[GitHub] flink issue #3286: [FLINK-1579] [WIP] Implement Standalone HistoryServer

[uce <gi...@git.apache.org>]

Github user uce commented on the issue:

    https://github.com/apache/flink/pull/3286
  
    Thanks for this PR. I think it's super cool (and long overdue) to finally have this. I think the general approach is sound and has good things going for it.
    
    But I see two problems with maintaining the current implementation in the long run:
    - Changing a URL in the web dashboard requires that we also change it in the history server file generation. It's easy to accidentally break the history server and it's cumbersome to write tests when we extend it.
    - We have all JSON generation in the JsonUtil. That results in a giant class (as you say) that is really tightly coupled to the handlers but resides in a different place.
    
    I think we can word around this by moving the archival logic to the handlers. I think it's fair that handlers that want to take part in historical archiving implement their archival logic on their own. The handlers would need to return their path and also their JSON. That way we keep all the handler logic in one place for both the regular frontend and history server. A "historic execution graph" might be a simple collection of `path, JSON` entries that the history server persists on receive.
    
    Another minor thing is that the final status of the operators is missing on the history server. I don't know whether that is a front end issue or something is missing in the JSON.
    
    I think it's best to close this PR for now and think about how we want to extend this a bit for better maintainability.


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