I have a Go project with a large vendor/ directory which almost never changes.
I am trying to use the new go 1.10 build cache feature to speed up my builds in Docker engine locally.
Avoiding recompilation of my vendor/ directory would be enough optimization. So I'm trying to do Go equivalent of this common Dockerfile pattern for Python:
FROM python
COPY requirements.txt . # <-- copy your dependency list
RUN pip install -r requirements.txt # <-- install dependencies
COPY ./src ... # <-- your actual code (everything above is cached)
Similarly I tried:
FROM golang:1.10-alpine
COPY ./vendor ./src/myproject/vendor
RUN go build -v myproject/vendor/... # <-- pre-build & cache "vendor/"
COPY . ./src/myproject
However this is giving "cannot find package" error (likely because you cannot build stuff in vendor/ directly normally either).
Has anyone been able to figure this out?
Here's something that works for me:
FROM golang:1.10-alpine
WORKDIR /usr/local/go/src/github.com/myorg/myproject/
COPY vendor vendor
RUN find vendor -maxdepth 2 -mindepth 2 -type d -exec sh -c 'go install -i github.com/myorg/myproject/{}/... || true' \;
COPY main.go .
RUN go build main.go
It makes sure the vendored libraries are installed first. As long as you don't change a library, you're good.
Just use go install -i ./vendor/....
Consider the following Dockerfile:
FROM golang:1.10-alpine
ARG APP
ENV PTH $GOPATH/src/$APP
WORKDIR $PTH
# Pre-compile vendors.
COPY vendor/ $PTH/vendor/
RUN go install -i ./vendor/...
ADD . $PTH/
# Display time taken and the list of the packages being compiled.
RUN time go build -v
You can test it doing something like:
docker build -t test --build-arg APP=$(go list .) .
On the project I am working on, without pre-compile, it takes ~12sec with 90+ package each time, after, it take ~1.2s with only 3 (only the local ones).
If you still have "cannot find package", it means there are missing vendors. Re-run dep ensure should fix it.
An other tip, unrelated to Go is to have your .dockerignore start with *. i.e. ignore everything and then whitelist what you need.