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, 57 insertions, 0 deletions

diff --git a/roles/openshift_health_checker/openshift_checks/__init__.py b/roles/openshift_health_checker/openshift_checks/__init__.py
new file mode 100644
index 000000000..d893ba591
--- /dev/null
+++ b/roles/openshift_health_checker/openshift_checks/__init__.py
@@ -0,0 +1,57 @@
+"""
+Health checks for OpenShift clusters.
+"""
+
+import os
+from abc import ABCMeta, abstractmethod, abstractproperty
+from importlib import import_module
+
+import six
+
+
+class OpenShiftCheckException(Exception):
+    """Raised when a check cannot proceed."""
+    pass
+
+
+@six.add_metaclass(ABCMeta)
+class OpenShiftCheck(object):
+    """A base class for defining checks for an OpenShift cluster environment."""
+
+    def __init__(self, module_executor):
+        self.module_executor = module_executor
+
+    @abstractproperty
+    def name(self):
+        """The name of this check, usually derived from the class name."""
+        return "openshift_check"
+
+    @classmethod
+    def is_active(cls, task_vars):  # pylint: disable=unused-argument
+        """Returns true if this check applies to the ansible-playbook run."""
+        return True
+
+    @abstractmethod
+    def run(self, tmp, task_vars):
+        """Executes a check, normally implemented as a module."""
+        return {}
+
+    @classmethod
+    def subclasses(cls):
+        """Returns a generator of subclasses of this class and its subclasses."""
+        for subclass in cls.__subclasses__():  # pylint: disable=no-member
+            yield subclass
+            for subclass in subclass.subclasses():
+                yield subclass
+
+
+# Dynamically import all submodules for the side effect of loading checks.
+
+EXCLUDES = (
+    "__init__.py",
+    "mixins.py",
+)
+
+for name in os.listdir(os.path.dirname(__file__)):
+    if name.endswith(".py") and name not in EXCLUDES:
+        import_module(__package__ + "." + name[:-3])