Build lightstep image based on alpine

Signed-off-by: Mikkel Oscar Lyderik Larsen <mikkel.larsen@zalando.de>

packaging/Dockerfile.lightstep

@@ -1,7 +1,24 @@
-FROM registry.opensource.zalan.do/stups/ubuntu:latest
+# builder image
+FROM golang:alpine as builder
+
+RUN apk add -U git && \
+    go get github.com/Masterminds/glide
+COPY . .
+RUN go get -d github.com/skipper-plugins/opentracing && \
+    cd /go/src/github.com/skipper-plugins/opentracing && \
+    glide install --strip-vendor && \
+    GOOS=linux GOARCH=amd64 CGO_ENABLED=1 make
+
+# final image
+FROM alpine
 MAINTAINER Skipper Maintainers <team-pathfinder@zalando.de>
+RUN apk --no-cache add ca-certificates && update-ca-certificates
+RUN mkdir -p /usr/bin
 ADD skipper eskip /usr/bin/
-EXPOSE 9090 9911
+ENV PATH $PATH:/usr/bin
 RUN mkdir -p /plugins
-ADD build/tracing_lightstep.so /plugins/
+COPY --from=builder /go/src/github.com/skipper-plugins/opentracing/build/tracing_lightstep.so /plugins/
+
+EXPOSE 9090 9911
+
 ENTRYPOINT ["/usr/bin/skipper", "-plugindir", "/plugins"]

packaging/Makefile

@@ -31,7 +31,7 @@ plugins:
 		GOOS=linux GOARCH=amd64 CGO_ENABLED=1 make ;\
 		cp build/*.so $$CUR/build/
 
-docker-lightstep-build: skipper eskip plugins
+docker-lightstep-build: skipper eskip
 	docker build -t $(LIGHTSTEP_IMAGE) -f Dockerfile.lightstep .
 
 docker-lightstep-push: