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导读

在容器化实践中部署spring boot应用普遍采用基础java镜像再添加jar包层来构建应用镜像制品。随着公司业务大量上云，每个变更日上传到云上镜像日渐增多，导致本地机房到云上带宽压力倍增。为解决镜像上传问题，调研了相关技术栈决定采用spring boot 2.3新增的镜像分层构建功能。

基础环境

spring boot version >= 2.3
java oracle jdk 8u201
docker version 20.10.13

基于传统单个jar包构建模式

基础Dockerfile

以下是我们基于基础镜像构建spring boot镜像制品的Dockerfile，采用了比较传统的COPY jar包。相信这也是大家普遍采用的模式。Dockefile如下，该Dockerfile存在一个坑，会在下边阐述。

FROM registry.xxx.com/base/oracle-jdk:8u201
ENV TZ=Asia/Shanghai
ENV LC_ALL en_US.utf8
WORKDIR /app
ADD ./xxx-1.0.0.jar /app/lib/xxx-1.0.0.jar
ADD ./entrypoint.sh /app/bin/entrypoint.sh
ENTRYPOINT  exec bash /app/bin/entrypoint.sh
RUN ln -s /app/logs /app/log && chown 1001.1001 -R /app

Base镜像信息

我们base镜像主要分三层添加了相关常用的工具如telnet netstat等以及安全修复

docker image inspect registry.xxx.com/base/oracle-jdk:8u201

分层信息：

"RootFS": {
    "Type": "layers",
    "Layers": [
        "sha256:174f5685490326fc0a1c0f5570b8663732189b327007e47ff13d2ca59673db02",
        "sha256:2105884a1756425b2188084cc1738d6a6b13293773af56f6727af1be979858ed",
        "sha256:c33745b350978d855171c996779055195b09e227844b7a03a1d795aee803dbb9"
    ]
}

Base镜像大小 622MB

镜像大小 622MB 不算太小，对比友商有些基础镜像竟然1-2G😂 简直有点离谱。

registry.xxx.com/base/oracle-jdk  8u201 1869b73a8999  2 years ago  622MB

Base镜像history信息

从构建历史可以看出占用空间主要分为三层分别是

centos 7 基础镜像层
yum install 层
jdk 层

docker image  history registry.xxx.com/base/oracle-jdk:8u201
IMAGE          CREATED       CREATED BY                                      SIZE      COMMENT
1869b73a8999   2 years ago   /bin/sh -c set -ex;   cd /tmp;   curl -fsSLO…   302MB
<missing>      2 years ago   /bin/sh -c #(nop)  ENV JAVA_VERSION=8 JAVA_U…   0B
<missing>      2 years ago   /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai LANG…   0B
<missing>      2 years ago   /bin/sh -c set -ex;   yum update -y;   yum i…   116MB
<missing>      2 years ago   /bin/sh -c #(nop)  LABEL maintainer=…           0B
<missing>      2 years ago   /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B
<missing>      2 years ago   /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B
<missing>      2 years ago   /bin/sh -c #(nop) ADD file:b3ebbe8bd304723d4…   204MB

传统构建方式

docker build -t registry.xxx.com/layer/build:old .
Sending build context to Docker daemon  67.45MB
Step 1/8 : FROM registry.xxx.com/base/oracle-jdk:8u201
 ---> 1869b73a8999
Step 2/8 : ENV TZ=Asia/Shanghai
 ---> Running in a67423d7246b
Removing intermediate container a67423d7246b
 ---> 9304102c278e
Step 3/8 : ENV LC_ALL en_US.utf8
 ---> Running in 05bf14c10efd
Removing intermediate container 05bf14c10efd
 ---> 63fb6c823893
Step 4/8 : WORKDIR /app
 ---> Running in 095764328d18
Removing intermediate container 095764328d18
 ---> c057ab4a7d18
Step 5/8 : ADD ./xxx-1.0.0.jar /app/lib/xxx-1.0.0.jar
 ---> 08928447fafa
Step 6/8 : ADD ./entrypoint.sh /app/bin/entrypoint.sh
 ---> 0902efa62157
Step 7/8 : ENTRYPOINT  exec bash /app/bin/entrypoint.sh
 ---> Running in dc0eb814cfff
Removing intermediate container dc0eb814cfff
 ---> 20679a170252
Step 8/8 : RUN ln -s /app/logs /app/log && chown 1001.1001 -R /app
 ---> Running in 34159dca7464
Removing intermediate container 34159dca7464
 ---> b6043465c072
Successfully built b6043465c072
Successfully tagged registry.xxx.com/layer/build:old

构建后镜像大小为基础镜像大小 622MB + 2*65M <= 757MB

构建后比我们预期的 jar包加基础镜像所占用的空间大😢 why?

