Enable building multi-arch docker images for s390x

.dockerignore

@@ -1,4 +1,3 @@
-.*
 vendor
 Dockerfile
 Makefile

.travis.yml

@@ -1,16 +1,25 @@
 sudo: required
 
-services:
-- docker
-
 language: go
 
 go:
 - 1.16
 
+env:
+- GOFLAGS="-mod=readonly"
+
+before_install:
+  - sudo rm -rf /var/lib/apt/lists/*
+  - curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
+  - sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) edge"
+  - sudo apt-get update
+  - sudo apt-get -y -o Dpkg::Options::="--force-confnew" install docker-ce
+  - mkdir -vp ~/.docker/cli-plugins/
+  - curl --silent -L "https://github.com/docker/buildx/releases/download/v0.6.1/buildx-v0.6.1.linux-amd64" > ~/.docker/cli-plugins/docker-buildx
+  - chmod a+x ~/.docker/cli-plugins/docker-buildx
+
 after_success:
 - if [ "$TRAVIS_PULL_REQUEST" == "false" ]; then
-  make docker;
   make push;
   fi
 - if [[ -n "$TRAVIS_TAG" ]]; then

Dockerfile

@@ -1,7 +1,10 @@
 FROM        quay.io/prometheus/busybox:latest
 MAINTAINER  Daniel Qian <[email protected]>
 
-COPY kafka_exporter /bin/kafka_exporter
+ARG TARGETARCH
+ARG BIN_DIR=.build/linux-${TARGETARCH}/
+
+COPY ${BIN_DIR}/kafka_exporter /bin/kafka_exporter
 
 EXPOSE     9308
-ENTRYPOINT [ "/bin/kafka_exporter" ]
+ENTRYPOINT [ "/bin/kafka_exporter" ]

Makefile

@@ -8,6 +8,9 @@ DOCKER_IMAGE_NAME       ?= kafka-exporter
 DOCKER_IMAGE_TAG        ?= $(subst /,-,$(shell git rev-parse --abbrev-ref HEAD))
 TAG 					:= $(shell echo `if [ "$(TRAVIS_BRANCH)" = "master" ] || [ "$(TRAVIS_BRANCH)" = "" ] ; then echo "latest"; else echo $(TRAVIS_BRANCH) ; fi`)
 
+PUSHTAG                 ?= type=registry,push=true
+DOCKER_PLATFORMS        ?= linux/amd64,linux/s390x
+
 all: format build test
 
 style:
@@ -29,6 +32,7 @@ vet:
 build: promu
 	@echo ">> building binaries"
 	@$(PROMU) build --prefix $(PREFIX)
+	@$(GO) mod vendor
 
 crossbuild: promu
 	@echo ">> crossbuilding binaries"
@@ -40,13 +44,16 @@ tarball: promu
 
 docker: build
 	@echo ">> building docker image"
-	@docker build -t "$(DOCKER_IMAGE_NAME):$(DOCKER_IMAGE_TAG)" .
+	@docker build -t "$(DOCKER_IMAGE_NAME):$(DOCKER_IMAGE_TAG)" --build-arg BIN_DIR=. .
 
-push:
-	@echo ">> pushing docker image, $(DOCKER_USERNAME),$(DOCKER_IMAGE_NAME),$(TAG)"
+push: crossbuild
+	@echo ">> building and pushing multi-arch docker images, $(DOCKER_USERNAME),$(DOCKER_IMAGE_NAME),$(TAG)"
 	@docker login -u $(DOCKER_USERNAME) -p $(DOCKER_PASSWORD)
-	@docker tag "$(DOCKER_IMAGE_NAME):$(DOCKER_IMAGE_TAG)" "$(DOCKER_USERNAME)/$(DOCKER_IMAGE_NAME):$(TAG)"
-	@docker push "$(DOCKER_USERNAME)/$(DOCKER_IMAGE_NAME):$(TAG)"
+	@docker buildx create --use
+	@docker buildx build -t "$(DOCKER_USERNAME)/$(DOCKER_IMAGE_NAME):$(TAG)" \
+		--output "$(PUSHTAG)" \
+		--platform "$(DOCKER_PLATFORMS)" \
+		.
 
 release: promu github-release
 	@echo ">> pushing binary to github with ghr"