Cloud Native Buildpacks Tutorial - 2.4. ┗ gcr.io/paketo-buildpacks/builder:base BuilderでGolangアプリのOCIイメージを作成

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gcr.io/paketo-buildpacks/builder:baseでGolangのアプリケーションのOCIイメージを作成します。

BuilderとStackを予めpullしておいてください。

docker pull gcr.io/paketo-buildpacks/builder:base
docker pull gcr.io/paketo-buildpacks/run:base-cnb

次のコマンドで"Hello World"アプリケーションを作成します。

cd ${GOPATH}/src
mkdir -p github.com/making/hello-golang
cd github.com/making/hello-golang
go mod init

cat <<'EOF' > main.go
package main

import (
  "fmt"
  "net/http"
)

func main() {
  http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
    fmt.Fprint(w, "Hello World!")
  })
  http.ListenAndServe(":8080", nil)
}
EOF

pack buildコマンドでイメージを作成します。

pack build making/pack-golang --no-pull --builder gcr.io/paketo-buildpacks/builder:base

BuilderとStackを事前にpullしていない場合は--no-pullを外せば、ビルド時にBuilderとStackもpullしますが、ビルドが遅くなります。

次のようなログが出力されます。

===> DETECTING
[detector] paketo-buildpacks/go-compiler 0.0.112
[detector] paketo-buildpacks/go-mod      0.0.96
===> ANALYZING
[analyzer] Previous image with name "index.docker.io/making/pack-golang:latest" not found
===> RESTORING
===> BUILDING
[builder] 
[builder] Go Compiler Buildpack 0.0.112
[builder]   Go 1.13.9: Contributing to layer
[builder]     Downloading from https://buildpacks.cloudfoundry.org/dependencies/go/go-1.13.9-bionic-61a279e8.tgz
[builder]     Verifying checksum
[builder]     Expanding to /layers/paketo-buildpacks_go-compiler/go
[builder] 
[builder] Go Mod Buildpack 0.0.96
[builder] Setting environment variables
[builder]   : Contributing to layer
[builder] github.com/making/hello-golang
[builder]   : Contributing to layer
[builder] Running `go install`
[builder]   : Contributing to layer
[builder] Contributing start command
[builder]   Process types:
[builder]     web: /layers/paketo-buildpacks_go-mod/app-binary/bin/hello-golang
===> EXPORTING
[exporter] Adding layer 'launcher'
[exporter] Adding layer 'paketo-buildpacks/go-mod:app-binary'
[exporter] Adding 1/1 app layer(s)
[exporter] Adding layer 'config'
[exporter] *** Images (d8970e079210):
[exporter]       index.docker.io/making/pack-golang:latest
[exporter] Adding cache layer 'paketo-buildpacks/go-compiler:61a279e80c8d3a03ae9464dc2fc263e37e0655d45e9931693ea9522bfbb91847'
[exporter] Adding cache layer 'paketo-buildpacks/go-compiler:go'
[exporter] Adding cache layer 'paketo-buildpacks/go-mod:go-cache'
[exporter] Adding cache layer 'paketo-buildpacks/go-mod:go-mod'
Successfully built image making/pack-golang

pack build時に--publishオプションをつけると、Docker Registryでのpushを行います。事前にdocker loginが必要です。

作成したイメージをdocker runで起動します。

docker run --rm -p 8080:8080 making/pack-golang

アプリケーションにアクセスします。

$ curl localhost:8080 -w '\n'
Hello World!

Docker Imageのサイズを確認します。

$ docker images | grep making/pack-golang
making/pack-golang                   latest              d8970e079210        40 years ago        82.8MB

pack inspect-imageでイメージを解析します。

$ pack inspect-image making/pack-golang
Inspecting image: making/pack-golang

REMOTE:
(not present)

LOCAL:

Stack: io.buildpacks.stacks.bionic

Base Image:
  Reference: 40845d52d6fb6d285a320aeac821b61cff0e2863e0ff12e12138c4775aae1828
  Top Layer: sha256:f0d87426c0a82340475d73a9108b063d3d3cfbd92ef3b4af74dcd8f904475a36

Run Images:
  gcr.io/paketo-buildpacks/run:base-cnb

Buildpacks:
  ID                                   VERSION
  paketo-buildpacks/go-compiler        0.0.112
  paketo-buildpacks/go-mod             0.0.96

Processes:
  TYPE                 SHELL        COMMAND                                                             ARGS
  web (default)        bash         /layers/paketo-buildpacks_go-mod/app-binary/bin/hello-golang

Golang Buildpackの細かい設定は https://github.com/paketo-buildpacks/go を確認してください。

おわったらDocker Imageを削除します。

docker rmi making/pack-golang