#jar包大小
ls -lh xxx-1.0.0.jar
-rw------- 1 root root 65M Aug 16 10:33 xxx-1.0.0.jar

#镜像大小
docker image ls |grep registry.xxx.com/layer/build
registry.xxx.com/layer/build                 old          b6043465c072   59 seconds ago   757MB

成品构建history信息

查看构建成品的镜像层发现竟然有两层一样大小，也会被推送了两遍。🥲离大谱。通过分析Dockerfile是因为RUN ln -s /app/logs /app/log && chown 1001.1001 -R /app 导致的。为保证镜像安全，生产环境运行统一采用了1001账号运行。为了保证1001对workdir有绝对的读写权限。对目录递归授权导致文件属性发生改变。

在构建时认为文件发生变化产生一样大小的两层导致的。（这还是我自己当时优化引入的屎山😊）具体原因我也不太清楚docker构建时如何判定文件发生变化，我原本以为是基于MD5码。实际上在对文件属主属组改变时MD5码是不对变的。有知道的大神可以在评论区留言交流。

docker image  history  registry.xxx.com/layer/build:old
IMAGE          CREATED         CREATED BY                                      SIZE      COMMENT
b6043465c072   6 minutes ago   /bin/sh -c ln -s /app/logs /app/log && chown…   67.4MB
20679a170252   6 minutes ago   /bin/sh -c #(nop)  ENTRYPOINT ["/bin/sh" "-c…   0B
0902efa62157   6 minutes ago   /bin/sh -c #(nop) ADD file:9ac19caf793524884…   128B
08928447fafa   6 minutes ago   /bin/sh -c #(nop) ADD file:c7624c195e7c047ee…   67.4MB
c057ab4a7d18   6 minutes ago   /bin/sh -c #(nop) WORKDIR /app                  0B
63fb6c823893   6 minutes ago   /bin/sh -c #(nop)  ENV LC_ALL=en_US.utf8        0B
9304102c278e   6 minutes ago   /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai         0B
1869b73a8999   2 years ago     /bin/sh -c set -ex;   cd /tmp;   curl -fsSLO…   302MB
<missing>      2 years ago     /bin/sh -c #(nop)  ENV JAVA_VERSION=8 JAVA_U…   0B
<missing>      2 years ago     /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai LANG…   0B
<missing>      2 years ago     /bin/sh -c set -ex;   yum update -y;   yum i…   116MB
<missing>      2 years ago     /bin/sh -c #(nop)  LABEL maintainer=currycan…   0B
<missing>      2 years ago     /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B
<missing>      2 years ago     /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B
<missing>      2 years ago     /bin/sh -c #(nop) ADD file:b3ebbe8bd304723d4…   204MB

#镜像也推送了两层一样大小
[root@localhost old-nochown]# docker push registry.xxx.com/layer/build:old
The push refers to repository [registry.xxx.com/layer/build]
bb35157fcb0b: Pushing [=============>                                     ]  18.35MB/67.45MB
3c0641004863: Pushed
6ed0abaff975: Pushing [=====================>                             ]  28.38MB/67.45MB
aa0794231b2c: Pushed
c33745b35097: Layer already exists
2105884a1756: Layer already exists
174f56854903: Layer already exists

优化Dockerfile

原因知道了。优化思路是先创建目录并递归授权。同时构建出来的jar的权限可以通过COPY 指定1001属主属组。

FROM registry.xxx.com/base/oracle-jdk:8u201
ENV TZ=Asia/Shanghai
ENV LC_ALL en_US.utf8
RUN mkdir -pv /app/{bin,lib,logs} && ln -s /app/logs /app/log && chown 1001:1001 -R /app
WORKDIR /app
COPY  --chown=1001:1001 ./xxx-1.0.0.jar /app/lib/xxx-1.0.0.jar
COPY  --chown=1001:1001 ./entrypoint.sh /app/bin/entrypoint.sh
ENTRYPOINT  exec bash /app/bin/entrypoint.sh

