The release of HDP 2.3.4 offers a newer version of the ATS which is version 1.5. Part of configuring this new ATS version includes providing the following property if Tez is used:
<description>Plugins that can translate a timeline entity read request into a list of timeline cache ids, separated by commas. </description>
If this property is included but the tez-client is not present, a message will be seen in the ATS log stating ClassNotFound and the ATS server will fail shortly after issuing a startup.
The full documentation for configuring ATS 1.5 is located here: