cmd/dist: POC implementation of dist fetch
With this changeset we introduce several new things. The first is the
top-level dist command. This is a toolkit that implements various
distribution primitives, such as fetching, unpacking and ingesting.
The first component to this is a simple `fetch` command. It is a
low-level command that takes a "remote", identified by a `locator`, and
an object identifier. Keyed by the locator, this tool can identify a
remote implementation to fetch the content and write it back to standard
out. By allowing this to be the unit of pluggability in fetching
content, we can have quite a bit of flexibility in how we retrieve
images.
The current `fetch` implementation provides anonymous access to docker
hub images, through the namespace `docker.io`. As an example, one can
fetch the manifest for `redis` with the following command:
```
$ ./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json
```
Note that we have provided a mediatype "hint", nudging the fetch
implementation to grab the correct endpoint. We can hash the output of
that to fetch the same content by digest:
```
$ ./dist fetch docker.io/library/redis sha256:$(./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json | shasum -a256)
```
Note that the hint is now elided, since we have affixed the content to a
particular hash.
If you are not yet entertained, let's bring `jq` and `xargs` into the
mix for maximum fun. The following incantation fetches the same manifest
and downloads all layers into the convenience of `/dev/null`:
```
$ ./dist fetch docker.io/library/redis sha256:a027a470aa2b9b41cc2539847a97b8a14794ebd0a4c7c5d64e390df6bde56c73 | jq -r '.layers[] | .digest' | xargs -n1 -P10 ./dist fetch docker.io/library/redis > /dev/null
```
This is just the beginning. We should be able to centralize
configuration around fetch to implement a number of distribution
methodologies that have been challenging or impossible up to this point.
The `locator`, mentioned earlier, is a schemaless URL that provides a
host and path that can be used to resolve the remote. By dispatching on
this common identifier, we should be able to support almost any protocol
and discovery mechanism imaginable.
When this is more solidified, we can roll these up into higher-level
operations that can be orchestrated through the `dist` tool or via GRPC.
What a time to be alive!
Signed-off-by: Stephen J Day <stephen.day@docker.com>
2017-01-20 03:03:44 +00:00
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package main
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import (
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2017-02-17 08:07:02 +00:00
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contextpkg "context"
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cmd/dist: POC implementation of dist fetch
With this changeset we introduce several new things. The first is the
top-level dist command. This is a toolkit that implements various
distribution primitives, such as fetching, unpacking and ingesting.
The first component to this is a simple `fetch` command. It is a
low-level command that takes a "remote", identified by a `locator`, and
an object identifier. Keyed by the locator, this tool can identify a
remote implementation to fetch the content and write it back to standard
out. By allowing this to be the unit of pluggability in fetching
content, we can have quite a bit of flexibility in how we retrieve
images.
The current `fetch` implementation provides anonymous access to docker
hub images, through the namespace `docker.io`. As an example, one can
fetch the manifest for `redis` with the following command:
```
$ ./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json
```
Note that we have provided a mediatype "hint", nudging the fetch
implementation to grab the correct endpoint. We can hash the output of
that to fetch the same content by digest:
```
$ ./dist fetch docker.io/library/redis sha256:$(./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json | shasum -a256)
```
Note that the hint is now elided, since we have affixed the content to a
particular hash.
If you are not yet entertained, let's bring `jq` and `xargs` into the
mix for maximum fun. The following incantation fetches the same manifest
and downloads all layers into the convenience of `/dev/null`:
```
$ ./dist fetch docker.io/library/redis sha256:a027a470aa2b9b41cc2539847a97b8a14794ebd0a4c7c5d64e390df6bde56c73 | jq -r '.layers[] | .digest' | xargs -n1 -P10 ./dist fetch docker.io/library/redis > /dev/null
```
This is just the beginning. We should be able to centralize
configuration around fetch to implement a number of distribution
methodologies that have been challenging or impossible up to this point.
