1+json`.
|
||||
|
||||
## Handshake API
|
||||
|
||||
Plugins are activated via the following "handshake" API call.
|
||||
|
||||
### /Plugin.Activate
|
||||
|
||||
**Request:** empty body
|
||||
|
||||
**Response:**
|
||||
```
|
||||
{
|
||||
"Implements": ["VolumeDriver"]
|
||||
}
|
||||
```
|
||||
|
||||
Responds with a list of Docker subsystems which this plugin implements.
|
||||
After activation, the plugin will then be sent events from this subsystem.
|
||||
|
||||
## Volume API
|
||||
|
||||
If a plugin registers itself as a `VolumeDriver` (see above) then it is
|
||||
expected to provide writeable paths on the host filesystem for the Docker
|
||||
daemon to provide to containers to consume.
|
||||
|
||||
The Docker daemon handles bind-mounting the provided paths into user
|
||||
containers.
|
||||
|
||||
### /VolumeDriver.Create
|
||||
|
||||
**Request**:
|
||||
```
|
||||
{
|
||||
"Name": "volume_name"
|
||||
}
|
||||
```
|
||||
|
||||
Instruct the plugin that the user wants to create a volume, given a user
|
||||
specified volume name. The plugin does not need to actually manifest the
|
||||
volume on the filesystem yet (until Mount is called).
|
||||
|
||||
**Response**:
|
||||
```
|
||||
{
|
||||
"Err": null
|
||||
}
|
||||
```
|
||||
|
||||
Respond with a string error if an error occurred.
|
||||
|
||||
### /VolumeDriver.Remove
|
||||
|
||||
**Request**:
|
||||
```
|
||||
{
|
||||
"Name": "volume_name"
|
||||
}
|
||||
```
|
||||
|
||||
Create a volume, given a user specified volume name.
|
||||
|
||||
**Response**:
|
||||
```
|
||||
{
|
||||
"Err": null
|
||||
}
|
||||
```
|
||||
|
||||
Respond with a string error if an error occurred.
|
||||
|
||||
### /VolumeDriver.Mount
|
||||
|
||||
**Request**:
|
||||
```
|
||||
{
|
||||
"Name": "volume_name"
|
||||
}
|
||||
```
|
||||
|
||||
Docker requires the plugin to provide a volume, given a user specified volume
|
||||
name. This is called once per container start.
|
||||
|
||||
**Response**:
|
||||
```
|
||||
{
|
||||
"Mountpoint": "/path/to/directory/on/host",
|
||||
"Err": null
|
||||
}
|
||||
```
|
||||
|
||||
Respond with the path on the host filesystem where the volume has been made
|
||||
available, and/or a string error if an error occurred.
|
||||
|
||||
### /VolumeDriver.Path
|
||||
|
||||
**Request**:
|
||||
```
|
||||
{
|
||||
"Name": "volume_name"
|
||||
}
|
||||
```
|
||||
|
||||
Docker needs reminding of the path to the volume on the host.
|
||||
|
||||
**Response**:
|
||||
```
|
||||
{
|
||||
"Mountpoint": "/path/to/directory/on/host",
|
||||
"Err": null
|
||||
}
|
||||
```
|
||||
|
||||
Respond with the path on the host filesystem where the volume has been made
|
||||
available, and/or a string error if an error occurred.
|
||||
|
||||
### /VolumeDriver.Unmount
|
||||
|
||||
**Request**:
|
||||
```
|
||||
{
|
||||
"Name": "volume_name"
|
||||
}
|
||||
```
|
||||
|
||||
Indication that Docker no longer is using the named volume. This is called once
|
||||
per container stop. Plugin may deduce that it is safe to deprovision it at
|
||||
this point.
|
||||
|
||||
**Response**:
|
||||
```
|
||||
{
|
||||
"Err": null
|
||||
}
|
||||
```
|
||||
|
||||
Respond with a string error if an error occurred.
|
||||
|
||||
## Plugin retries
|
||||
|
||||
Attempts to call a method on a plugin are retried with an exponential backoff
|
||||
for up to 30 seconds. This may help when packaging plugins as containers, since
|
||||
it gives plugin containers a chance to start up before failing any user
|
||||
containers which depend on them.
