Replace multi-role checks with action plugin

This approach should make it easier to add new checks without having to
write lots of YAML and doing things against Ansible (e.g.
ignore_errors).

A single action plugin determines what checks to run per each host,
including arguments to the check. A check is implemented as a class with
a run method, with the same signature as an action plugin and module,
and is normally backed by a regular Ansible module.

Each check is implemented as a separate Python file. This allows whoever
adds a new check to focus solely in a single Python module, and
potentially an Ansible module within library/ too.

All checks are automatically loaded, and only active checks that are
requested by the playbook get executed.

1 files changed, 100 insertions, 0 deletions

diff --git a/roles/openshift_health_checker/callback_plugins/zz_failure_summary.py b/roles/openshift_health_checker/callback_plugins/zz_failure_summary.py
new file mode 100644
index 000000000..8caefab15
--- /dev/null
+++ b/roles/openshift_health_checker/callback_plugins/zz_failure_summary.py
@@ -0,0 +1,100 @@
+# vim: expandtab:tabstop=4:shiftwidth=4
+'''
+Ansible callback plugin.
+'''
+
+from pprint import pformat
+
+from ansible.plugins.callback import CallbackBase
+from ansible import constants as C
+from ansible.utils.color import stringc
+
+
+class CallbackModule(CallbackBase):
+    '''
+    This callback plugin stores task results and summarizes failures.
+    The file name is prefixed with `zz_` to make this plugin be loaded last by
+    Ansible, thus making its output the last thing that users see.
+    '''
+
+    CALLBACK_VERSION = 2.0
+    CALLBACK_TYPE = 'aggregate'
+    CALLBACK_NAME = 'failure_summary'
+    CALLBACK_NEEDS_WHITELIST = False
+
+    def __init__(self):
+        super(CallbackModule, self).__init__()
+        self.__failures = []
+
+    def v2_runner_on_failed(self, result, ignore_errors=False):
+        super(CallbackModule, self).v2_runner_on_failed(result, ignore_errors)
+        self.__failures.append(dict(result=result, ignore_errors=ignore_errors))
+
+    def v2_playbook_on_stats(self, stats):
+        super(CallbackModule, self).v2_playbook_on_stats(stats)
+        # TODO: update condition to consider a host var or env var to
+        # enable/disable the summary, so that we can control the output from a
+        # play.
+        if self.__failures:
+            self._print_failure_summary()
+
+    def _print_failure_summary(self):
+        '''Print a summary of failed tasks (including ignored failures).'''
+        self._display.display(u'\nFailure summary:\n')
+
+        # TODO: group failures by host or by task. If grouped by host, it is
+        # easy to see all problems of a given host. If grouped by task, it is
+        # easy to see what hosts needs the same fix.
+
+        width = len(str(len(self.__failures)))
+        initial_indent_format = u'  {{:>{width}}}. '.format(width=width)
+        initial_indent_len = len(initial_indent_format.format(0))
+        subsequent_indent = u' ' * initial_indent_len
+        subsequent_extra_indent = u' ' * (initial_indent_len + 10)
+
+        for i, failure in enumerate(self.__failures, 1):
+            lines = _format_failure(failure)
+            self._display.display(u'\n{}{}'.format(initial_indent_format.format(i), lines[0]))
+            for line in lines[1:]:
+                line = line.replace(u'\n', u'\n' + subsequent_extra_indent)
+                indented = u'{}{}'.format(subsequent_indent, line)
+                self._display.display(indented)
+
+
+# Reason: disable pylint protected-access because we need to access _*
+#         attributes of a task result to implement this method.
+# Status: permanently disabled unless Ansible's API changes.
+# pylint: disable=protected-access
+def _format_failure(failure):
+    '''Return a list of pretty-formatted lines describing a failure, including
+    relevant information about it. Line separators are not included.'''
+    result = failure['result']
+    host = result._host.get_name()
+    play = _get_play(result._task)
+    if play:
+        play = play.get_name()
+    task = result._task.get_name()
+    msg = result._result.get('msg', u'???')
+    rows = (
+        (u'Host', host),
+        (u'Play', play),
+        (u'Task', task),
+        (u'Message', stringc(msg, C.COLOR_ERROR)),
+    )
+    if 'checks' in result._result:
+        rows += ((u'Details', stringc(pformat(result._result['checks']), C.COLOR_ERROR)),)
+    row_format = '{:10}{}'
+    return [row_format.format(header + u':', body) for header, body in rows]
+
+
+# Reason: disable pylint protected-access because we need to access _*
+#         attributes of obj to implement this function.
+#         This is inspired by ansible.playbook.base.Base.dump_me.
+# Status: permanently disabled unless Ansible's API changes.
+# pylint: disable=protected-access
+def _get_play(obj):
+    '''Given a task or block, recursively tries to find its parent play.'''
+    if hasattr(obj, '_play'):
+        return obj._play
+    if getattr(obj, '_parent'):
+        return _get_play(obj._parent)