Implementação de comandos docker pull e docker push sem cliente docker via solicitações HTTP

Nós tínhamos 2 sacos de grama, 75 comprimidos de mescalina ambiente unix, repositório do docker e tarefa para implementar comandos pull e pull do docker sem o cliente do docker.

UPD:
Pergunta: Para que serve tudo isso?
Resposta: Teste de carga do produto (NÃO por meio do bash, os scripts são fornecidos para fins educacionais). Foi decidido não usar o cliente do docker para reduzir camadas adicionais (dentro de limites razoáveis) e, consequentemente, emular uma carga mais alta. Como resultado, todos os atrasos do sistema do cliente docker foram removidos. Recebeu uma carga relativamente limpa diretamente no produto

Primeiro, vamos ver o que essas equipes fazem.

Então, para que é utilizado o docker pull? De acordo com a documentação :

"Puxe uma imagem ou um repositório de um registro".

Lá, encontramos um link para entender imagens, contêineres e drivers de armazenamento .

docker image layers, , . registry API.

:

"An “image” is a combination of a JSON manifest and individual layer files. The process of pulling an > image centers around retrieving these two components."

“Pulling an Image Manifest”.

, . : GET /v2/{name}/manifests/{reference}

"The name and reference parameter identify the image and are required. The reference may include a tag or digest."

, :

curl -s -X GET "http://localhost:8081/link/to/docker/registry/v2/centos-11-10/manifests/1.1.1" -H "header_if_needed"

json , . , : "GET /v2/{name}/blobs/{digest}"

“Access to a layer will be gated by the name of the repository but is identified uniquely in the registry by digest.”

digest , .

curl -s -X GET "http://localhost:8081/link/to/docker/registry/v2/centos-11-10/blobs/sha256:f972d139738dfcd1519fd2461815651336ee25a8b54c358834c50af094bb262f" -H "header_if_needed" --output firstLayer

.

file firstLayer

.. tar , .

#!/bin/bash -eu

downloadDir=$1
# url as http://localhost:8081/link/to/docker/registry
url=$2
imageName=$3
tag=$4

# array of layers
layers=($(curl -s -X GET "$url/v2/$imageName/manifests/$tag" | grep -oP '(?<=blobSum" : ").+(?=")'))

# download each layer from array
for layer in "${layers[@]}"; do
    echo "Downloading ${layer}"
    curl -v -X GET "$url/v2/$imageName/blobs/$layer" --output "$downloadDir/$layer.tar"
done

# find all layers, untar them and remove source .tar files
cd "$downloadDir" && find . -name "sha256:*" -exec tar xvf {} \;
rm sha256:*.tar
exit 0

./script.sh dirName “http://localhost:8081/link/to/docker/registry” myAwesomeImage 1.0

2 — docker push

.

. , . .

:

• — "POST /v2/{repoName}/blobs/uploads/"
• ( , .. ) — "PUT /v2/{repoName}/blobs/uploads/{uuid}?digest={digest}
  Content-Length: {size of layer}
  Content-Type: application/octet-stream
  Layer Binary Data".
• — "PUT /v2/{repoName}/manifests/{reference}".

, . (chunked) PATCH :

"PATCH /v2/{repoName}/blobs/uploads/{uuid}
Content-Length: {size of chunk}
Content-Type: application/octet-stream
{Layer Chunk Binary Data}".

, .. 202 4.

:

• 
  2 3 , .

. archlinux:latest

docker pull archlinux

docker save c24fe13d37b9 -o savedArch

tar xvf savedArch

. ,

cat manifest.json | json_pp

. , .

, .

config . 2 ( ), mediaType :

echo ‘{
   "schemaVersion": 2,
   "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
   "config": {
      "mediaType": "application/vnd.docker.container.image.v1+json",
      "size": config_size,
      "digest": "config_hash"
   },
   "layers": [
      ’ > manifest.json

. json :

{
         "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
         "size": ${layersSizes[$i]},
         "digest": \"sha256:${layersNames[$i]}\"
      },

.

sed -i "s/config_size/$configSize/g; s/config_hash/$configName/g" $manifestFile

Agora você pode iniciar o processo de inicialização e salvar o uuid, que deve ser acompanhado por todas as solicitações subsequentes.

