Added support for repairing issues with specific Docker upgrades (#5)

* Added (optional) support for repairing some issues that occur on specific Docker upgrades.
* Added automated tests that can be run in Vagrant, for this and other things.

.gitignore

@@ -0,0 +1,2 @@
+tests/build
+tests/.vagrant

CHANGES.md

@@ -1,2 +1,13 @@
+Version 2.1:
+ - Change default Docker version to 1.11.2, was 1.5.0
+ - Attempt to handle data volume loss when we update from pre-1.10 to post-1.10.
+   See: https://github.com/docker/docker/issues/20079
+ - Attempt to handle missing volume symlinks when we upgrade pre-1.9 data volumes
+   to a post-1.9.x version.
+ - Add "docker_attempt_upgrade_fixes" configuration variable. This defaults to False;
+   the upgrade fixes mentioned above won't be attempted unless it is set to True.
+ - Added automated tests in the "tests" directory - if you have Vagrant installed, they
+   can be run by "cd tests ; ./run_tests.sh".
+
 Version 2.0:
   - Port to github

README.md

@@ -10,32 +10,47 @@ to manage which version of Docker we install. Because of interdepencies between
 version and software that we install (especially `docker-py`), we have to be careful about
 Docker versions.
 
- -  Our initial deploys used a fixed version of LXC Docker, pinned at `1.5.0`
- -  Our newer deploy will still use a pinned version Docker Engine, but will be able to specify
+  - Our initial deploys used a fixed version of LXC Docker, pinned at `1.5.0`
+  - Our newer deploy will still use a pinned version Docker Engine, but will be able to specify
     their own versions (e.g. `1.8.1`)
 
+Upgrade Support
+---------------
 
-Role Variables
---------------
+Some Docker Engine upgrade paths have known issues. There's code in this role that attempts to
+resolve those issues, with minimum disruption, if those upgrade paths are encountered. The
+intention is to not require containers to be recreated.
 
-The `docker_version` variable controls what version of Docker is installed.
+This code isn't intended to catch everything; an attempt has been made to make it reasonable and
+non-harmful, but it hasn't been tested for all possible upgrade paths, nor with features like
+non-local storage drivers. With that in mind, this behavior is optional and is disabled by default.
 
- -  The default `docker_version` is `1.5.0` (for historical reasons). If select, LXC Docker will be used.
- -  Otherwise, the stated version of Docker Engine will be used (if available).
+The issues we attempt to resolve are documented in the "repair_docker_data_volumes" module.
 
 
-Testing
--------
+Role Variables
+--------------
 
-There are known incompatibilities between some Docker versions and some versions of `docker-py`,
-especially between LXC Docker `1.5.0` and `docker-py>1.1.0`. Using this combination will
-result in Python errors along the lines of:
+  - `docker_version` : this variable controls the version of Docker that is installed. Required.
+    If version `1.5.0` is selected, LXC Docker will be used; otherwise the stated version of
+    Docker Engine will be installed (if available).
+  - `docker_attempt_upgrade_fixes` : False by default. If True, the fixes described in "Upgrade
+    Support" will be attempted
+  - `cgroup_lite_pkg_state` : When installing on an Ubuntu 13.10 host, the role will install the
+    `cgroup-lite` package to provide the required cgroups support. This variable can be set to
+    `latest` - the default - or to `present`. In the former case, the package will be updated, if
+    necessary, when the role is run. In the latter, the package will only be added if it is not
+    present.
+  - `kernel_pkg_state` : For 13.04+, this role will install a `linux-image-extra-<version>`
+    package. This parameter works the same way as `cgroup_lite_package_state`, except controlling
+    this package.
 
-    client and server don't have same version (client : 1.19, server: 1.17)
 
-Fortunately, newer versions of Docker Engine with both newer and older versions of `docker-py`
-appear to be compatible. A `testing.yml` playbook is provided for reference.
+Testing
+-------
 
+There's a directory "tests" with some Ansible playbooks that can be used for verifying role
+behavior. See tests/TESTS.md for more information.
 
 License
 -------

defaults/main.yml

@@ -1,5 +1,9 @@
 ---
-docker_version: 1.5.0
+
 kernel_pkg_state: latest
 cgroup_lite_pkg_state: latest
 ssh_port: 22
+
+docker_role_apt_cache_valid_time: 7200
+
+docker_attempt_upgrade_fixes: False

handlers/main.yml

@@ -1,2 +1,2 @@
 ---
-# handlers file for docker.ubuntu
+

library/collect_container_configs

@@ -0,0 +1,67 @@
+#!/usr/bin/env python2.7
+
+import json
+import os
+import os.path
+
+DOCUMENTATION = '''
+---
+module: collect_container_configs
+short_description: collects container configuration data
+description:
+  - when run, this module collects the contents of container configuration files for
+    all current containers
+  - this can be run before an upgrade to store information that would be used after
+    an upgrade
+  - this is returned as a single string containing parsable JSON.
+'''
+
+
+CONTAINER_ROOT_DIR = '/var/lib/docker/containers'
+
+
+CONFIG_FILENAME_OPTIONS = [
+    ('config.v3.json', 3),
+    ('config.v2.json', 2),
+    ('config.json', 1)
+]
+
+
+def main():
+    module = AnsibleModule(
+        argument_spec=dict(),
+        supports_check_mode=True)
+
+    configs = {}
+    config_versions = {}
+
+    if os.path.isdir(CONTAINER_ROOT_DIR):
+        for container in os.listdir(CONTAINER_ROOT_DIR):
+            container_path = os.path.join(CONTAINER_ROOT_DIR, container)
+            if not os.path.isdir(container_path):
+                # we only expect directories here. Ignore the unexpected
+                continue
+
+            for basename, version in CONFIG_FILENAME_OPTIONS:
+                config_path = os.path.join(container_path, basename)
+                if os.path.isfile(config_path):
+                    break
+            else:
+                # no config file was found
+                continue
+
+            with file(config_path, 'r') as f:
+                config = json.load(f)
+
+            configs[container] = config
+            config_versions[container] = version
+
+    module.exit_json(
+            changed=False,
+            configs=configs,
+            config_versions=config_versions)
+
+
+from ansible.module_utils.basic import *
+if __name__ == '__main__':
+    main()