The `locator`, mentioned earlier, is a schemaless URL that provides a
host and path that can be used to resolve the remote. By dispatching on
this common identifier, we should be able to support almost any protocol
and discovery mechanism imaginable.
When this is more solidified, we can roll these up into higher-level
operations that can be orchestrated through the `dist` tool or via GRPC.
What a time to be alive!
Signed-off-by: Stephen J Day <stephen.day@docker.com>
2017-01-20 03:03:44 +00:00
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"fmt"
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"os"
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"github.com/Sirupsen/logrus"
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"github.com/docker/containerd"
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"github.com/urfave/cli"
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)
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2017-02-17 08:07:02 +00:00
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var (
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background = contextpkg.Background()
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)
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2017-02-25 00:09:19 +00:00
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func init() {
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2017-02-22 21:16:06 +00:00
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cli.VersionPrinter = func(c *cli.Context) {
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2017-02-25 00:09:19 +00:00
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fmt.Println(c.App.Name, containerd.Package, c.App.Version)
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2017-02-22 21:16:06 +00:00
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}
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2017-02-25 00:09:19 +00:00
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}
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func main() {
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cmd/dist: POC implementation of dist fetch
With this changeset we introduce several new things. The first is the
top-level dist command. This is a toolkit that implements various
distribution primitives, such as fetching, unpacking and ingesting.
The first component to this is a simple `fetch` command. It is a
low-level command that takes a "remote", identified by a `locator`, and
an object identifier. Keyed by the locator, this tool can identify a
remote implementation to fetch the content and write it back to standard
out. By allowing this to be the unit of pluggability in fetching
content, we can have quite a bit of flexibility in how we retrieve
images.
The current `fetch` implementation provides anonymous access to docker
hub images, through the namespace `docker.io`. As an example, one can
fetch the manifest for `redis` with the following command:
```
$ ./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json
```
Note that we have provided a mediatype "hint", nudging the fetch
implementation to grab the correct endpoint. We can hash the output of
that to fetch the same content by digest:
```
$ ./dist fetch docker.io/library/redis sha256:$(./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json | shasum -a256)
```
Note that the hint is now elided, since we have affixed the content to a
particular hash.
If you are not yet entertained, let's bring `jq` and `xargs` into the
mix for maximum fun. The following incantation fetches the same manifest
and downloads all layers into the convenience of `/dev/null`:
```
$ ./dist fetch docker.io/library/redis sha256:a027a470aa2b9b41cc2539847a97b8a14794ebd0a4c7c5d64e390df6bde56c73 | jq -r '.layers[] | .digest' | xargs -n1 -P10 ./dist fetch docker.io/library/redis > /dev/null
```
This is just the beginning. We should be able to centralize
configuration around fetch to implement a number of distribution
methodologies that have been challenging or impossible up to this point.
The `locator`, mentioned earlier, is a schemaless URL that provides a
host and path that can be used to resolve the remote. By dispatching on
this common identifier, we should be able to support almost any protocol
and discovery mechanism imaginable.
When this is more solidified, we can roll these up into higher-level
operations that can be orchestrated through the `dist` tool or via GRPC.
What a time to be alive!
Signed-off-by: Stephen J Day <stephen.day@docker.com>
2017-01-20 03:03:44 +00:00
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app := cli.NewApp()
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app.Name = "dist"
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app.Version = containerd.Version
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app.Usage = `
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___ __
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____/ (_)____/ /_
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/ __ / / ___/ __/
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/ /_/ / (__ ) /_
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\__,_/_/____/\__/
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distribution tool
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`
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app.Flags = []cli.Flag{
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cli.BoolFlag{
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Name: "debug",
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Usage: "enable debug output in logs",
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},
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2017-02-17 08:07:02 +00:00
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cli.DurationFlag{
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2017-03-01 00:43:08 +00:00
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Name: "timeout",
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Usage: "total timeout for dist commands",
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},
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cli.DurationFlag{
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Name: "connect-timeout",
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Usage: "timeout for connecting to containerd",
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2017-02-17 08:07:02 +00:00
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},
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cli.StringFlag{
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2017-02-22 07:41:11 +00:00
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// TODO(stevvooe): for now, we allow circumventing the GRPC. Once
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// we have clear separation, this will likely go away.
