add docker storage check

roles/openshift_health_checker/openshift_checks/docker_storage_check.py

@@ -0,0 +1,41 @@
+# pylint: disable=missing-docstring
+from openshift_checks import OpenShiftCheck, get_var
+
+
+class DockerStorageCheck(OpenShiftCheck):
+    """Check Docker storage sanity.
+
+    This check ensures that Docker is using the devicemapper
+    storage driver, that thinpool usage is not close to 100%,
+    and that Loopback is not being used.
+    """
+
+    name = "docker_storage_check"
+    tags = ["preflight"]
+
+    def run(self, tmp, task_vars):
+        info = self.module_executor("docker_info", {}, task_vars).get("info", {})
+
+        if not self.is_devicemapper_used(info):
+            msg = "Unsupported Docker storage driver detected. Only \"devicemapper\" is currently supported."
+            return {"failed": True, "msg": msg}
+
+        if self.is_using_loopback_device(info):
+            msg = "Use of loopback devices is discouraged. Try running Docker with `--storage-opt dm.thinpooldev`"
+            return {"failed": True, "msg": msg}
+
+        return {"failed": True, "msg": "%s" % info.get("Data Space Available")}
+
+        return {"changed": False}
+
+    @staticmethod
+    def is_devicemapper_used(docker_info):
+        return docker_info.get("Driver", None) == "devicemapper"
+
+    @staticmethod
+    def is_using_loopback_device(info):
+        for status in info.get("DriverStatus"):
+            if status[0] == "Data loop file":
+                return bool(status[1])
+
+        return False