O script completo é mais ou menos assim:

#!/bin/bash -eux

imageDir=$1
# url as http://localhost:8081/link/to/docker/registry
url=$2
repoName=$3
tag=$4
manifestFile=$(readlink -f ${imageDir}/manifestCopy)
configFile=$(readlink -f $(find $imageDir -name "*.json" ! -name "manifest.json"))

# calc layers sha 256 sum, rename them accordingly, and add info about each to manifest file
function prepareLayersForUpload() {
  info_file=$imageDir/info
  # lets calculate layers sha256 and use it as layers names further
  layersNames=($(find $imageDir -name "layer.tar" -exec shasum -a 256 {} \; | cut -d" " -f1))

  # rename layers according to shasums. !!!Set required amount of fields for cut command!!!
  # this part definitely can be done easier but i didn't found another way, sry
  find $imageDir -name "layer.tar" -exec bash -c 'mv {} "$(echo {} | cut -d"/" -f1,2)/$(shasum -a 256 {} | cut -d" " -f1)"' \;

  layersSizes=($(find $imageDir -name "*.tar" -exec ls -l {} \; | awk '{print $5}'))

  for i in "${!layersNames[@]}"; do
    echo "{
         "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
         "size": ${layersSizes[$i]},
         "digest": \"sha256:${layersNames[$i]}\"
      }," >> $manifestFile
  done
  # remove last ','
  truncate -s-2 $manifestFile
  # add closing brakets to keep json consistent
  printf "\n\t]\n}" >> $manifestFile
}

# calc config sha 256 sum and add info about it to manifest
function setConfigProps() {
  configSize=$(ls -l $configFile | awk '{print $5}')
  configName=$(basename $configFile | cut -d"." -f1)

  sed -i "s/config_size/$configSize/g; s/config_hash/$configName/g" $manifestFile
}

#prepare manifest file
prepareLayersForUpload
setConfigProps
cat $manifestFile

# initiate upload and get uuid
uuid=$(curl -s -X POST -I "$url/v2/$repoName/blobs/uploads/" | grep -oP "(?<=Docker-Upload-Uuid: ).+")

# patch layers
# in data-binary we're getting absolute path to layer file
for l in "${!layersNames[@]}"; do
  pathToLayer=$(find $imageDir -name ${layersNames[$l]} -exec readlink -f {} \;)
    curl -v -X PATCH "$url/v2/$repoName/blobs/uploads/$uuid" \
  -H "Content-Length: ${layersSizes[$i]}" \
  -H "Content-Type: application/octet-stream" \
  --data-binary "@$pathToLayer"

# put layer
  curl -v -X PUT "$url/v2/$repoName/blobs/uploads/$uuid?digest=sha256:${layersNames[$i]}" \
  -H 'Content-Type: application/octet-stream' \
  -H "Content-Length: ${layersSizes[$i]}" \
  --data-binary "@$pathToLayer"
done

# patch and put config after all layers
curl -v -X PATCH "$url/v2/$repoName/blobs/uploads/$uuid" \
  -H "Content-Length: $configSize" \
  -H "Content-Type: application/octet-stream" \
  --data-binary "@$configFile"

  curl -v -X PUT "$url/v2/$repoName/blobs/uploads/$uuid?digest=sha256:$configName" \
  -H 'Content-Type: application/octet-stream' \
  -H "Content-Length: $configSize" \
  --data-binary "@$configFile"

# put manifest
curl -v -X PUT "$url/v2/$repoName/manifests/$tag" \
  -H 'Content-Type: application/vnd.docker.distribution.manifest.v2+json' \
  --data-binary "@$manifestFile"

exit 0

podemos usar um script pronto:

./uploadImage.sh "~/path/to/saved/image" "http://localhost:8081/link/to/docker/registry" myRepoName 1.0

O artigo usou as ferramentas de versão GNU.

Em geral, o artigo não descobre os Estados Unidos, mas estrutura ligeiramente os dados díspares e suplementa as lacunas na documentação. Obrigado pela leitura.