symptom

2021-10-08 17:54:36.846 - [BASIC] mongodb_input - To convert the start of the release patch  [mongodb_input]
2021-10-08 17:54:36.986 - [ERROR] MongoDB input.0 - ERROR (version 8.3.0.0-371, build 8.3.0.0-371 from 2019-06-11 11.09.08 by buildguy) : Can't run transformation due to plugin missing
2021-10-08 17:54:36.986 - [ERROR] MongoDB input.0 - ERROR (version 8.3.0.0-371, build 8.3.0.0-371 from 2019-06-11 11.09.08 by buildguy) : Error initialization steps[MongoDB input]
2021-10-08 17:54:36.986 - [ERROR] mongodb_input - ERROR (version 8.3.0.0-371, build 8.3.0.0-371 from 2019-06-11 11.09.08 by buildguy) : Step [MongoDB input.0] Initialization failed!
2021-10-08 17:54:36.986 - [ERROR] mongodb_input - ERROR (version 8.3.0.0-371, build 8.3.0.0-371 from 2019-06-11 11.09.08 by buildguy) : Error detected!

Solution:

Copy the two directories under the data integration \ system \ karaf \ system \ pentaho directory to the kettle pack/plugins directory

pentaho-mongodb-plugin

pentaho-mongo-utils

Add dependency to project:

 <dependency>
     <groupId>pentaho</groupId>
     <artifactId>pentaho-mongodb-plugin</artifactId>
     <version>${kettle.version}</version>
 </dependency>
 <dependency>
     <groupId>pentaho</groupId>
     <artifactId>pentaho-mongo-utils</artifactId>
     <version>${kettle.version}</version>
 </dependency>

Or directly copy the above dependent jar packages to the kettle pack/Tomcat/lib directory