|
||||
|
|
@ -0,0 +1,46 @@
|
|||
page_title: Experimental feature - Plugins
|
||||
page_keywords: experimental, Docker, plugins
|
||||
|
||||
# Overview
|
||||
|
||||
You can extend the capabilities of the Docker Engine by loading third-party
|
||||
plugins.
|
||||
|
||||
## Types of plugins
|
||||
|
||||
Plugins extend Docker's functionality. They come in specific types. For
|
||||
example, a [volume plugin](/experimental/plugins_volume) might enable Docker
|
||||
volumes to persist across multiple Docker hosts.
|
||||
|
||||
Currently Docker supports volume plugins. In the future it will support
|
||||
additional plugin types.
|
||||
|
||||
## Installing a plugin
|
||||
|
||||
Follow the instructions in the plugin's documentation.
|
||||
|
||||
## Finding a plugin
|
||||
|
||||
The following plugins exist:
|
||||
|
||||
* The [Flocker plugin](https://clusterhq.com/docker-plugin/) is a volume plugin
|
||||
which provides multi-host portable volumes for Docker, enabling you to run
|
||||
databases and other stateful containers and move them around across a cluster
|
||||
of machines.
|
||||
|
||||
## Troubleshooting a plugin
|
||||
|
||||
If you are having problems with Docker after loading a plugin, ask the authors
|
||||
of the plugin for help. The Docker team may not be able to assist you.
|
||||
|
||||
## Writing a plugin
|
||||
|
||||
If you are interested in writing a plugin for Docker, or seeing how they work
|
||||
under the hood, see the [docker plugins reference](/experimental/plugin_api).
|
||||
|
||||
# Related GitHub PRs and issues
|
||||
|
||||
- [#13222](https://github.com/docker/docker/pull/13222) Plugins plumbing
|
||||
|
||||
Send us feedback and comments on [#13419](https://github.com/docker/docker/issues/13419),
|
||||
or on the usual Google Groups (docker-user, docker-dev) and IRC channels.
|
||||
|
|
@ -0,0 +1,43 @@
|
|||
page_title: Experimental feature - Volume plugins
|
||||
page_keywords: experimental, Docker, plugins, volume
|
||||
|
||||
# Overview
|
||||
|
||||
Docker volume plugins enable Docker deployments to be integrated with external
|
||||
storage systems, such as Amazon EBS, and enable data volumes to persist beyond
|
||||
the lifetime of a single Docker host. See the [plugin documentation](/experimental/plugins)
|
||||
for more information.
|
||||
|
||||
# Command-line changes
|
||||
|
||||
This experimental features introduces two changes to the `docker run` command:
|
||||
|
||||
- The `--volume-driver` flag is introduced.
|
||||
- The `-v` syntax is changed to accept a volume name a first component.
|
||||
|
||||
Example:
|
||||
|
||||
$ docker run -ti -v volumename:/data --volume-driver=flocker busybox sh
|
||||
|
||||
By specifying a volume name in conjunction with a volume driver, volume plugins
|
||||
such as [Flocker](https://clusterhq.com/docker-plugin/), once installed, can be
|
||||
used to manage volumes external to a single host, such as those on EBS. In this
|
||||
example, "volumename" is passed through to the volume plugin as a user-given
|
||||
name for the volume which allows the plugin to associate it with an external
|
||||
volume beyond the lifetime of a single container or container host. This can be
|
||||
used, for example, to move a stateful container from one server to another.
|
||||
|
||||
The `volumename` must not begin with a `/`.
|
||||
|
||||
# API changes
|
||||
|
||||
The container creation endpoint (`/containers/create`) accepts a `VolumeDriver`
|
||||
field of type `string` allowing to specify the name of the driver. It's default
|
||||
value of `"local"` (the default driver for local volumes).
|
||||
|
||||
# Related GitHub PRs and issues
|
||||
|
||||
- [#13161](https://github.com/docker/docker/pull/13161) Volume refactor and external volume plugins
|
||||
|
||||
Send us feedback and comments on [#13420](https://github.com/docker/docker/issues/13420),
|
||||
or on the usual Google Groups (docker-user, docker-dev) and IRC channels.
|
||||
Loading…
Reference in New Issue