优化后的镜像只有COPY这一层的jar包了。

docker image history registry.xxx.com/layer/build:old-mkdir
IMAGE          CREATED        CREATED BY                                      SIZE      COMMENT
b9fc3a8a97f2   29 hours ago   /bin/sh -c #(nop)  ENTRYPOINT ["/bin/sh" "-c…   0B
c823448f9582   29 hours ago   /bin/sh -c #(nop) COPY --chown=1001:1001file…   128B
9a997f3962bf   29 hours ago   /bin/sh -c #(nop) COPY --chown=1001:1001file…   67.4MB
f272c4e64f87   29 hours ago   /bin/sh -c #(nop) WORKDIR /app                  0B
1a526d3df7c2   29 hours ago   /bin/sh -c mkdir -pv /app/{bin,lib,logs} && …   9B
63fb6c823893   30 hours ago   /bin/sh -c #(nop)  ENV LC_ALL=en_US.utf8        0B
9304102c278e   30 hours ago   /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai         0B
1869b73a8999   2 years ago    /bin/sh -c set -ex;   cd /tmp;   curl -fsSLO…   302MB
<missing>      2 years ago    /bin/sh -c #(nop)  ENV JAVA_VERSION=8 JAVA_U…   0B
<missing>      2 years ago    /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai LANG…   0B
<missing>      2 years ago    /bin/sh -c set -ex;   yum update -y;   yum i…   116MB
<missing>      2 years ago    /bin/sh -c #(nop)  LABEL maintainer=currycan…   0B
<missing>      2 years ago    /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B
<missing>      2 years ago    /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B
<missing>      2 years ago    /bin/sh -c #(nop) ADD file:b3ebbe8bd304723d4…   204MB

基于spring boot 分层构建方式

探索基于分层构建原理

直接上手官方文档的demo 把官方文档demo的多阶段构建拆分一下。

cat Dockerfile
FROM registry.xxx.com/base/oracle-jdk:8u201 as builder
WORKDIR /app
COPY --chown=1001:1001 ./xxx-1.0.0.jar /app/lib/xxx-1.0.0.jar
RUN java -Djarmode=layertools -jar /app/lib/xxx-1.0.0.jar extract

一阶段实际就是将jar解压按照spring boot layers.idx文件中的分层方式将依赖和业务代码分层。

- "dependencies":
  - BOOT-INF/lib/library1.jar
  - BOOT-INF/lib/library2.jar
- "spring-boot-loader":
  - org/springframework/boot/loader/JarLauncher.class
  - org/springframework/boot/loader/jar/JarEntry.class
- "snapshot-dependencies":
  - BOOT-INF/lib/library3-SNAPSHOT.jar
- "application":
  - META-INF/MANIFEST.MF
  - BOOT-INF/classes/a/b/C.class

进入到容器中可以看到被解压为4个目录：

[root@b762a63589c1 app]# ls
application  dependencies  lib  logs  snapshot-dependencies  spring-boot-loader

存储占用如下：其中不出意外dependencies也就是依赖库占用是最大的业务代码只有可怜的304K🤔。

[root@29d87aaf64b9 app]# du -lh  --max-depth=1
304K    ./application
65M     ./dependencies
0       ./logs
20K     ./snapshot-dependencies
420K    ./spring-boot-loader
65M     ./lib
130M    .

基于分层构建构建制品镜像

在官方的demo上修改得到完整的Dockerfile。其中优化了entrypoint脚本，采用分层构建后启动应用不能采用传统的java $JAVA_OPTS -jar xxx.jar这方式启动应用。要使用java org.springframework.boot.loader.JarLauncher启动应用因此jvm参数需要通过脚本接受容器的环境变量来传入。

FROM registry.xxx.com/base/oracle-jdk:8u201 as builder
WORKDIR /app
COPY --chown=1001:1001 ./xxx-1.0.0.jar /app/lib/xxx-1.0.0.jar
RUN java -Djarmode=layertools -jar /app/lib/xxx-1.0.0.jar extract

