install-docker: enable setting docker userland proxy

This change enables docker user to disable the userland proxy.

Do not merge until the default is set to false (used for testing).

Change-Id: Ib30e409044ccc48b4c19beae36f1bcd453ebef8e

roles/install-docker/README.rst

@@ -75,3 +75,10 @@ An ansible role to install docker and configure it to use mirrors if available.
    based on :zuul:rolevar:`install-docker.docker_download_fqdn`. When this
    option is unset, the role will use distro specific variables which are
    loaded at the time of execution.
+
+.. zuul:rolevar:: docker_userland_proxy
+   :type: bool
+
+   Set to false to disable the docker userland proxy. This variable is useful
+   when docker is causing routing problem, such as when a kubernetes deployment
+   is unable to reach its own service.

roles/install-docker/tasks/docker-setup.yaml

@@ -12,5 +12,37 @@
       - "{{ docker_group }}"
     append: yes
 
+- name: Update docker daemon configuration
+  when: docker_userland_proxy is defined
+  block:
+    - name: Check if docker daemon configuration exists
+      stat:
+        path: /etc/docker/daemon.json
+      register: docker_config_stat
+    - name: Load docker daemon configuration
+      when: docker_config_stat.stat.exists
+      slurp:
+        path: /etc/docker/daemon.json
+      register: docker_config
+    - name: Parse docker daemon configuration
+      when: docker_config_stat.stat.exists
+      set_fact:
+        docker_config: "{{ docker_config.content | b64decode | from_json }}"
+    - name: Set default docker daemon configuration
+      when: not docker_config_stat.stat.exists
+      set_fact:
+        docker_config: {}
+    - name: Add registry to docker daemon configuration
+      vars:
+        new_config:
+          userland-proxy: "{{ docker_userland_proxy }}"
+      set_fact:
+        docker_config: "{{ docker_config | combine(new_config) }}"
+    - name: Save docker daemon configuration
+      copy:
+        content: "{{ docker_config | to_nice_json }}"
+        dest: /etc/docker/daemon.json
+      become: true
+
 - name: Reset ssh connection to pick up docker group
-  meta: reset_connection
+  meta: reset_connection