一文了解 Dockerfile 鲜为人知的一面
Hello folks，今天给大家介绍一下如何在 Dockerfile 中进行 Go 代码编写及运用（备注：此处暂不关注所部署的容器大小及性能问题）。现在，让我们准备测试应用程序，主要涉及 2 部分内容，具体包括：
1、一个简单的 HTTP 应用程序
2、一个类似 Sleep 的 CLI 工具
下面为一个完整的 Dockerfile 文件内容，如下所示：
# --- 此部定义构建相关内容 ---
FROM golang:1.18 as builder
WORKDIR /
COPY <<EOF server.go
# --- 此部分定义一个简单的 HTTP 程序 ---
package main
import (
"fmt"
"log"
"net/http"
)
func hello(w http.ResponseWriter, req *http.Request) {
fmt.Fprintf(w, "hello\\n")
}
func headers(w http.ResponseWriter, req *http.Request) {
for name, headers := range req.Header {
for _, h := range headers {
fmt.Fprintf(w, "%v: %v\\n", name, h)
}
}
}
func main() {
http.HandleFunc("/hello", hello)
http.HandleFunc("/headers", headers)
http.ListenAndServe(":8080", nil)
}
EOF
COPY <<EOF sleep.go
# --- 此部分定义一个简单的 Sleep cli 工具 ---
package main
import (
"log"
"time"
)
func main() {
for {
log.Println("What a fucking day !...")
time.Sleep(2 * time.Second)
}
}
EOF
RUN CGO_ENABLED=0 go build -o server server.go
RUN CGO_ENABLED=0 go build -o sleep sleep.go
# --- 此处定义一个简单的测试 Demo ---
FROM scratch
COPY --from=builder /server /server
COPY --from=builder /sleep /sleep
CMD ["/server"]
编写完 Dockerfile 后，我们尝试对其进行编译，看是否能够操作成功，具体步骤及输出如下所示：
[leonli@192 luga ] % docker buildx build -t fucking-day-app .
[+] Building 5.5s (17/17) FINISHED
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 1.17kB 0.0s
=> [internal] load .dockerignore 0.0s
=> => transferring context: 2B 0.0s
=> resolve image config for docker.io/docker/dockerfile:1.4 1.3s
=> CACHED docker-image://docker.io/docker/dockerfile:1.4@sha256:91f386bc3ae6cd5585fbd02f811e295b4a7020c23c7691d686830bf6233e91ad 0.0s
=> [internal] load .dockerignore 0.0s
=> [internal] load build definition from Dockerfile 0.0s
=> [internal] load metadata for docker.io/library/golang:1.18 1.2s
=> [internal] preparing inline document 0.0s
=> CACHED [builder 1/6] FROM docker.io/library/golang:1.18@sha256:12d3995156cb0dcdbb9d3edb5827e4e8e1bf5bf92436bfd12d696ec997001a9a 0.0s
=> CACHED [internal] preparing inline document 0.0s
=> [builder 2/6] COPY <<EOF server.go 0.0s
=> [builder 3/6] COPY <<EOF sleep.go 0.0s
=> [builder 4/6] RUN CGO_ENABLED=0 go build -o server server.go 1.8s
=> [builder 5/6] RUN CGO_ENABLED=0 go build -o sleep sleep.go 0.3s
=> [stage-1 1/2] COPY --from=builder /server /server 0.0s
=> [stage-1 2/2] COPY --from=builder /sleep /sleep 0.0s
=> exporting to image 0.0s
=> => exporting layers 0.0s
=> => writing image sha256:3b0654a3f178886aebfecc7ec85b87861acf124a2776948686df5fda7a2b4577 0.0s
=> => naming to docker.io/library/fucking-day-app 基于上述的输出 信息 ，我们发现没有异常信息抛出，貌似一切都很顺利。接下来，我们通过命令行查看一下所创建的 Image 文件，具体如下所示：
[leonli@192 luga ] % docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
fucking-day-app latest 3b0654a3f178 54 seconds ago 7.85MB
registry 2 c776ad7009a1 6 weeks ago 22.6MB
rancher/k3d-tools 5.3.0 30d7dcea1d69 3 months ago 18.2MB
rancher/k3d-proxy 5.3.0 0fec4b02df22 3 months ago 39.7MB
rancher/k3s v1.22.6-k3s1 ee6507fdfdfe 3 months ago 155MB可以看到，此时 Image 文件 已成功生成，然后，我们创建一个命名为 “fucking-day-app” 的容器并将其运行，具体如下：
[leonli@192 luga ] % docker create --name fucking-day-app fucking-day-app
d9903f249897dadadb7e80cf0ac539b8d71abcd421c5b5f22a4d7a72c44d6f4e
[leonli@192 luga ] % docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d9903f249897 fucking-day-app "/server" 5 seconds ago Created fucking-day-app
56ce21236c38 rancher/k3d-proxy:5.3.0 "/bin/sh -c nginx-pr…" 4 weeks ago Exited (137) 2 weeks ago k3d-devops-cluster-serverlb
47f510e0045c rancher/k3s:v1.22.6-k3s1 "/bin/k3d-entrypoint…" 4 weeks ago Exited (0) 2 weeks ago k3d-devops-cluster-agent-1
8b2010a8f994 rancher/k3s:v1.22.6-k3s1 "/bin/k3d-entrypoint…" 4 weeks ago Exited (0) 2 weeks ago k3d-devops-cluster-agent-0
211d105c1d88 rancher/k3s:v1.22.6-k3s1 "/bin/k3d-entrypoint…" 4 weeks ago Exited (0) 2 weeks ago k3d-devops-cluster-server-0[leonli@192 luga ] % docker start d9903f249897
d9903f249897
leonli@192 luga % docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d9903f249897 fucking-day-app "/server" 38 seconds ago Up 2 seconds fucking-day-app
c1d43fad83d0 fucking-app "/server" 6 hours ago Up 6 hours fucking-app
截止到此处，fucking-day-app 容器已正常启动，我们来看一下其后台日志，以验证是否存在异常错误，具体如下所示：
[leonli@192 luga ] % docker logs -f d9903f249897
2022/05/06 14:03:38 Starting HTTP server...
接下来，我们基于 Dockerfile 文件中所定义的测试 Demo 进行验证，按理来说，其应该正常会输出：“ What a fucking day !... ” 相关内容， 如下所示：
[leonli@192 luga ] % docker exec -it fucking-day-app /sleep
2022/05/06 14:04:45 What a fucking day !...
2022/05/06 14:04:47 What a fucking day !...
2022/05/06 14:04:49 What a fucking day !...
2022/05/06 14:04:51 What a fucking day !...
2022/05/06 14:04:53 What a fucking day !...
2022/05/06 14:04:55 What a fucking day !...
2022/05/06 14:04:57 What a fucking day !...
2022/05/06 14:04:59 What a fucking day !...
2022/05/06 14:05:01 What a fucking day !...
2022/05/06 14:05:03 What a fucking day !...
2022/05/06 14:05:05 What a fucking day !...
2022/05/06 14:05:07 What a fucking day !...
2022/05/06 14:05:09 What a fucking day !...
2022/05/06 14:05:11 What a fucking day !...
2022/05/06 14:05:13 What a fucking day !...
2022/05/06 14:05:15 What a fucking day !...
2022/05/06 14:05:17 What a fucking day !...
2022/05/06 14:05:19 What a fucking day !...
2022/05/06 14:05:21 What a fucking day !...
2022/05/06 14:05:23 What a fucking day !...
2022/05/06 14:05:25 What a fucking day !...
2022/05/06 14:05:27 What a fucking day !...与 Dockerfile 文件中所定义的内容一致，每间隔 2 s 输出 “What a fucking day !...” 相关内容。至此，一个简单的 Demo 先解析到此为止，希望大家有所收获！
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