问题
I am trying to implement Buildkit's cache mount feature.
My Dockerfile is:
# syntax = docker/dockerfile:experimental
FROM python:3.6-alpine
RUN --mount=type=cache,target=/root/.cache/pip pip install pyyaml
CMD: docker build --progress=plain -t abc:1 . --no-cache
First Run Output:
#2 [internal] load .dockerignore
#2 transferring context: 2B done
#2 DONE 0.0s
#1 [internal] load build definition from Dockerfile
#1 transferring dockerfile: 175B done
#1 DONE 0.0s
#3 resolve image config for docker.io/docker/dockerfile:experimental
#3 DONE 2.8s
#4 docker-image://docker.io/docker/dockerfile:experimental@sha256:787107d7f...
#4 CACHED
#5 [internal] load metadata for docker.io/library/python:3.6-alpine
#5 DONE 0.0s
#6 [stage-0 1/2] FROM docker.io/library/python:3.6-alpine
#6 CACHED
#7 [stage-0 2/2] RUN --mount=type=cache,target=/root/.cache/pip pip install...
#7 1.410 Collecting pyyaml
#7 1.731 Downloading PyYAML-5.3.1.tar.gz (269 kB)
#7 2.470 Building wheels for collected packages: pyyaml
#7 2.471 Building wheel for pyyaml (setup.py): started
#7 2.801 Building wheel for pyyaml (setup.py): finished with status 'done'
#7 2.802 Created wheel for pyyaml: filename=PyYAML-5.3.1-cp36-cp36m-linux_x86_64.whl size=44621 sha256=0bfa8470e677b8c2e1d50f8749aa5890b5fb7d7d15352596fbd928c846f9922d
#7 2.802 Stored in directory: /root/.cache/pip/wheels/e5/9d/ad/2ee53cf262cba1ffd8afe1487eef788ea3f260b7e6232a80fc
#7 2.803 Successfully built pyyaml
#7 2.835 Installing collected packages: pyyaml
#7 2.882 Successfully installed pyyaml-5.3.1
#7 DONE 3.3s
#8 exporting to image
#8 exporting layers
#8 exporting layers 0.1s done
#8 writing image sha256:d7ecd86c64611e14f55fa2d31b8f440246e356026eef7175526ccc921373c205 done
#8 naming to docker.io/library/abc:1 done
#8 DONE 0.1s
Second Run Output:
#1 [internal] load .dockerignore
#1 transferring context: 2B done
#1 DONE 0.0s
#2 [internal] load build definition from Dockerfile
#2 transferring dockerfile: 37B done
#2 DONE 0.0s
#3 resolve image config for docker.io/docker/dockerfile:experimental
#3 DONE 2.7s
#4 docker-image://docker.io/docker/dockerfile:experimental@sha256:787107d7f...
#4 CACHED
#5 [internal] load metadata for docker.io/library/python:3.6-alpine
#5 DONE 0.0s
#6 [stage-0 1/2] FROM docker.io/library/python:3.6-alpine
#6 CACHED
#7 [stage-0 2/2] RUN --mount=type=cache,target=/root/.cache/pip pip install...
#7 1.385 Collecting pyyaml
#7 1.773 Downloading PyYAML-5.3.1.tar.gz (269 kB)
#7 2.517 Building wheels for collected packages: pyyaml
#7 2.518 Building wheel for pyyaml (setup.py): started
#7 2.844 Building wheel for pyyaml (setup.py): finished with status 'done'
#7 2.846 Created wheel for pyyaml: filename=PyYAML-5.3.1-cp36-cp36m-linux_x86_64.whl size=44621 sha256=064a160d2f195ad7753fba5abf9481b40b515fadffc94f30aef20146209a0faa
#7 2.846 Stored in directory: /root/.cache/pip/wheels/e5/9d/ad/2ee53cf262cba1ffd8afe1487eef788ea3f260b7e6232a80fc
#7 2.846 Successfully built pyyaml
#7 2.877 Installing collected packages: pyyaml
#7 2.920 Successfully installed pyyaml-5.3.1
#7 DONE 3.3s
#8 exporting to image
#8 exporting layers
#8 exporting layers 0.1s done
#8 writing image sha256:42525b426b00a8728b735c15efb96bd237fc020f46d6d99f5bfebb7758016e71 done
#8 naming to docker.io/library/abc:1 done
#8 DONE 0.1s
Expected:
In the second run, I was expecting pyyaml to be picked from the cache.
OS: Mac OS Catalina (10.15.3)
Docker Version:
Ref: https://stackoverflow.com/a/58021389/1060337
回答1:
You could add mode=0777 for example to Dockerfile to make it work.