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2017-02-17 08:07:02 +00:00
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Name: "root",
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Usage: "path to content store root",
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2017-02-22 07:41:11 +00:00
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Value: "/var/lib/containerd",
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2017-02-17 08:07:02 +00:00
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},
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2017-02-18 00:49:59 +00:00
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cli.StringFlag{
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Name: "socket, s",
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Usage: "socket path for containerd's GRPC server",
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Value: "/run/containerd/containerd.sock",
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},
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cmd/dist: POC implementation of dist fetch
With this changeset we introduce several new things. The first is the
top-level dist command. This is a toolkit that implements various
distribution primitives, such as fetching, unpacking and ingesting.
The first component to this is a simple `fetch` command. It is a
low-level command that takes a "remote", identified by a `locator`, and
an object identifier. Keyed by the locator, this tool can identify a
remote implementation to fetch the content and write it back to standard
out. By allowing this to be the unit of pluggability in fetching
content, we can have quite a bit of flexibility in how we retrieve
images.
The current `fetch` implementation provides anonymous access to docker
hub images, through the namespace `docker.io`. As an example, one can
fetch the manifest for `redis` with the following command:
```
$ ./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json
```
Note that we have provided a mediatype "hint", nudging the fetch
implementation to grab the correct endpoint. We can hash the output of
that to fetch the same content by digest:
```
$ ./dist fetch docker.io/library/redis sha256:$(./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json | shasum -a256)
```
Note that the hint is now elided, since we have affixed the content to a
particular hash.
If you are not yet entertained, let's bring `jq` and `xargs` into the
mix for maximum fun. The following incantation fetches the same manifest
and downloads all layers into the convenience of `/dev/null`:
```
$ ./dist fetch docker.io/library/redis sha256:a027a470aa2b9b41cc2539847a97b8a14794ebd0a4c7c5d64e390df6bde56c73 | jq -r '.layers[] | .digest' | xargs -n1 -P10 ./dist fetch docker.io/library/redis > /dev/null
```
This is just the beginning. We should be able to centralize
configuration around fetch to implement a number of distribution
methodologies that have been challenging or impossible up to this point.
The `locator`, mentioned earlier, is a schemaless URL that provides a
host and path that can be used to resolve the remote. By dispatching on
this common identifier, we should be able to support almost any protocol
and discovery mechanism imaginable.
When this is more solidified, we can roll these up into higher-level
operations that can be orchestrated through the `dist` tool or via GRPC.
What a time to be alive!
Signed-off-by: Stephen J Day <stephen.day@docker.com>
2017-01-20 03:03:44 +00:00
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}
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app.Commands = []cli.Command{
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cmd/dist, cmd/ctr: end to end image pull
With this changeset, we now have a proof of concept of end to end pull.
Up to this point, the relationship between subsystems has been somewhat
theoretical. We now leverage fetching, the snapshot drivers, the rootfs
service, image metadata and the execution service, validating the proposed
model for containerd. There are a few caveats, including the need to move some
of the access into GRPC services, but the basic components are there.
