Pull and prune docker images together

We noticed that our zuul scheduler was running out of disk and one of
the causes of this is we are pulling all of the wonderful new zuul
images and not pruning them. This happens because we were only pruning
when (re)starting services and we don't do that automatically with Zuul.
Address this by always pruning after pulling even if we don't restart
services. This should be safe because prune will leave the latest tagged
images as well as the running images.

This should keep our disk consumption down.

Change-Id: Ibdd22ac42d86781f1e87c3d11e05fd8f99677167

playbooks/roles/nodepool-builder/tasks/main.yaml

@@ -41,6 +41,10 @@
     cmd: docker-compose up -d
     chdir: /etc/nodepool-builder-compose/
 
+- name: Run docker prune to cleanup unneeded images
+  shell:
+    cmd: docker image prune -f
+
 - name: Disable old service
   service:
     name: nodepool-builder

playbooks/roles/nodepool-launcher/tasks/main.yaml

@@ -54,6 +54,12 @@
   include_tasks: start.yaml
   when: nodepool_launcher_start | bool
 
+# We can prune here as it should leave the "latest" tagged images
+# as well as the currently running images.
+- name: Run docker prune to cleanup unneeded images
+  shell:
+    cmd: docker image prune -f
+
 - name: Disable old service
   service:
     name: nodepool-launcher

playbooks/roles/nodepool-launcher/tasks/start.yaml

@@ -2,7 +2,3 @@
   shell:
     cmd: docker-compose up -d
     chdir: /etc/nodepool-docker/
-
-- name: Run docker prune to cleanup unneeded images
-  shell:
-    cmd: docker image prune -f

playbooks/roles/zuul-merger/tasks/main.yaml

@@ -51,6 +51,12 @@
   include_tasks: start.yaml
   when: zuul_merger_start | bool
 
+# We can prune here as it should leave the "latest" tagged images
+# as well as the currently running images.
+- name: Run docker prune to cleanup unneeded images
+  shell:
+    cmd: docker image prune -f
+
 - name: Disable old service
   service:
     name: zuul-merger

playbooks/roles/zuul-merger/tasks/start.yaml

@@ -2,7 +2,3 @@
   shell:
     cmd: docker-compose up -d
     chdir: /etc/zuul-merger
-
-- name: Run docker prune to cleanup unneeded images
-  shell:
-    cmd: docker image prune -f

playbooks/roles/zuul-scheduler/tasks/main.yaml

@@ -72,6 +72,12 @@
   include_tasks: start.yaml
   when: zuul_scheduler_start is defined and zuul_scheduler_start | bool
 
+# We can prune here as it should leave the "latest" tagged images
+# as well as the currently running images.
+- name: Run docker prune to cleanup unneeded images
+  shell:
+    cmd: docker image prune -f
+
 - name: Disable old service
   service:
     name: zuul-scheduler

playbooks/roles/zuul-scheduler/tasks/start.yaml

@@ -2,8 +2,3 @@
   shell:
     cmd: docker-compose up -d
     chdir: /etc/zuul-scheduler
-
-# TODO: put this in a handler
-- name: Run docker prune to cleanup unneeded images
-  shell:
-    cmd: docker image prune -f

playbooks/roles/zuul-web/tasks/main.yaml

@@ -100,6 +100,12 @@
   include_tasks: start.yaml
   when: zuul_web_start | bool
 
+# We can prune here as it should leave the "latest" tagged images
+# as well as the currently running images.
+- name: Run docker prune to cleanup unneeded images
+  shell:
+    cmd: docker image prune -f
+
 - name: Disable old service
   service:
     name: 'zuul-{{ item }}'

playbooks/roles/zuul-web/tasks/start.yaml

@@ -2,7 +2,3 @@
   shell:
     cmd: docker-compose up -d
     chdir: /etc/zuul-web
-
-- name: Run docker prune to cleanup unneeded images
-  shell:
-    cmd: docker image prune -f