GitHub user Ziemin opened a pull request:

    https://github.com/apache/incubator-predictionio/pull/295

    [PIO-30] Set up a cross build for Scala 2.10 (Spark 1.6.2) and Scala …

    This PR introduces a simple profile-based build of PredictionIO, which 
comes along with some upgrades including a new version of Spark. 
    
    ### The key changes include:
    
    * build.sbt - here I created two profiles with different sets of artifacts 
to be included. Their names are _scala-2.11_  and _scala-2.10_, where the 
former is chosen by default. In order to set a desired profile for sbt command 
`-Dbuild.profile=<profile_name>` property has to be provided. 
    You can print the description of some profile by e.g. 
    ```sbt -Dbuild.profile=scala-2.10 printProfile```
    The _scala-2.11_ settings include Spark version 2.0.0, while _scala-2.11_ 
sets it to 1.6.2. This can be configured, by adding a dedicated property:
    ``` sbt -Dbuild.profile=scala-2.11 -Dspark.version=1.6.0 -D 
Dhadoop.version=2.6.4 <sbt task> ```
    This command will set a build profile to _scala-2.11_, but will use a 
different versions of Spark and Hadoop. It makes the configuration more 
flexible, especially if someone wants to build the project according to their 
own needs. 
    Very important thing to note is that versions of spark before 1.6.x are no 
longer supported and scala 2.10.x is deprecated. 
    
    * 
`data/src/main/spark-1/org/apache/predictionio/data/SparkVersionDependent.scala`
 and 
`data/src/main/spark-2/org/apache/predictionio/data/SparkVersionDependent.scala`
 - are the only examples of version dependent code. They are solely for 
providing a proper type of an object for Spark sql related actions. Sbt is 
configured to include version specific source paths like these.
    
    * make_distribution.sh - in order to create an archive for Scala 2.10 one 
has to provide it with an argument in the same way as sbt 
(./make_distribution.sh -Dbuild.profile=scala-2.10). By default it will build 
for _scala-2.11_.
    
    * integration tests - The docker image is updated, I pushed it with a tag 
spark_2.0.0 not to interfere with the current build. It contains both versions 
of Spark and on startup sets up environment according to dependencies that 
predictionIO was built with. It uses a simple Java program 
`tests/docker-files/BuildInfoPrinter.java` linked with the assembly of 
PredictionIO to acquire necessary information. Travis CI makes use of the setup 
and runs 8 parallel builds, the number doubled because of introducing two 
different build profiles.
    
    I also noticed that there are many places hardcoding different version 
numbers and links to packages to be downloaded. Maintaining the project and 
keeping everything consistent gets only more difficult, therefore I came up 
with a few small scripts getting proper versions of dependencies from the build 
config and setting some variables accordingly. An example is `conf/vendors.sh`, 
which provided that some variables are set (e.g. by `dev/set-build-profile.sh`) 
initializes some other useful variables, i.e. `SPARK_DOWNLOAD, SPARK_ARCHIVE, 
SPARK_DIRNAME`. They are used in travis configuration as well as in the 
Dockerfile, which now should be built with a dedicated script 
`tests/docker-build.sh`. Such approach makes it easier to keep everything 
coherent while bumping version numbers.
    
    ### Some problems encountered during upgrade
    Updating Spark caused some troubles
    
    * The classpath has to be extended to run the unit tests successfully for 
some sub-packages. (see `build.sbt`)
    * Column names have to be handled differently for Postgres in JDBCPevents, 
as Spark surrounds them with "..." what breaks the current schema in this case
    * `tests/pio_tests/utils.py` - has a special Spark pass through argument to 
set `spark.sql.warehouse.dir`, because the defaults cause runtime exceptions. 
See -> 
[here](https://mail-archives.apache.org/mod_mbox/spark-user/201608.mbox/%3ccamassd+efz+uscmnzvkfp00qbr9ynv8lrfhvz9lrmnwh2vk...@mail.gmail.com%3E)


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

    $ git pull https://github.com/Ziemin/incubator-predictionio upgrade

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

    https://github.com/apache/incubator-predictionio/pull/295.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 #295
    
----
commit 39879f04639b123510f0668e0de7b33fd7418784
Author: Marcin Ziemiński <ziem...@gmail.com>
Date:   2016-08-09T21:20:54Z

    [PIO-30] Set up a cross build for Scala 2.10 (Spark 1.6.2) and Scala 2.11
    (Spark 2.0.0).
    
    Changes also include updating travis integration tests, which run now
    eight parallel builds.

----


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