FROM registry.xxx.com/base/oracle-jdk:8u201
ENV TZ=Asia/Shanghai
ENV LC_ALL en_US.utf8
RUN mkdir -pv /app/logs && ln -s /app/logs /app/log && chown 1001:1001 -R /app
WORKDIR /app
COPY --chown=1001:1001 --from=builder /app/dependencies/ ./
COPY --chown=1001:1001 --from=builder /app/spring-boot-loader/ ./
COPY --chown=1001:1001 --from=builder /app/snapshot-dependencies/ ./
COPY --chown=1001:1001 --from=builder /app/application/ ./
CMD ["exec"]
ENTRYPOINT ["bash","/app/entrypoint.sh"]

entrypoint.sh脚本使用exec将java作为容器1号进程，避免无法接受linux 信号导致java进程无法正常退出。

#!/bin/bash
if [ -f /opt/cm/before.sh ]; then
source /opt/cm/before.sh;
fi
exec java $JAVA_OPTS org.springframework.boot.loader.JarLauncher

构建镜像

[root@localhost new]# docker build -t registry.xxx.com/layer/build:new .
Sending build context to Docker daemon  67.45MB
Step 1/14 : FROM registry.xxx.com/base/oracle-jdk:8u201 as builder
 ---> 1869b73a8999
Step 2/14 : WORKDIR /app
 ---> Using cache
 ---> 6973e49f31fa
Step 3/14 : COPY --chown=1001:1001 ./xxx-1.0.0.jar /app/lib/xxx-1.0.0.jar
 ---> Using cache
 ---> c5a17d5969ea
Step 4/14 : RUN java -Djarmode=layertools -jar /app/lib/xxx-1.0.0.jar extract
 ---> Using cache
 ---> 911074c3ef21
Step 5/14 : FROM registry.xxx.com/base/oracle-jdk:8u201
 ---> 1869b73a8999
Step 6/14 : ENV TZ=Asia/Shanghai
 ---> Using cache
 ---> 9304102c278e
Step 7/14 : ENV LC_ALL en_US.utf8
 ---> Using cache
 ---> 63fb6c823893
Step 8/14 : RUN mkdir -pv /app/logs && ln -s /app/logs /app/log && chown 1001:1001 -R /app
 ---> Running in 9cac9cb86507
mkdir: created directory ‘/app’
mkdir: created directory ‘/app/logs’
Removing intermediate container 9cac9cb86507
 ---> 858e77315e6b
Step 9/14 : WORKDIR /app
 ---> Running in 81c7173692fc
Removing intermediate container 81c7173692fc
 ---> 5c19ddda3114
Step 10/14 : COPY --chown=1001:1001 --from=builder /app/dependencies/ ./
 ---> 078e3f4a199c
Step 11/14 : COPY --chown=1001:1001 --from=builder /app/spring-boot-loader/ ./
 ---> 1542209ccc8b
Step 12/14 : COPY --chown=1001:1001 --from=builder /app/snapshot-dependencies/ ./
 ---> 75a9584e0952
Step 13/14 : COPY --chown=1001:1001 --from=builder /app/application/ ./
 ---> 555270edceea
Step 14/14 : ENTRYPOINT ["java", "org.springframework.boot.loader.JarLauncher"]
 ---> Running in fe99278683a2
Removing intermediate container fe99278683a2
 ---> 2cce0deab7e2
Successfully built 2cce0deab7e2
Successfully tagged registry.xxx.com/layer/build:new

查看分层详情，可以看到jar被拆分成4层分别由copy指令创建。

[root@localhost ~]# docker image history registry.xxx.com/layer/build:new
IMAGE          CREATED        CREATED BY                                      SIZE      COMMENT
2cce0deab7e2   28 hours ago   /bin/sh -c #(nop)  ENTRYPOINT ["java" "org.s…   0B
555270edceea   28 hours ago   /bin/sh -c #(nop) COPY dir:2f5975d11563ae449…   248kB
75a9584e0952   28 hours ago   /bin/sh -c #(nop) COPY dir:a3bb0870001a0ef25…   18.5kB
1542209ccc8b   28 hours ago   /bin/sh -c #(nop) COPY dir:16d00ea1f180914e2…   252kB
078e3f4a199c   28 hours ago   /bin/sh -c #(nop) COPY dir:1d3190ed598b634a5…   67.1MB
5c19ddda3114   28 hours ago   /bin/sh -c #(nop) WORKDIR /app                  0B
858e77315e6b   28 hours ago   /bin/sh -c mkdir -pv /app/logs && ln -s /app…   9B
63fb6c823893   30 hours ago   /bin/sh -c #(nop)  ENV LC_ALL=en_US.utf8        0B
9304102c278e   30 hours ago   /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai         0B
1869b73a8999   2 years ago    /bin/sh -c set -ex;   cd /tmp;   curl -fsSLO…   302MB
<missing>      2 years ago    /bin/sh -c #(nop)  ENV JAVA_VERSION=8 JAVA_U…   0B
<missing>      2 years ago    /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai LANG…   0B
<missing>      2 years ago    /bin/sh -c set -ex;   yum update -y;   yum i…   116MB
<missing>      2 years ago    /bin/sh -c #(nop)  LABEL maintainer=currycan…   0B
<missing>      2 years ago    /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B
<missing>      2 years ago    /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B
<missing>      2 years ago    /bin/sh -c #(nop) ADD file:b3ebbe8bd304723d4…   204MB