The first command we will cover here is `dist pull`. This is the analog
of `docker pull` and `git pull`. It performs a full resource fetch for
an image and unpacks the root filesystem into the snapshot drivers. An
example follows:
``` console
$ sudo ./bin/dist pull docker.io/library/redis:latest
docker.io/library/redis:latest: resolved |++++++++++++++++++++++++++++++++++++++|
manifest-sha256:4c8fb09e8d634ab823b1c125e64f0e1ceaf216025aa38283ea1b42997f1e8059: done |++++++++++++++++++++++++++++++++++++++|
layer-sha256:3b281f2bcae3b25c701d53a219924fffe79bdb74385340b73a539ed4020999c4: done |++++++++++++++++++++++++++++++++++++++|
config-sha256:e4a35914679d05d25e2fccfd310fde1aa59ffbbf1b0b9d36f7b03db5ca0311b0: done |++++++++++++++++++++++++++++++++++++++|
layer-sha256:4b7726832aec75f0a742266c7190c4d2217492722dfd603406208eaa902648d8: done |++++++++++++++++++++++++++++++++++++++|
layer-sha256:338a7133395941c85087522582af182d2f6477dbf54ba769cb24ec4fd91d728f: done |++++++++++++++++++++++++++++++++++++++|
layer-sha256:83f12ff60ff1132d1e59845e26c41968406b4176c1a85a50506c954696b21570: done |++++++++++++++++++++++++++++++++++++++|
layer-sha256:693502eb7dfbc6b94964ae66ebc72d3e32facd981c72995b09794f1e87bac184: done |++++++++++++++++++++++++++++++++++++++|
layer-sha256:622732cddc347afc9360b4b04b46c6f758191a1dc73d007f95548658847ee67e: done |++++++++++++++++++++++++++++++++++++++|
layer-sha256:19a7e34366a6f558336c364693df538c38307484b729a36fede76432789f084f: done |++++++++++++++++++++++++++++++++++++++|
elapsed: 1.6 s total: 0.0 B (0.0 B/s)
INFO[0001] unpacking rootfs
```
Note that we haven't integrated rootfs unpacking into the status output, but we
pretty much have what is in docker today (:P). We can see the result of our pull
with the following:
```console
$ sudo ./bin/dist images
REF TYPE DIGEST SIZE
docker.io/library/redis:latest application/vnd.docker.distribution.manifest.v2+json sha256:4c8fb09e8d634ab823b1c125e64f0e1ceaf216025aa38283ea1b42997f1e8059 1.8 kB
```
The above shows that we have an image called "docker.io/library/redis:latest"
mapped to the given digest marked with a specific format. We get the size of
the manifest right now, not the full image, but we can add more as we need it.
For the most part, this is all that is needed, but a few tweaks to the model
for naming may need to be added. Specifically, we may want to index under a few
different names, including those qualified by hash or matched by tag versions.
We can do more work in this area as we develop the metadata store.
The name shown above can then be used to run the actual container image. We can
do this with the following command:
```console
$ sudo ./bin/ctr run --id foo docker.io/library/redis:latest /usr/local/bin/redis-server
1:C 17 Mar 17:20:25.316 # Warning: no config file specified, using the default config. In order to specify a config file use /usr/local/bin/redis-server /path/to/redis.conf
1:M 17 Mar 17:20:25.317 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 3.2.8 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in standalone mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 6379
| `-._ `._ / _.-' | PID: 1
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
1:M 17 Mar 17:20:25.326 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
1:M 17 Mar 17:20:25.326 # Server started, Redis version 3.2.8
1:M 17 Mar 17:20:25.326 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
1:M 17 Mar 17:20:25.326 # WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled.
1:M 17 Mar 17:20:25.326 * The server is now ready to accept connections on port 6379
```
Wow! So, now we are running `redis`!
There are still a few things to work out. Notice that we have to specify the
command as part of the arguments to `ctr run`. This is because are not yet
reading the image config and converting it to an OCI runtime config. With the
base laid in this PR, adding such functionality should be straightforward.
