GitHub user JoshRosen opened a pull request:

    https://github.com/apache/spark/pull/2852

    [WIP] Add WebUITableBuilder to simplify table-building code

    This work-in-progress commit illustrates a weekend hack project that I came 
up with for significantly simplifying the web UI's table rendering code.  See 
the huge block comment in `WebUITableBuilder` for more details.  This isn't 
ready to merge yet; I wanted to get some feedback before converting the rest of 
the table construction code to use this (I know that I should open a JIRA for 
this, too; I'll do it tomorrow).
    
    Essentially, this commit adds a small builder class for constructing 
objects that know how to render web UI tables.  This builder helps us to avoid 
several sources of errors / maintenance headaches, such as 
duplicate/boilerplate markup, inconsistent formatting of columns in different 
tables (e.g. durations or memory being displayed differently), separation of 
column names from column data values, etc.  This is best illustrated by some 
sample code; this new framework lets you write
    
    ```scala
      private val appTable: UITable[ApplicationInfo] = {
        val builder = new UITableBuilder[ApplicationInfo]()
        import builder._
        customCol("ID") { app =>
          <a href={"app?appId=" + app.id}>{app.id}</a>
        }
        col("Name") { _.id }
        intCol("Cores") { _.coresGranted }
        memCol("Memory per Node") { _.desc.memoryPerSlave }
        dateCol("Submitted Time") { _.submitDate }
        col("User") { _.desc.user }
        col("State") { _.state.toString }
        durationCol("Duration") { _.duration }
        build
      }
    ```
    
    to render the "applications" table in the standalone Master UI.  I find 
this significantly easier to understand and maintain than the old code.  For 
example, this makes it trivial to re-order columns.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/JoshRosen/spark webui-table-builder

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/spark/pull/2852.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #2852
    
----
commit c0aca09d676ce750496451f3691c5f9e861103bd
Author: Josh Rosen <joshro...@databricks.com>
Date:   2014-10-20T06:02:29Z

    Add WebUITableBuilder to clean up table building code.
    
    This significantly simplifies / abstracts the web UI's table construction
    code, which seems to account for the majority of the UI code.  I haven't
    converted all tables to use this yet; this commit just provides the basic
    framework and a few example usages in the master web UI.

----


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