Dockerfile:
# syntax = docker/dockerfile:experimental
FROM python:3.6-alpine
RUN --mount=type=cache,mode=0777,target=/root/.cache/pip pip install pyyaml
Here,
mode: File mode for new cache directory in octal. Default 0755.
The 1st run:
#8 [stage-0 2/2] RUN --mount=type=cache,mode=0777,target=/root/.cache/pip p...
#8 2.085 Collecting pyyaml
#8 2.455 Downloading PyYAML-5.3.1.tar.gz (269 kB)
#8 3.484 Building wheels for collected packages: pyyaml
#8 3.485 Building wheel for pyyaml (setup.py): started
#8 3.864 Building wheel for pyyaml (setup.py): finished with status 'done'
#8 3.865 Created wheel for pyyaml: filename=PyYAML-5.3.1-cp36-cp36m-linux_x86_64.whl size=44621 sha256=372ab164f3e88d66fa2571fa048317b22a7c48bf723dfecbac4e058e9037c4fd
#8 3.865 Stored in directory: /root/.cache/pip/wheels/e5/9d/ad/2ee53cf262cba1ffd8afe1487eef788ea3f260b7e6232a80fc
#8 3.866 Successfully built pyyaml
#8 3.901 Installing collected packages: pyyaml
#8 3.961 Successfully installed pyyaml-5.3.1
#8 DONE 4.7s
The 2nd run:
#8 [stage-0 2/2] RUN --mount=type=cache,mode=0777,target=/root/.cache/pip p...
#8 2.069 Processing /root/.cache/pip/wheels/e5/9d/ad/2ee53cf262cba1ffd8afe1487eef788ea3f260b7e6232a80fc/PyYAML-5.3.1-cp36-cp36m-linux_x86_64.whl
#8 2.112 Installing collected packages: pyyaml
#8 2.166 Successfully installed pyyaml-5.3.1
#8 DONE 2.5s
UPDATE:
If I use next for experiment:
RUN --mount=type=cache,target=/root/.cache/pip ls -alh /root/.cache/pip;pip install pyyaml;ls -alh /root/.cache/pip
I could see next:
#7 [stage-0 2/2] RUN --mount=type=cache,target=/root/.cache/pip ls -alh /ro...
#7 0.405 total 8K
#7 0.405 drwxr-xr-x 2 root root 4.0K Apr 29 01:04 .
#7 0.405 drwxr-xr-x 3 root root 4.0K Apr 29 01:04 ..
#7 1.957 Collecting pyyaml
#7 2.572 Downloading PyYAML-5.3.1.tar.gz (269 kB)
#7 3.552 Building wheels for collected packages: pyyaml
#7 3.553 Building wheel for pyyaml (setup.py): started
#7 3.885 Building wheel for pyyaml (setup.py): finished with status 'done'
#7 3.887 Created wheel for pyyaml: filename=PyYAML-5.3.1-cp36-cp36m-linux_x86_64.whl size=44621 sha256=4c971f0f901ff8ed3a20c5bb7d94069f15249c665ebe611430db17cb87969cc7
#7 3.887 Stored in directory: /root/.cache/pip/wheels/e5/9d/ad/2ee53cf262cba1ffd8afe1487eef788ea3f260b7e6232a80fc
#7 3.888 Successfully built pyyaml
#7 3.918 Installing collected packages: pyyaml
#7 3.972 Successfully installed pyyaml-5.3.1
#7 4.451 WARNING: You are using pip version 20.0.2; however, version 20.1 is available.
#7 4.451 You should consider upgrading via the '/usr/local/bin/python -m pip install --upgrade pip' command.
#7 4.512 total 20K
#7 4.512 drwxr-xr-x 5 root root 4.0K Apr 29 01:04 .
#7 4.512 drwxr-xr-x 3 root root 4.0K Apr 29 01:04 ..
#7 4.512 drwxr-xr-x 5 root root 4.0K Apr 29 01:04 http
#7 4.512 drwxr-xr-x 2 root root 4.0K Apr 29 01:04 selfcheck
#7 4.512 drwxr-xr-x 3 root root 4.0K Apr 29 01:04 wheels
#7 DONE 4.7s
Rerun above again, the things same. So looks like if not set mode, the buildkit won't mount a cache from docker host. But if set a mode mode, even with 0755, it's ok.
So, now I strongly guess it's a bug of buildkit on MACOS, that is: if not set mode, it will not mount cache for you. But the behavior is ok on linux.
来源：https://stackoverflow.com/questions/61459775/docker-buildkit-mount-type-cache-not-working-why