While this is a _little_ messy, this is great progress. It should be easy
sailing from here.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
2017-03-18 00:00:52 +00:00
|
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imagesCommand,
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|
|
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|
pullCommand,
|
2017-03-02 22:41:51 +00:00
|
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|
fetchCommand,
|
2017-03-02 21:50:09 +00:00
|
|
|
fetchObjectCommand,
|
dist: expand functionality of the dist tool
With this change, we add the following commands to the dist tool:
- `ingest`: verify and accept content into storage
- `active`: display active ingest processes
- `list`: list content in storage
- `path`: provide a path to a blob by digest
- `delete`: remove a piece of content from storage
We demonstrate the utility with the following shell pipeline:
```
$ ./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json | \
jq -r '.layers[] | "./dist fetch docker.io/library/redis "+.digest + "| ./dist ingest --expected-digest "+.digest+" --expected-size "+(.size | tostring) +" docker.io/library/redis@"+.digest' | xargs -I{} -P10 -n1 sh -c "{}"
```
The above fetches a manifest, pipes it to jq, which assembles a shell
pipeline to ingest each layer into the content store. Because the
transactions are keyed by their digest, concurrent downloads and
downloads of repeated content are ignored. Each process is then executed
parallel using xargs.
Put shortly, this is a parallel layer download.
In a separate shell session, could monitor the active downloads with the
following:
```
$ watch -n0.2 ./dist active
```
For now, the content is downloaded into `.content` in the current
working directory. To watch the contents of this directory, you can use
the following:
```
$ watch -n0.2 tree .content
```
This will help to understand what is going on internally.
To get access to the layers, you can use the path command:
```
$./dist path sha256:010c454d55e53059beaba4044116ea4636f8dd8181e975d893931c7e7204fffa
sha256:010c454d55e53059beaba4044116ea4636f8dd8181e975d893931c7e7204fffa /home/sjd/go/src/github.com/docker/containerd/.content/blobs/sha256/010c454d55e53059beaba4044116ea4636f8dd8181e975d893931c7e7204fffa
```
When you are done, you can clear out the content with the classic xargs
pipeline:
```
$ ./dist list -q | xargs ./dist delete
```
Note that this is mostly a POC. Things like failed downloads and
abandoned download cleanup aren't quite handled. We'll probably make
adjustments around how content store transactions are handled to address
this.
From here, we'll build out full image pull and create tooling to get
runtime bundles from the fetched content.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
2017-01-26 22:08:56 +00:00
|
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ingestCommand,
|
|
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|
|
activeCommand,
|
2017-02-17 08:07:02 +00:00
|
|
|
getCommand,
|
dist: expand functionality of the dist tool
With this change, we add the following commands to the dist tool:
- `ingest`: verify and accept content into storage
- `active`: display active ingest processes
- `list`: list content in storage
- `path`: provide a path to a blob by digest
- `delete`: remove a piece of content from storage
We demonstrate the utility with the following shell pipeline:
```
$ ./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json | \
jq -r '.layers[] | "./dist fetch docker.io/library/redis "+.digest + "| ./dist ingest --expected-digest "+.digest+" --expected-size "+(.size | tostring) +" docker.io/library/redis@"+.digest' | xargs -I{} -P10 -n1 sh -c "{}"
```
The above fetches a manifest, pipes it to jq, which assembles a shell
pipeline to ingest each layer into the content store. Because the
transactions are keyed by their digest, concurrent downloads and
downloads of repeated content are ignored. Each process is then executed
parallel using xargs.
Put shortly, this is a parallel layer download.
In a separate shell session, could monitor the active downloads with the
following:
```
$ watch -n0.2 ./dist active
```
For now, the content is downloaded into `.content` in the current
working directory. To watch the contents of this directory, you can use
the following:
```
$ watch -n0.2 tree .content
```
This will help to understand what is going on internally.
To get access to the layers, you can use the path command:
```
$./dist path sha256:010c454d55e53059beaba4044116ea4636f8dd8181e975d893931c7e7204fffa
sha256:010c454d55e53059beaba4044116ea4636f8dd8181e975d893931c7e7204fffa /home/sjd/go/src/github.com/docker/containerd/.content/blobs/sha256/010c454d55e53059beaba4044116ea4636f8dd8181e975d893931c7e7204fffa
```
When you are done, you can clear out the content with the classic xargs
pipeline:
```
$ ./dist list -q | xargs ./dist delete
```
Note that this is mostly a POC. Things like failed downloads and
abandoned download cleanup aren't quite handled. We'll probably make
adjustments around how content store transactions are handled to address
this.
