Build cluster autoscaler container images

Add Dockerfile and CI config for building cluster autoscaler
container images specifically for magnum.
The autoscaler is built with the build tag "magnum" so that
only the magnum provider is included in the binary. This cuts
the size of the image in half compared to building with all
cloud providers.
The container-build job in .zuul.yaml has to have its timeout
increased, as the build time was already close to the timeout.

Change-Id: Iecbae5866278afe1687a4533b71af60fce537a4a

.zuul.yaml

@@ -346,7 +346,7 @@
     post-run: playbooks/container-builder-copy-logs.yaml
     roles:
       - zuul: openstack/openstack-zuul-jobs
-    timeout: 1200
+    timeout: 1800
     irrelevant-files:
       - ^.*\.rst$
       - ^api-ref/.*$

dockerfiles/cluster-autoscaler/Dockerfile

@@ -0,0 +1,15 @@
+FROM golang:1.12.10 as builder
+
+ARG AUTOSCALER_VERSION
+
+ENV GOPATH=/go
+
+WORKDIR $GOPATH/src/k8s.io/
+RUN git clone -b ${AUTOSCALER_VERSION} --single-branch http://github.com/kubernetes/autoscaler.git autoscaler
+WORKDIR autoscaler/cluster-autoscaler
+RUN CGO_ENABLED=0 GOOS=linux go build -o cluster-autoscaler --ldflags=-s --tags magnum
+
+FROM gcr.io/distroless/static:latest
+
+COPY --from=builder /go/src/k8s.io/autoscaler/cluster-autoscaler/cluster-autoscaler /cluster-autoscaler
+CMD ["/cluster-autoscaler"]

playbooks/container-builder-vars.yaml

@@ -19,3 +19,7 @@ magnum_images:
     tag: train-dev
 
 helm_version: v2.12.3
+
+cluster_autoscaler_versions:
+  - version: 1.15.2
+  - version: 1.16.1

playbooks/container-builder.yaml

@@ -105,3 +105,16 @@
               HELM_VERSION: "{{ helm_version }}"
             push: no
           retries: 10
+
+    - name: "Build cluster-autoscaler image"
+      block:
+        - name: "Build {{ magnum_repository }}/cluster-autoscaler:v{{ item.version }}"
+          docker_image:
+            path: "{{ magnum_src_dir }}/dockerfiles/cluster-autoscaler"
+            name: "{{ magnum_repository }}/cluster-autoscaler"
+            tag: "v{{ item.version }}"
+            buildargs:
+              AUTOSCALER_VERSION: "cluster-autoscaler-{{ item.version }}"
+            push: no
+          with_items: "{{ cluster_autoscaler_versions }}"
+          retries: 10

playbooks/container-publish.yaml

@@ -30,3 +30,6 @@
           retries: 10
         - command: docker push {{ magnum_repository }}/helm-client:{{ helm_version }}
           retries: 10
+        - command: docker push {{ magnum_repository }}/cluster-autoscaler:v{{ item.version }}
+          with_items: "{{ cluster_autoscaler_versions }}"
+          retries: 10