Makefile: consolidate docker-build

As part of this commit, I upgraded the golang image used for building to
1.16 and consolidated how the docker-build rule was working. Previously,
it was failing in master's CI because the go modules were not downloaded
in the build image. To improve that, I replaced the combination of
docker run and docker build by a multi-stage Dockerfile responsible for
building the adapter and running it.

In addition to that, I removed the `_output` directory completely as it
wasn't really meaningful to have it anymore. I also removed the
`build-local-image` rule as it was a duplicate of the `docker-build`
rule with the only different of using a scratch base image.

Also, since all the base images that we are using by default are based
on busybox, I change the UID used in the image to 65534 which correspond
to the nobody user in busybox.

Signed-off-by: Damien Grisonnet <dgrisonn@redhat.com>

.gitignore

@@ -1,4 +1,4 @@
 *.swp
 *~
-/_output
 /vendor
+/adapter

Dockerfile

@@ -0,0 +1,22 @@
+ARG BASEIMAGE
+ARG GOIMAGE
+
+FROM ${GOIMAGE} as build
+
+WORKDIR /go/src/sigs.k8s.io/prometheus-adapter
+COPY go.mod .
+COPY go.sum .
+RUN go mod download
+
+COPY pkg pkg
+COPY cmd cmd
+COPY Makefile Makefile
+
+ARG ARCH
+RUN make prometheus-adapter
+
+FROM ${BASEIMAGE}
+
+COPY --from=build /go/src/sigs.k8s.io/prometheus-adapter/adapter /
+USER 65534
+ENTRYPOINT ["/adapter"]

Makefile

@@ -3,12 +3,9 @@ IMAGE?=k8s-prometheus-adapter
 ARCH?=$(shell go env GOARCH)
 ALL_ARCH=amd64 arm arm64 ppc64le s390x
 ML_PLATFORMS=linux/amd64,linux/arm,linux/arm64,linux/ppc64le,linux/s390x
-OUT_DIR?=$(PWD)/_output
 
 VERSION?=latest
-GOIMAGE=golang:1.15
-GO111MODULE=on
-export GO111MODULE
+GOIMAGE=golang:1.16
 
 ifeq ($(ARCH),amd64)
 	BASEIMAGE?=busybox
@@ -26,31 +23,26 @@ ifeq ($(ARCH),s390x)
 	BASEIMAGE?=s390x/busybox
 endif
 
-.PHONY: all docker-build push-% push test verify-gofmt gofmt verify build-local-image
+.PHONY: all
+all: prometheus-adapter
 
-all: $(OUT_DIR)/$(ARCH)/adapter
+# Build
+# -----
 
 src_deps=$(shell find pkg cmd -type f -name "*.go")
-$(OUT_DIR)/%/adapter: $(src_deps)
-	CGO_ENABLED=0 GOARCH=$* go build -tags netgo -o $(OUT_DIR)/$*/adapter sigs.k8s.io/prometheus-adapter/cmd/adapter
+prometheus-adapter: $(src_deps)
+	CGO_ENABLED=0 GOARCH=$(ARCH) go build sigs.k8s.io/prometheus-adapter/cmd/adapter
 
-docker-build: $(OUT_DIR)/Dockerfile
-	docker run -it -v $(OUT_DIR):/build -v $(PWD):/go/src/sigs.k8s.io/prometheus-adapter -e GOARCH=$(ARCH) $(GOIMAGE) /bin/bash -c "\
-		CGO_ENABLED=0 go build -tags netgo -o /build/$(ARCH)/adapter sigs.k8s.io/prometheus-adapter/cmd/adapter"
-
-	docker build -t $(REGISTRY)/$(IMAGE)-$(ARCH):$(VERSION) --build-arg ARCH=$(ARCH) --build-arg BASEIMAGE=$(BASEIMAGE) $(OUT_DIR)
-
-$(OUT_DIR)/Dockerfile: deploy/Dockerfile
-	mkdir -p $(OUT_DIR)
-	cp deploy/Dockerfile $(OUT_DIR)/Dockerfile
-
-build-local-image: $(OUT_DIR)/Dockerfile $(OUT_DIR)/$(ARCH)/adapter
-	docker build -t $(REGISTRY)/$(IMAGE)-$(ARCH):$(VERSION) --build-arg ARCH=$(ARCH) --build-arg BASEIMAGE=scratch $(OUT_DIR)
+.PHONY: docker-build
+docker-build:
+	docker build -t $(REGISTRY)/$(IMAGE)-$(ARCH):$(VERSION) --build-arg ARCH=$(ARCH) --build-arg BASEIMAGE=$(BASEIMAGE) --build-arg GOIMAGE=$(GOIMAGE) .
 
+.PHONY: push-%
 push-%:
 	$(MAKE) ARCH=$* docker-build
 	docker push $(REGISTRY)/$(IMAGE)-$*:$(VERSION)
 
+.PHONY: push
 push: ./manifest-tool $(addprefix push-,$(ALL_ARCH))
 	./manifest-tool push from-args --platforms $(ML_PLATFORMS) --template $(REGISTRY)/$(IMAGE)-ARCH:$(VERSION) --target $(REGISTRY)/$(IMAGE):$(VERSION)
 
@@ -58,15 +50,19 @@ push: ./manifest-tool $(addprefix push-,$(ALL_ARCH))
 	curl -sSL https://github.com/estesp/manifest-tool/releases/download/v0.5.0/manifest-tool-linux-amd64 > manifest-tool
 	chmod +x manifest-tool
 
+.PHONY: test
 test:
 	CGO_ENABLED=0 go test ./cmd/... ./pkg/...
 
+.PHONY: verify-gofmt
 verify-gofmt:
 	./hack/gofmt-all.sh -v
 
+.PHONY: gofmt
 gofmt:
 	./hack/gofmt-all.sh
 
+.PHONY: verify
 verify: verify-gofmt verify-deps verify-generated test
 
 .PHONY: update

deploy/Dockerfile

@@ -1,6 +0,0 @@
-ARG BASEIMAGE
-FROM ${BASEIMAGE}
-ARG ARCH
-COPY ${ARCH}/adapter /
-USER 1001:1001
-ENTRYPOINT ["/adapter"]

docs/walkthrough.md

@@ -46,8 +46,7 @@ an x86_64 machine, use the `directxman12/k8s-prometheus-adapter-amd64`
 image.
 
 If you're feeling adventurous, you can build the latest version of the
-custom metrics adapter by running `make docker-build` or `make
-build-local-image`.
+custom metrics adapter by running `make docker-build`.
 
 Special thanks to [@luxas](https://github.com/luxas) for providing the
 demo application for this walkthrough.