[GitHub] uce opened a new pull request #7717: [FLINK-11533] [container] Add option parse JAR manifest for jobClassName

[GitBox <gi...@apache.org>]

uce opened a new pull request #7717: [FLINK-11533] [container] Add option parse JAR manifest for jobClassName
URL: https://github.com/apache/flink/pull/7717
 
 
   ## What is the purpose of the change
   
   This PR allows users to point the `StandaloneJobClusterEntryPoint` to a JAR file instead of requiring a job class name of the job to execute.
   
   Users can provide the argument as follows: `--job-classname from-jar:/foo/bar.jar` and let the entry point parse the JAR manifest for the entry class. The prefix is not a valid class name and should not conflict with existing usage of this option.
   
   The original plan in the ticket was to add an additional command line argument like `--job-jar` but that seemed confusing as the JAR would only be used to parse the job class name. Also, an additional argument would have made the entry point argument validation slightly more complex (e.g. both `--job-classname` and `--job-jar` would be optional, but exactly one of the two required).
   
   I think the current approach is a step into the right direction. Eventually, I think there is a case to be made for having a `--job-jar` argument that actually distributes the user JAR between the cluster components (with proper distribution of blobs, setup of the user class loader, etc.) instead of requiring it to be on the class path.
   
   ## Brief change log
   
   - Add `JarManifestParser` utility
   - Check `PackagedProgram.MANIFEST_ATTRIBUTE_ASSEMBLER_CLASS`, `PackagedProgram.MANIFEST_ATTRIBUTE_MAIN_CLASS` manifest attributes if `job-classname` starts with `from-jar:`
   
   ## Verifying this change
   
   - This change added unit tests
   - Additionally, a test JAR assembly step has been added to test the new functionality with a proper job jar
   
   ## Does this pull request potentially affect one of the following parts:
   
     - Dependencies (does it add or upgrade a dependency): no
     - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: **yes** (adds special case behavior of command line argument `--job-classname`)
     - The serializers: no
     - The runtime per-record code paths (performance sensitive): no
     - Anything that affects deployment or recovery: no
     - The S3 file system connector: no
   
   ## Documentation
   
   - Updated command line argument help page
   - Added note to Kubernetes template README
   

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