对比发现jar包被拆分了。

[root@localhost new]# diff old.info  new.info
1,16c1,18
< IMAGE          CREATED             CREATED BY                                      SIZE      COMMENT
< b9fc3a8a97f2   About an hour ago   /bin/sh -c #(nop)  ENTRYPOINT ["/bin/sh" "-c…   0B
< c823448f9582   About an hour ago   /bin/sh -c #(nop) COPY --chown=1001:1001file…   128B
< 9a997f3962bf   About an hour ago   /bin/sh -c #(nop) COPY --chown=1001:1001file…   67.4MB
< f272c4e64f87   About an hour ago   /bin/sh -c #(nop) WORKDIR /app                  0B
< 1a526d3df7c2   About an hour ago   /bin/sh -c mkdir -pv /app/{bin,lib,logs} && …   9B
< 63fb6c823893   2 hours ago         /bin/sh -c #(nop)  ENV LC_ALL=en_US.utf8        0B
< 9304102c278e   2 hours ago         /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai         0B
< 1869b73a8999   2 years ago         /bin/sh -c set -ex;   cd /tmp;   curl -fsSLO…   302MB
< <missing>      2 years ago         /bin/sh -c #(nop)  ENV JAVA_VERSION=8 JAVA_U…   0B
< <missing>      2 years ago         /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai LANG…   0B
< <missing>      2 years ago         /bin/sh -c set -ex;   yum update -y;   yum i…   116MB
< <missing>      2 years ago         /bin/sh -c #(nop)  LABEL maintainer=currycan…   0B
< <missing>      2 years ago         /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B
< <missing>      2 years ago         /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B
< <missing>      2 years ago         /bin/sh -c #(nop) ADD file:b3ebbe8bd304723d4…   204MB
---
> IMAGE          CREATED         CREATED BY                                      SIZE      COMMENT
> 2cce0deab7e2   8 minutes ago   /bin/sh -c #(nop)  ENTRYPOINT ["java" "org.s…   0B
> 555270edceea   8 minutes ago   /bin/sh -c #(nop) COPY dir:2f5975d11563ae449…   248kB
> 75a9584e0952   8 minutes ago   /bin/sh -c #(nop) COPY dir:a3bb0870001a0ef25…   18.5kB
> 1542209ccc8b   8 minutes ago   /bin/sh -c #(nop) COPY dir:16d00ea1f180914e2…   252kB
> 078e3f4a199c   8 minutes ago   /bin/sh -c #(nop) COPY dir:1d3190ed598b634a5…   67.1MB
> 5c19ddda3114   8 minutes ago   /bin/sh -c #(nop) WORKDIR /app                  0B
> 858e77315e6b   8 minutes ago   /bin/sh -c mkdir -pv /app/logs && ln -s /app…   9B
> 63fb6c823893   2 hours ago     /bin/sh -c #(nop)  ENV LC_ALL=en_US.utf8        0B
> 9304102c278e   2 hours ago     /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai         0B
> 1869b73a8999   2 years ago     /bin/sh -c set -ex;   cd /tmp;   curl -fsSLO…   302MB
> <missing>      2 years ago     /bin/sh -c #(nop)  ENV JAVA_VERSION=8 JAVA_U…   0B
> <missing>      2 years ago     /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai LANG…   0B
> <missing>      2 years ago     /bin/sh -c set -ex;   yum update -y;   yum i…   116MB
> <missing>      2 years ago     /bin/sh -c #(nop)  LABEL maintainer=currycan…   0B
> <missing>      2 years ago     /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B
> <missing>      2 years ago     /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B
> <missing>      2 years ago     /bin/sh -c #(nop) ADD file:b3ebbe8bd304723d4…   204MB

