Bundle to manage docker images

[neilhwatson]

Keep docker images current by checking existing images and build new ones from Dockerfiles if current ones are old or missing.

Getting info from Docker API

1. Get creation time of image with given RepoTag:
   curl -s --unix-socket /run/docker.sock http://docker/images/json|jq '.[] | select( .RepoTags[] == "my_tag:latest" )|.Created''

Compare time against Dockerfile and support files' ctime. Invoke new build if Created is older.

[neilhwatson]

Prototype

Assumptions

1. Dockerfile and other support files have been staged by another bundle.
2. We pole the agent host's Docker api via socket, not remote.
3. Docker service is installed and running on agent host.

Code

body common control
{
    bundlesequence => { "main", };
}

bundle agent main
{
    methods:

        "any" usebundle => docker_images;
}

bundle agent docker_images 
{
   vars:
      "images_wanted"
         comment => "Sample data, would normally be a passed in param file",
         data    => parsejson( '
            [
               {
                  docker_dir: "/home/neil/src/neil/cfbot"
                  Tag:         "cfbot",
                  RepoTags:    "cfbot:latest",
               }
            ]'
         );

      "i" slist => getindices( "images_wanted" );

   methods:

      "${i}"
         comment   => "Pass do another bunle for simpler iteration",
         usebundle => promise_docker_image( @{images_wanted}, ${i} );

}

bundle agent promise_docker_image ( images_wanted, i )
{
   vars:

      "image"
         comment => "Get image info from docker api for the given tag",
         data    => parsejson(
            execresult( 

            "/usr/bin/curl --silent \
               --unix-socket /run/docker.sock http://docker/images/json \
               | jq '.[] | select( .RepoTags[] \
               == \"${images_wanted[${i}][RepoTags]}\" )|.'",

            "useshell" )
            );

      "docker_files"
         comment => "Get list of given docker files",
         slist   =>
            splitstring(
               execresult(
                  "/usr/bin/find ${images_wanted[${i}][docker_dir]} -type f"
                  , "noshell"
               ),
               "\n", "999"
            );

   classes:
      "build_docker_image_${i}_${images_wanted[${i}][RepoTags]}"
         comment    => "Test if any related docker file is newer",
         expression =>
            isgreaterthan(
               filestat( "${docker_files}", mtime ), ${image[Created]}
            );

   reports:
      "docker build -t ${images_wanted[${i}][Tag]} ."
         comment => "Here we would force a rebuild of the docker image",
         # contain => usedir( "${images_wnated[${i}][docker_dir]}" ),
         if      => canonify( 
                       "build_docker_image_${i}_${images_wanted[${i}][RepoTags]}"
                    ); 
}