From here, we'll build out full image pull and create tooling to get
runtime bundles from the fetched content.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
2017-01-26 22:08:56 +00:00
|
|
|
deleteCommand,
|
|
|
|
|
listCommand,
|
2017-01-27 19:00:29 +00:00
|
|
|
applyCommand,
|
2017-03-09 06:04:44 +00:00
|
|
|
rootfsCommand,
|
cmd/dist: POC implementation of dist fetch
With this changeset we introduce several new things. The first is the
top-level dist command. This is a toolkit that implements various
distribution primitives, such as fetching, unpacking and ingesting.
The first component to this is a simple `fetch` command. It is a
low-level command that takes a "remote", identified by a `locator`, and
an object identifier. Keyed by the locator, this tool can identify a
remote implementation to fetch the content and write it back to standard
out. By allowing this to be the unit of pluggability in fetching
content, we can have quite a bit of flexibility in how we retrieve
images.
The current `fetch` implementation provides anonymous access to docker
hub images, through the namespace `docker.io`. As an example, one can
fetch the manifest for `redis` with the following command:
```
$ ./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json
```
Note that we have provided a mediatype "hint", nudging the fetch
implementation to grab the correct endpoint. We can hash the output of
that to fetch the same content by digest:
```
$ ./dist fetch docker.io/library/redis sha256:$(./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json | shasum -a256)
```
Note that the hint is now elided, since we have affixed the content to a
particular hash.
If you are not yet entertained, let's bring `jq` and `xargs` into the
mix for maximum fun. The following incantation fetches the same manifest
and downloads all layers into the convenience of `/dev/null`:
```
$ ./dist fetch docker.io/library/redis sha256:a027a470aa2b9b41cc2539847a97b8a14794ebd0a4c7c5d64e390df6bde56c73 | jq -r '.layers[] | .digest' | xargs -n1 -P10 ./dist fetch docker.io/library/redis > /dev/null
```
This is just the beginning. We should be able to centralize
configuration around fetch to implement a number of distribution
methodologies that have been challenging or impossible up to this point.
The `locator`, mentioned earlier, is a schemaless URL that provides a
host and path that can be used to resolve the remote. By dispatching on
this common identifier, we should be able to support almost any protocol
and discovery mechanism imaginable.
When this is more solidified, we can roll these up into higher-level
operations that can be orchestrated through the `dist` tool or via GRPC.
What a time to be alive!
Signed-off-by: Stephen J Day <stephen.day@docker.com>
2017-01-20 03:03:44 +00:00
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}
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app.Before = func(context *cli.Context) error {
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2017-02-17 08:07:02 +00:00
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var (
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debug = context.GlobalBool("debug")
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timeout = context.GlobalDuration("timeout")
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)
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if debug {
|
cmd/dist: POC implementation of dist fetch
With this changeset we introduce several new things. The first is the
top-level dist command. This is a toolkit that implements various
distribution primitives, such as fetching, unpacking and ingesting.
The first component to this is a simple `fetch` command. It is a
low-level command that takes a "remote", identified by a `locator`, and
an object identifier. Keyed by the locator, this tool can identify a
remote implementation to fetch the content and write it back to standard
out. By allowing this to be the unit of pluggability in fetching
content, we can have quite a bit of flexibility in how we retrieve
images.
The current `fetch` implementation provides anonymous access to docker
hub images, through the namespace `docker.io`. As an example, one can
fetch the manifest for `redis` with the following command:
```
$ ./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json
```
Note that we have provided a mediatype "hint", nudging the fetch
implementation to grab the correct endpoint. We can hash the output of
that to fetch the same content by digest:
```
$ ./dist fetch docker.io/library/redis sha256:$(./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json | shasum -a256)
```
Note that the hint is now elided, since we have affixed the content to a
particular hash.
