:original_name: mrs_01_2074.html

.. _mrs_01_2074:

Error Occurs When a User Switches to the Tez Web UI
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Question
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When a user logs in to Manager and switches to the Tez web UI, error 404 or 503 is displayed.

|image1|

|image2|

Answer
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The Tez web UI depends on the TimelineServer instance of Yarn. Therefore, TimelineServer must be installed in advance and in the **Good** state.

.. |image1| image:: /_static/images/en-us_image_0000001389429344.png
.. |image2| image:: /_static/images/en-us_image_0000001388394084.png
