在CircleCI中缓存Docker镜像

Question

我正在使用CircleCI运行测试和部署Docker镜像，但我在缓存Docker镜像时遇到了问题，导致构建时间非常长。

下面是一个不起作用的最小示例：

circle.yml

machine:
   services:
      - docker

dependencies:
    cache_directories:
      - "~/docker"
    override:
      - if [[ -e ~/docker/image.tar ]]; then echo "cached files exists!" ; docker load -i ~/docker/image.tar; fi
      - docker images
      - docker build -t myorg/myapp:v1.1.1 .
      - mkdir -p ~/docker; docker save myorg/myapp:v1.1.1 > ~/docker/image.tar

Dockerfile：

FROM debian:latest
MAINTAINER My Name <myname@gmail.com>
RUN apt-get update && apt-get install -y vim
CMD ["sleep", "3"]

在推送到GitHub时，构建在CircleCI中运行得很好。但Docker镜像在每次运行时都会重新构建。这在生产Docker映像中变得非常耗时。

文件image.tar被清楚地加载了，这从docker images命令的输出中看得很清楚，但是即使does文件没有改变，每次它仍然构建总的镜像。

下面是docker build -t myorg/myapp:v1.1.1 .行的一些输出

docker build -t myorg/myapp:v1.1.1 .
Sending build context to Docker daemon 67.07 kB


Step 1 : FROM debian:latest
latest: Pulling from library/debian


Digest: sha256:370807fef6f790d8519399026d26461bdf8360f94ab450da94c2350bea3cc66d
Status: Downloaded newer image for debian:latest
 ---> ae85c48b369c
Step 2 : MAINTAINER My Name <myname@gmail.com>
 ---> Running in 4ffd69c2a82d
 ---> 6029750ba0f3
Error removing intermediate container 4ffd69c2a82d: rmdriverfs: Driver btrfs failed to remove root filesystem 4ffd69c2a82d644ea7ee8576cc06e67ee412f651edecbc40932394c057aa931d: Failed to destroy btrfs snapshot /var/lib/docker/btrfs/subvolumes for 4ffd69c2a82d644ea7ee8576cc06e67ee412f651edecbc40932394c057aa931d: operation not permitted
Step 3 : RUN apt-get update && apt-get install -y vim
 ---> Running in 544047b8c170
Ign http://httpredir.debian.org jessie InRelease
Get:1 http://httpredir.debian.org jessie-updates InRelease [142 kB]
Get:2 http://httpredir.debian.org jessie Release.gpg [2373 B]
Get:3 http://httpredir.debian.org jessie Release [148 kB]
Get:4 http://security.debian.org jessie/updates InRelease [63.1 kB]
Get:5 http://httpredir.debian.org jessie-updates/main amd64 Packages [17.6 kB]
Get:6 http://httpredir.debian.org jessie/main amd64 Packages [9064 kB]
Get:7 http://security.debian.org jessie/updates/main amd64 Packages [390 kB]
Fetched 9828 kB in 2s (4030 kB/s)
Reading package lists...
Reading package lists...
Building dependency tree...
The following extra packages will be installed:
  libgpm2 vim-common vim-runtime
Suggested packages:
  gpm ctags vim-doc vim-scripts
The following NEW packages will be installed:
  libgpm2 vim vim-common vim-runtime
0 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.
Need to get 6218 kB of archives.
After this operation, 28.9 MB of additional disk space will be used.
Get:1 http://httpredir.debian.org/debian/ jessie/main libgpm2 amd64 1.20.4-6.1+b2 [34.0 kB]
Get:2 http://httpredir.debian.org/debian/ jessie/main vim-common amd64 2:7.4.488-7 [184 kB]
Get:3 http://httpredir.debian.org/debian/ jessie/main vim-runtime all 2:7.4.488-7 [5047 kB]
Get:4 http://httpredir.debian.org/debian/ jessie/main vim amd64 2:7.4.488-7 [953 kB]
debconf: delaying package configuration, since apt-utils is not installed
Fetched 6218 kB in 0s (10.7 MB/s)
Selecting previously unselected package libgpm2:amd64.

你知道为什么它每次都要重建docker镜像吗？

Answer 1

现在，您可以在CircleCI上启用docker层缓存。这是一个高级功能。它将重用以前用于构建图像的层。

https://circleci.com/docs/2.0/docker-layer-caching/