It seems that there is a problem in publish_ui_logs_to_swift workflow:

Failed to handle action completion [error=Can not evaluate YAQL expression [expression=task().result.select($._id), error=u'_id', data={}]


(undercloud) [stack@undercloud-0 ~]$ openstack workflow execution output show c25f375e-116f-42a1-b561-5e64006e1811
{
    "result": "Failed to handle action completion [error=Can not evaluate YAQL expression [expression=task().result.select($._id), error=u'_id', data={}], wf=tripleo.plan_management.v1.publish_ui_logs_to_swift, task=get_messages, action=zaqar.claim_messages]:\nTraceback (most recent call last):\n  File \"/usr/lib/python2.7/site-packages/mistral/engine/task_handler.py\", line 110, in _on_action_complete\n    task.on_action_complete(action_ex)\n  File \"/usr/lib/python2.7/site-packages/osprofiler/profiler.py\", line 159, in wrapper\n    result = f(*args, **kwargs)\n  File \"/usr/lib/python2.7/site-packages/mistral/engine/tasks.py\", line 381, in on_action_complete\n    self.complete(state, state_info)\n  File \"/usr/lib/python2.7/site-packages/osprofiler/profiler.py\", line 159, in wrapper\n    result = f(*args, **kwargs)\n  File \"/usr/lib/python2.7/site-packages/mistral/engine/tasks.py\", line 221, in complete\n    data_flow.publish_variables(self.task_ex, self.task_spec)\n  File \"/usr/lib/python2.7/site-packages/mistral/workflow/data_flow.py\", line 215, in publish_variables\n    task_ex.published = expr.evaluate_recursively(branch_vars, expr_ctx)\n  File \"/usr/lib/python2.7/site-packages/mistral/expressions/__init__.py\", line 100, in evaluate_recursively\n    data[key] = _evaluate_item(data[key], context)\n  File \"/usr/lib/python2.7/site-packages/mistral/expressions/__init__.py\", line 79, in _evaluate_item\n    return evaluate(item, context)\n  File \"/usr/lib/python2.7/site-packages/mistral/expressions/__init__.py\", line 71, in evaluate\n    return evaluator.evaluate(expression, context)\n  File \"/usr/lib/python2.7/site-packages/mistral/expressions/yaql_expression.py\", line 159, in evaluate\n    cls).evaluate(trim_expr, data_context)\n  File \"/usr/lib/python2.7/site-packages/mistral/expressions/yaql_expression.py\", line 113, in evaluate\n    \", data=%s]\" % (expression, str(e), data_context)\nYaqlEvaluationException: Can not evaluate YAQL expression [expression=task().result.select($._id), error=u'_id', data={}]\n"
}

By looking at the error message, It seems that the failing expression does not handle the case when there are no messages?

Running:

    $ mistral execution-create tripleo.plan_management.v1.publish_ui_logs_to_swift

Works fine for me on a recent tripleo master install

Is the `tripleo` queue present in the output of

    $ openstack messaging queue list

?

This is the get_messages task from the error message above:

      get_messages:
        action: zaqar.claim_messages
        on-success:
          - format_messages: <% task().result.len() > 0 %>
        input:
          queue_name: <% $.logging_queue_name %>
          ttl: 60
          grace: 60
        publish:
          status: SUCCESS
          messages: <% task().result %>
          message_ids: <% task().result.select($._id) %>

It says that the "task().result.select($._id)" failed to run.  Yes, this does suggest that the action failed.

On my setup, the "logging_queue_name" queue ("tripleo-ui-logging" by default) is not present.  This workflow still finishes fine.

Note that my environment doesn't yet have any tripleo-ui messages because I'm currently unable to log in due this bug[1].

[1]: https://bugs.launchpad.net/tripleo/+bug/1801778

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Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2019:0446