Now let's imagine that we want to add some dependencies to our app. In Go, that means adding go.mod and go.sum.
./go.mod
module github.com/earthly/earthly/examples/go
go 1.13
require github.com/sirupsen/logrus v1.5.0
./go.sum (empty)
The code of the app might look like this
./main.go
package main
import "github.com/sirupsen/logrus"
func main() {
logrus.Info("hello world")
}
Now we can update our Earthfile to copy in the go.mod and go.sum.
./Earthfile
VERSION 0.6
FROM golang:1.15-alpine3.13
WORKDIR /go-workdir
build:
COPY go.mod go.sum .
COPY main.go .
RUN go build -o output/example main.go
SAVE ARTIFACT output/example AS LOCAL local-output/go-example
docker:
COPY +build/example .
ENTRYPOINT ["/go-workdir/example"]
SAVE IMAGE go-example:latest
This works, but it is inefficient because we have not made proper use of caching. In the current setup, when a file changes, the corresponding COPY command is re-executed without cache, causing all commands after it to also re-execute without cache.
Caching
If, however, we could first download the dependencies and only afterwards copy and build the code, then the cache would be reused every time we changed the code.
./Earthfile
VERSION 0.6
FROM golang:1.15-alpine3.13
WORKDIR /go-workdir
build:
# Download deps before copying code.
COPY go.mod go.sum .
RUN go mod download
# Copy and build code.
COPY main.go .
RUN go build -o output/example main.go
SAVE ARTIFACT output/example AS LOCAL local-output/go-example
docker:
COPY +build/example .
ENTRYPOINT ["/go-workdir/example"]
SAVE IMAGE go-example:latest
Reusing Dependencies
In some cases, the dependencies might be used in more than one build target. For this use case, we might want to separate dependency downloading and reuse it. For this reason, let's consider breaking this out into a separate target called +deps. We can then inherit from +deps by using the command FROM +deps.
./Earthfile
VERSION 0.6
FROM golang:1.15-alpine3.13
WORKDIR /go-workdir
deps:
COPY go.mod go.sum ./
RUN go mod download
# Output these back in case go mod download changes them.
SAVE ARTIFACT go.mod AS LOCAL go.mod
SAVE ARTIFACT go.sum AS LOCAL go.sum
build:
FROM +deps
COPY main.go .
RUN go build -o output/example main.go
SAVE ARTIFACT output/example AS LOCAL local-output/go-example
docker:
COPY +build/example .
ENTRYPOINT ["/go-workdir/example"]
SAVE IMAGE go-example:latest
Note that in our case, only the JavaScript version has an example where FROM +deps is used in more than one place: both in build and in docker. Nevertheless, all versions show how dependencies may be separated.
./Earthfile
VERSION 0.6
FROM node:13.10.1-alpine3.11
WORKDIR /js-example
deps:
COPY package.json ./
COPY package-lock.json ./
RUN npm install
# Output these back in case npm install changes them.
SAVE ARTIFACT package.json AS LOCAL ./package.json
SAVE ARTIFACT package-lock.json AS LOCAL ./package-lock.json
build:
FROM +deps
COPY src src
RUN mkdir -p ./dist && cp ./src/index.html ./dist/
RUN npx webpack
SAVE ARTIFACT dist /dist AS LOCAL dist
docker:
FROM +deps
COPY +build/dist ./dist
EXPOSE 8080
ENTRYPOINT ["/js-example/node_modules/http-server/bin/http-server", "./dist"]
SAVE IMAGE js-example:latest
VERSION 0.6
FROM openjdk:8-jdk-alpine
RUN apk add --update --no-cache gradle
WORKDIR /java-example
deps:
COPY build.gradle ./
RUN gradle build
build:
FROM +deps
COPY src src
RUN gradle build
RUN gradle install
SAVE ARTIFACT build/install/java-example/bin AS LOCAL build/bin
SAVE ARTIFACT build/install/java-example/lib AS LOCAL build/lib
docker:
COPY +build/bin bin
COPY +build/lib lib
ENTRYPOINT ["/java-example/bin/java-example"]
SAVE IMAGE java-example:latest
