tests: build Docker images in parallel

tests/image_prep/_container_setup.yml

@@ -61,8 +61,11 @@
       when: distro == "CentOS"
 
     - file:
-        path: /var/cache/apt
+        path: "{{item}}"
         state: absent
+      with_items:
+      - /var/cache/apt
+      - /var/lib/apt
       when: distro == "Debian"
 
     - user:

tests/image_prep/_user_accounts.yml

@@ -34,6 +34,7 @@
     }}"
   tasks:
     - name: Disable non-localhost SSH for Mitogen users
+      when: false
       blockinfile:
         path: /etc/ssh/sshd_config
         block: |

tests/image_prep/build_docker_images.py

@@ -6,6 +6,7 @@ Build the Docker images used for testing.
 
 import commands
 import os
+import tempfile
 import shlex
 import subprocess
 
@@ -19,25 +20,36 @@ def sh(s, *args):
     return shlex.split(s)
 
 
-for base_image, name in [('debian:stretch', 'debian'),
-                         ('centos:6', 'centos6'),
-                         ('centos:7', 'centos7')]:
-    args = sh('docker run --rm -it -d %s /bin/bash', base_image)
+
+label_by_id = {}
+
+for base_image, label in [('debian:stretch', 'debian'),
+                          ('centos:6', 'centos6'),
+                          ('centos:7', 'centos7')]:
+    args = sh('docker run --rm -it -d -h mitogen-%s %s /bin/bash',
+              label, base_image)
     container_id = subprocess.check_output(args).strip()
+    label_by_id[container_id] = label
+
+with tempfile.NamedTemporaryFile() as fp:
+    fp.write('[all]\n')
+    for id_, label in label_by_id.items():
+        fp.write('%s ansible_host=%s\n' % (label, id_))
+    fp.flush()
+
     try:
         subprocess.check_call(
             cwd=BASEDIR,
-            args=sh('''
-                ansible-playbook -i %s, -c docker setup.yml -vvv
-            ''', container_id)
+            args=sh('ansible-playbook -i %s -c docker setup.yml', fp.name),
         )
 
-        subprocess.check_call(sh('''
-            docker commit
-            --change 'EXPOSE 22'
-            --change 'CMD ["/usr/sbin/sshd", "-D"]'
-            %s
-            mitogen/%s-test
-        ''', container_id, name))
+        for container_id, label in label_by_id.items():
+            subprocess.check_call(sh('''
+                docker commit
+                --change 'EXPOSE 22'
+                --change 'CMD ["/usr/sbin/sshd", "-D"]'
+                %s
+                mitogen/%s-test
+            ''', container_id, label))
     finally:
-        subprocess.check_call(sh('docker rm -f %s', container_id))
+        subprocess.check_call(sh('docker rm -f %s', ' '.join(label_by_id)))