If you are not yet entertained, let's bring `jq` and `xargs` into the
mix for maximum fun. The following incantation fetches the same manifest
and downloads all layers into the convenience of `/dev/null`:
```
$ ./dist fetch docker.io/library/redis sha256:a027a470aa2b9b41cc2539847a97b8a14794ebd0a4c7c5d64e390df6bde56c73 | jq -r '.layers[] | .digest' | xargs -n1 -P10 ./dist fetch docker.io/library/redis > /dev/null
```
This is just the beginning. We should be able to centralize
configuration around fetch to implement a number of distribution
methodologies that have been challenging or impossible up to this point.
The `locator`, mentioned earlier, is a schemaless URL that provides a
host and path that can be used to resolve the remote. By dispatching on
this common identifier, we should be able to support almost any protocol
and discovery mechanism imaginable.
When this is more solidified, we can roll these up into higher-level
operations that can be orchestrated through the `dist` tool or via GRPC.
What a time to be alive!
Signed-off-by: Stephen J Day <stephen.day@docker.com>
2017-01-20 03:03:44 +00:00
|
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|
logrus.SetLevel(logrus.DebugLevel)
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|
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|
}
|
2017-02-17 08:07:02 +00:00
|
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|
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|
|
|
|
if timeout > 0 {
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|
background, _ = contextpkg.WithTimeout(background, timeout)
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}
|
cmd/dist: POC implementation of dist fetch
With this changeset we introduce several new things. The first is the
top-level dist command. This is a toolkit that implements various
distribution primitives, such as fetching, unpacking and ingesting.
The first component to this is a simple `fetch` command. It is a
low-level command that takes a "remote", identified by a `locator`, and
an object identifier. Keyed by the locator, this tool can identify a
remote implementation to fetch the content and write it back to standard
out. By allowing this to be the unit of pluggability in fetching
content, we can have quite a bit of flexibility in how we retrieve
images.
The current `fetch` implementation provides anonymous access to docker
hub images, through the namespace `docker.io`. As an example, one can
fetch the manifest for `redis` with the following command:
```
$ ./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json
```
Note that we have provided a mediatype "hint", nudging the fetch
implementation to grab the correct endpoint. We can hash the output of
that to fetch the same content by digest:
```
$ ./dist fetch docker.io/library/redis sha256:$(./dist fetch docker.io/library/redis latest mediatype:application/vnd.docker.distribution.manifest.v2+json | shasum -a256)
```
Note that the hint is now elided, since we have affixed the content to a
particular hash.
If you are not yet entertained, let's bring `jq` and `xargs` into the
mix for maximum fun. The following incantation fetches the same manifest
and downloads all layers into the convenience of `/dev/null`:
```
$ ./dist fetch docker.io/library/redis sha256:a027a470aa2b9b41cc2539847a97b8a14794ebd0a4c7c5d64e390df6bde56c73 | jq -r '.layers[] | .digest' | xargs -n1 -P10 ./dist fetch docker.io/library/redis > /dev/null
```
This is just the beginning. We should be able to centralize
configuration around fetch to implement a number of distribution
methodologies that have been challenging or impossible up to this point.
The `locator`, mentioned earlier, is a schemaless URL that provides a
host and path that can be used to resolve the remote. By dispatching on
this common identifier, we should be able to support almost any protocol
and discovery mechanism imaginable.
When this is more solidified, we can roll these up into higher-level
operations that can be orchestrated through the `dist` tool or via GRPC.
What a time to be alive!
Signed-off-by: Stephen J Day <stephen.day@docker.com>
2017-01-20 03:03:44 +00:00
|
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|
return nil
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|
}
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if err := app.Run(os.Args); err != nil {
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fmt.Fprintf(os.Stderr, "dist: %s\n", err)
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os.Exit(1)
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}
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}
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