add docker storage driver check

roles/openshift_health_checker/openshift_checks/docker_storage_driver_check.py

@@ -0,0 +1,48 @@
+# pylint: disable=missing-docstring
+from openshift_checks import OpenShiftCheck, get_var
+
+
+class DockerStorageDriverCheck(OpenShiftCheck):
+    """Check Docker storage driver compatibility.
+
+    This check ensures that Docker is using a supported storage driver,
+    and that Loopback is not being used (if using devicemapper).
+    """
+
+    name = "docker_storage_driver_check"
+    tags = ["preflight"]
+
+    storage_drivers = ["devicemapper", "overlay2"]
+
+    def run(self, tmp, task_vars):
+        is_containerized = get_var(task_vars, "openshift", "common", "is_containerized")
+        if not is_containerized:
+            return {"changed": False}
+
+        info = self.execute_module("docker_info", {}, task_vars).get("info", {})
+
+        if not self.is_supported_storage_driver(info):
+            msg = "Unsupported Docker storage driver detected. Supported storage drivers: {drivers}"
+            return {"failed": True, "msg": msg.format(drivers=self.storage_drivers)}
+
+        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 {"changed": False}
+
+    def is_supported_storage_driver(self, docker_info):
+        return docker_info.get("Driver", "") in self.storage_drivers
+
+    @staticmethod
+    def is_using_loopback_device(docker_info):
+        # Loopback device usage is only an issue if using devicemapper.
+        # Skip this check if using any other storage driver.
+        if docker_info.get("Driver", "") != "devicemapper":
+            return False
+
+        for status in docker_info.get("DriverStatus", []):
+            if status[0] == "Data loop file":
+                return bool(status[1])
+
+        return False