[YARN-8624] Cleanup ENTRYPOINT documentation

• Type: Sub-task
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.2.0, 3.1.2
• Labels: Docker
• Target Version/s: 3.2.0
• Assignee: Craig Condit
• Reporter: Craig Condit
• Created: 03/Aug/18 13:39
• Updated: 06/Aug/18 17:01
• Resolved: 06/Aug/18 16:40

Description

With the changes to allow disabling the YARN launch script in favor of running whatever is specified in the image, I think the following needs to be remove/updated. There is already a section called Docker Container ENTRYPOINT support. I think we can clean this up a bit make it easier to understand this feature. This will likely require some testing to fully describe the feature.

If a Docker image has a command set, the behavior will depend on whether the YARN_CONTAINER_RUNTIME_DOCKER_RUN_OVERRIDE_DISABLE is set to true. If so, the command will be overridden when LCE launches the image with YARN's container launch script. 
 If a Docker image has an entry point set, the entry point will be honored, but the default command may be overridden, as just mentioned above. Unless the entry point is something similar to sh -c or YARN_CONTAINER_RUNTIME_DOCKER_RUN_OVERRIDE_DISABLE is set to true, the net result will likely be undesirable. Because the YARN container launch script is required to correctly launch the YARN task, use of entry points is discouraged. 

Issue Links

• is related to: YARN-8287 Update documentation and yarn-default related to the Docker runtime