推送到仓库

[root@localhost new]# docker push registry.xxx.com/layer/build:new
The push refers to repository [registry.xxx.com/layer/build]
e5409ea62302: Pushed
7167dfa406ea: Pushed
cf7e94a2dc11: Pushed
8e261e1bae2c: Pushed
770c31a84800: Pushed
c33745b35097: Layer already exists
2105884a1756: Layer already exists
174f56854903: Layer already exists
new: digest: sha256:faef10681394c01d1c2973ed10c7c33e7289eec25f22c90d085f6eef96ce3bff size: 2001

验证模拟开发推送代码更新镜像

开发摸了一天🐟终于开发出新版本

[root@localhost new]# md5sum  bc-1.0.1.jar  bc-1.0.0.jar
3792d3178a4e07708052b7effa9b12f8  xxx-1.0.1.jar
8ee570b94977668631355cb49c5d7cf1  xxx-1.0.0.jar

构建新版本，构建过程阶段二中使用了cache 仅更新了 application层

[root@localhost new]# docker image build -t  registry.xxx.com/layer/build:new-1.0.1 .
Sending build context to Docker daemon  134.9MB
Step 1/16 : FROM registry.xxx.com/base/oracle-jdk:8u201 as builder
 ---> 1869b73a8999
Step 2/16 : WORKDIR /app
 ---> Using cache
 ---> 6973e49f31fa
Step 3/16 : COPY --chown=1001:1001 ./xxx-1.0.1.jar /app/lib/xxx-1.0.1.jar
 ---> b219210fd8ab
Step 4/16 : RUN java -Djarmode=layertools -jar /app/lib/xxx-1.0.1.jar extract
 ---> Running in d099c10b653c
Removing intermediate container d099c10b653c
 ---> 66a8593b0291
Step 5/16 : FROM registry.xxx.com/base/oracle-jdk:8u201
 ---> 1869b73a8999
Step 6/16 : ENV TZ=Asia/Shanghai
 ---> Using cache
 ---> 9304102c278e
Step 7/16 : ENV LC_ALL en_US.utf8
 ---> Using cache
 ---> 63fb6c823893
Step 8/16 : RUN mkdir -pv /app/logs && ln -s /app/logs /app/log && chown 1001:1001 -R /app
 ---> Using cache
 ---> 858e77315e6b
Step 9/16 : WORKDIR /app
 ---> Using cache
 ---> 5c19ddda3114
 Step 10/16 : COPY --chown=1001:1001 ./entrypoint.sh /app/entrypoint.sh
 ---> Using cache
 ---> c47b74bb8cf9
Step 11/16 : COPY --chown=1001:1001 --from=builder /app/dependencies/ ./
 ---> Using cache
 ---> 078e3f4a199c
Step 12/16 : COPY --chown=1001:1001 --from=builder /app/spring-boot-loader/ ./
 ---> Using cache
 ---> 1542209ccc8b
Step 13/16 : COPY --chown=1001:1001 --from=builder /app/snapshot-dependencies/ ./
 ---> Using cache
 ---> 75a9584e0952
Step 14/16 : COPY --chown=1001:1001 --from=builder /app/application/ ./
 ---> 0f138b106caf
Step 15/16 : CMD ["exec"]
 ---> Using cache
 ---> a1170ae7a20e
Step 16/16 : ENTRYPOINT ["bash","/app/entrypoint.sh"]
 ---> Using cache
 ---> 5a6bb7613fc8
Successfully built 5a6bb7613fc8
Successfully tagged registry.xxx.com/layer/build:new-1.0.1

推送到仓库可以看到仅推送了application层只有300K

docker push registry.xxx.com/layer/build:new-1.0.1
The push refers to repository [registry.xxx.com/layer/build]
c33a5c6456bd: Pushed
7167dfa406ea: Layer already exists
cf7e94a2dc11: Layer already exists
8e261e1bae2c: Layer already exists
770c31a84800: Layer already exists
c33745b35097: Layer already exists
2105884a1756: Layer already exists
174f56854903: Layer already exists
new-1.0.1: digest: sha256:53647bb45f0f0bb5bb8d56f14cd40deb22f0d5e4fce1200fed1c225a516dddb5 size: 2001

