AmazonLinuxでrubyからdocker apiを使う #Ruby

以前書いた AWSで初めてのDocker: AmazonLinux上でAmazonLinuxのコンテナを動かすの続き
AmazonLinuxのDockerホスト上でrubygemsのdocker-api(1.19.0)を使おうとしたところハマったのでその解決法を書きます

$ ruby -r docker -e 'p Docker.version'
/usr/local/share/ruby/gems/2.0/gems/docker-api-1.19.0/lib/docker/connection.rb:50:in `rescue in request': Expected([200, 201, 202, 203, 204, 304]) <=> Actual(404 Not Found) (Docker::Error::NotFoundError)
    from /usr/local/share/ruby/gems/2.0/gems/docker-api-1.19.0/lib/docker/connection.rb:38:in `request'
    from /usr/local/share/ruby/gems/2.0/gems/docker-api-1.19.0/lib/docker/connection.rb:61:in `block (2 levels) in <class:Connection>'
    from /usr/local/share/ruby/gems/2.0/gems/docker-api-1.19.0/lib/docker.rb:94:in `version'
    from -e:1:in `<main>'

結論

docker-apiの要求するのとDockerが提供するAPIのバージョンが違った

$ ruby -r docker -e 'Docker.validate_version!'
/usr/local/share/ruby/gems/2.0/gems/docker-api-1.19.0/lib/docker.rb:118:in `rescue in validate_version!': Expected API Version: 1.16 (Docker::Error::VersionError)
    from /usr/local/share/ruby/gems/2.0/gems/docker-api-1.19.0/lib/docker.rb:115:in `validate_version!'
    from -e:1:in `<main>'

$ curl http://localhost:4243/version
{"ApiVersion":"1.15","Arch":"amd64","GitCommit":"c78088f/1.3.3","GoVersion":"go1.3.3","KernelVersion":"3.14.27-25.47.amzn1.x86_64","Os":"linux","Version":"1.3.3"}

解決方法

現在のAmazonLinuxの最新でもAPI1.15なのでgemのバージョンを下げるしかない

$ gem install docker-api -v 1.18.0

$ ruby -r docker -e 'Docker.validate_version!; p Docker.version'
{"ApiVersion"=>"1.15", "Arch"=>"amd64", "GitCommit"=>"c78088f/1.3.3", "GoVersion"=>"go1.3.3", "KernelVersion"=>"3.14.27-25.47.amzn1.x86_64", "Os"=>"linux", "Version"=>"1.3.3"}