add fluentd logging driver config check

roles/openshift_health_checker/openshift_checks/logging/fluentd.py

@@ -35,9 +35,72 @@ def run(self, tmp, task_vars):
                    "{}".format(check_error))
             return {"failed": True, "changed": False, "msg": msg}
 
+        config_error = self.check_logging_config(fluentd_pods, task_vars)
+        if config_error:
+            msg = ("The following Fluentd logging configuration issue was found:"
+                   "\n-------\n"
+                   "{}".format(config_error))
+            return {"failed": True, "changed": False, "msg": msg}
+
         # TODO(lmeyer): run it all again for the ops cluster
         return {"failed": False, "changed": False, "msg": 'No problems found with Fluentd deployment.'}
 
+    def check_logging_config(self, fluentd_pods, task_vars):
+        """Ensure that the configured Docker logging driver matches fluentd settings.
+        This means that, at least for now, if the following condition is met:
+
+            openshift_logging_fluentd_use_journal == True
+
+        then the value of the configured Docker logging driver should be "journald".
+        Otherwise, the value of the Docker logging driver should be "json-file".
+        Returns an error string if the above condition is not met, or None otherwise."""
+
+        pod_name = fluentd_pods[0]["metadata"]["name"]
+        use_journald = self._exec_oc("exec {} /bin/printenv USE_JOURNAL".format(pod_name), [], task_vars)
+
+        docker_info = self.execute_module("docker_info", {}, task_vars)
+        if not docker_info.get("info", False):
+            return "No information was returned by the Docker client. Unable to verify the logging driver in use."
+
+        if not docker_info["info"].get("LoggingDriver", False):
+            return "No logging driver information was returned by the Docker client."
+
+        logging_driver = docker_info["info"]["LoggingDriver"]
+        recommended_logging_driver = "journald"
+        error = None
+
+        # If fluentd is set to use journald but Docker is not, recommend setting the `--log-driver`
+        # option as an inventory file variable, or adding the log driver value as part of the
+        # Docker configuration in /etc/docker/daemon.json. There is no global --log-driver flag that
+        # can be passed to the Docker binary; the only other recommendation that can be made, would be
+        # to pass the `--log-driver` flag to the "run" sub-command of the `docker` binary when running
+        # individual containers.
+        if use_journald and logging_driver != "journald":
+            error = ('Your Fluentd configuration is set to aggregate Docker container logs from "journald".\n'
+                     'This differs from your Docker configuration, which has been set to use "{driver}" '
+                     'as the default method of storing logs.\n'
+                     'This discrepancy in configuration will prevent Fluentd from receiving any logs'
+                     'from your Docker containers.\n').format(driver=logging_driver)
+        elif not use_journald and logging_driver != "json-file":
+            recommended_logging_driver = "json-file"
+            error = ('Your Fluentd configuration is set to aggregate Docker container logs from '
+                     'individual json log files per container.\n '
+                     'This differs from your Docker configuration, which has been set to use '
+                     '"{driver}" as the default method of storing logs.\n'
+                     'This discrepancy in configuration will prevent Fluentd from receiving any logs'
+                     'from your Docker containers.\n').format(driver=logging_driver)
+
+        if error:
+            error += ('To resolve this issue, add the following variable to your Ansible inventory file:\n\n'
+                      '  openshift_docker_options="--log-driver={driver}"\n\n'
+                      'Alternatively, you can add the following option to your Docker configuration, located in'
+                      '"/etc/docker/daemon.json":\n\n'
+                      '{{ "log-driver": "{driver}" }}\n\n'
+                      'See https://docs.docker.com/engine/admin/logging/json-file '
+                      'for more information.').format(driver=recommended_logging_driver)
+
+        return error
+
     @staticmethod
     def _filter_fluentd_labeled_nodes(nodes_by_name, node_selector):
         """Filter to all nodes with fluentd label. Returns dict(name: node), error string"""