验证镜像

[root@localhost new]# docker run -it --rm -u 1001:1001  -e JAVA_OPTS="-XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCApplicationConcurrentTime -XX:+PrintCommandLineFlags"  registry.xxx.com/layer/build:new-1.0.1

可以看到打印出了堆栈信息（容器默认是不开启的）应用成功启动😋

[root@localhost ~]# docker run -it --rm -u 1001:1001  -e JAVA_OPTS="-XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCApplicationConcurrentTime -XX:+PrintCommandLineFlags"  registry.xxx.com/layer/build:new-1.0.1
-XX:InitialHeapSize=130478208 -XX:MaxHeapSize=2087651328 -XX:+PrintCommandLineFlags -XX:+PrintGCApplicationConcurrentTime -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCDateStamps -XX:+PrintGCDetails -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseParallelGC
{Heap before GC invocations=1 (full 0):
 PSYoungGen      total 37888K, used 32768K [0x00000000d6800000, 0x00000000d9200000, 0x0000000100000000)
  eden space 32768K, 100% used [0x00000000d6800000,0x00000000d8800000,0x00000000d8800000)
  from space 5120K, 0% used [0x00000000d8d00000,0x00000000d8d00000,0x00000000d9200000)
  to   space 5120K, 0% used [0x00000000d8800000,0x00000000d8800000,0x00000000d8d00000)
 ParOldGen       total 86016K, used 0K [0x0000000083800000, 0x0000000088c00000, 0x00000000d6800000)

  eden space 32768K, 0% used [0x00000000d6800000,0x00000000d6800000,0x00000000d8800000)
  from space 5120K, 72% used [0x00000000d8800000,0x00000000d8ba1748,0x00000000d8d00000)
  to   space 5120K, 0% used [0x00000000dad00000,0x00000000dad00000,0x00000000db200000)
 ParOldGen       total 86016K, used 8K [0x0000000083800000, 0x0000000088c00000, 0x00000000d6800000)
  object space 86016K, 0% used [0x0000000083800000,0x0000000083802000,0x0000000088c00000)
 Metaspace       used 6799K, capacity 7074K, committed 7168K, reserved 1056768K
  class space    used 820K, capacity 935K, committed 1024K, reserved 1048576K
}
...
2023-08-17 20:50:42.253  INFO 1 --- [           main] org.springframework.boot.actuate.endpoint.web.EndpointLinksResolver.<init>(EndpointLinksResolver.java:58) - [] : Exposing 1 endpoint(s) beneath base path '/actuator'
2023-08-17 20:50:42.315  INFO 1 --- [           main] org.apache.juli.logging.DirectJDKLog.log(DirectJDKLog.java:173) - [] : Starting ProtocolHandler ["http-nio-8082"]
2023-08-17 20:50:42.349  INFO 1 --- [           main] org.springframework.boot.web.embedded.tomcat.TomcatWebServer.start(TomcatWebServer.java:220) - [] : Tomcat started on port(s): 8082 (http) with context path '/xxx'
2023-08-17 20:50:42.376  INFO 1 --- [           main] org.springframework.boot.StartupInfoLogger.logStarted(StartupInfoLogger.java:61) - [] : Started Application in 11.242 seconds (JVM running for 12.553)

对比两个版本可以发现只有application成hash值不一样代码量增加了253kB-248kB=5KB

[root@localhost new]# docker image history  registry.xxx.com/layer/build:new
IMAGE          CREATED             CREATED BY                                      SIZE      COMMENT
2cce0deab7e2   About an hour ago   /bin/sh -c #(nop)  ENTRYPOINT ["java" "org.s…   0B
555270edceea   About an hour ago   /bin/sh -c #(nop) COPY dir:2f5975d11563ae449…   248kB
75a9584e0952   About an hour ago   /bin/sh -c #(nop) COPY dir:a3bb0870001a0ef25…   18.5kB
1542209ccc8b   About an hour ago   /bin/sh -c #(nop) COPY dir:16d00ea1f180914e2…   252kB
078e3f4a199c   About an hour ago   /bin/sh -c #(nop) COPY dir:1d3190ed598b634a5…   67.1MB
5c19ddda3114   About an hour ago   /bin/sh -c #(nop) WORKDIR /app                  0B
858e77315e6b   About an hour ago   /bin/sh -c mkdir -pv /app/logs && ln -s /app…   9B
63fb6c823893   3 hours ago         /bin/sh -c #(nop)  ENV LC_ALL=en_US.utf8        0B
9304102c278e   3 hours ago         /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai         0B
1869b73a8999   2 years ago         /bin/sh -c set -ex;   cd /tmp;   curl -fsSLO…   302MB
<missing>      2 years ago         /bin/sh -c #(nop)  ENV JAVA_VERSION=8 JAVA_U…   0B
<missing>      2 years ago         /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai LANG…   0B
<missing>      2 years ago         /bin/sh -c set -ex;   yum update -y;   yum i…   116MB
<missing>      2 years ago         /bin/sh -c #(nop)  LABEL maintainer=currycan…   0B
<missing>      2 years ago         /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B
<missing>      2 years ago         /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B
<missing>      2 years ago         /bin/sh -c #(nop) ADD file:b3ebbe8bd304723d4…   204MB
[root@localhost new]# docker image history  registry.xxx.com/layer/build:new-1.0.1
IMAGE          CREATED             CREATED BY                                      SIZE      COMMENT
76aa6233354a   40 minutes ago      /bin/sh -c #(nop)  ENTRYPOINT ["java" "org.s…   0B
0f138b106caf   40 minutes ago      /bin/sh -c #(nop) COPY dir:4d21cc5ce0d92794b…   253kB
75a9584e0952   About an hour ago   /bin/sh -c #(nop) COPY dir:a3bb0870001a0ef25…   18.5kB
1542209ccc8b   About an hour ago   /bin/sh -c #(nop) COPY dir:16d00ea1f180914e2…   252kB
078e3f4a199c   About an hour ago   /bin/sh -c #(nop) COPY dir:1d3190ed598b634a5…   67.1MB
5c19ddda3114   About an hour ago   /bin/sh -c #(nop) WORKDIR /app                  0B
858e77315e6b   About an hour ago   /bin/sh -c mkdir -pv /app/logs && ln -s /app…   9B
63fb6c823893   3 hours ago         /bin/sh -c #(nop)  ENV LC_ALL=en_US.utf8        0B
9304102c278e   3 hours ago         /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai         0B
1869b73a8999   2 years ago         /bin/sh -c set -ex;   cd /tmp;   curl -fsSLO…   302MB
<missing>      2 years ago         /bin/sh -c #(nop)  ENV JAVA_VERSION=8 JAVA_U…   0B
<missing>      2 years ago         /bin/sh -c #(nop)  ENV TZ=Asia/Shanghai LANG…   0B
<missing>      2 years ago         /bin/sh -c set -ex;   yum update -y;   yum i…   116MB
<missing>      2 years ago         /bin/sh -c #(nop)  LABEL maintainer=currycan…   0B
<missing>      2 years ago         /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B
<missing>      2 years ago         /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B
<missing>      2 years ago         /bin/sh -c #(nop) ADD file:b3ebbe8bd304723d4…   204MB

完

上述对开发没有恶意，大家都是辛苦勤劳上进的打工人。哈哈哈又是摸🐟的一天 —Author Logn

引用：spring boot官方文档)

芋道源码 —— 纯源码解析博客

SpringBoot 容器镜像更新只要200k，你敢信？？？

导读

基础环境

基于传统单个jar包构建模式

基础Dockerfile

Base镜像信息

Base镜像大小 622MB

Base镜像history信息

传统构建方式

构建后镜像大小为基础镜像大小 622MB + 2*65M <= 757MB

成品构建history信息

优化Dockerfile

基于spring boot 分层构建方式

探索基于分层构建原理

基于分层构建构建制品镜像

验证模拟开发推送代码更新镜像

验证镜像

导读

基础环境

基于传统单个jar包构建模式

基础Dockerfile

Base镜像信息

Base镜像大小 622MB

Base镜像history信息

传统构建方式

构建后镜像大小 为基础镜像大小 622MB + 2*65M <= 757MB

成品构建history信息

优化Dockerfile

基于spring boot 分层构建方式

探索基于分层构建原理

基于分层构建构建制品镜像

验证模拟开发推送代码更新镜像

验证镜像

构建后镜像大小为基础镜像大小 622MB + 2*65M <= 757MB