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From Garrett Barton <garrett.bar...@gmail.com>
Subject Classpath/ClassLoader issues
Date Mon, 18 Sep 2017 16:42:43 GMT
Hey all,

 I am trying out a POC with flink on yarn.  My simple goal is to read from
a Hive ORC table, process some data and write to a new Hive ORC table.

Currently I can get Flink to read the source table fine, both with using
The HCatalog Input format directly, and by using the flink-hcatalog
wrapper.  Processing the data also works fine. Dumping to console or a text
file also works fine.

I'm now stuck trying to write the data out, I'm getting

Caused by: java.lang.ClassNotFoundException: org.apache.hadoop.hive.ql.io.
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
at org.apache.hadoop.hive.common.JavaUtils.loadClass(JavaUtils.java:78)
at org.apache.hadoop.hive.common.JavaUtils.loadClass(JavaUtils.74)
at org.apache.hive.hcatalog.mapreduce.FosterStorageHandler.<init>(
at org.apache.hive.hcatalog.common.HCatUtil.getStorageHandler(HCatUtil.

Since I read from an Orc table, I know I have that class in my classpath.
So I'm wondering if each stage/step in a flink process has some kind of
special classloader that I am not aware of?  (also its odd that it wants
the inputformat and not the outputformat, not sure why yet)

My output code looks like this:

Job job = Job.getInstance(conf);

HCatOutputFormat.setOutput(job, OutputJobInfo.create("schema",
HCatSchema outSchema = HCatOutputFormat.getTableSchema(job.
HCatOutputFormat.setSchema(job.getConfiguration(), outSchema);

HCatOutputFormat outputFormat = new HCatOutputFormat();

HadoopOutputFormat<NullWritable, DefaultHCatRecord> out = new
HadoopOutputFormat(outputFormat, job);

// from previous processing step

One other thing to note, I had to put flink-hadoop-compatability_2.11-1.3.2.jar
into the lib folder of the flink distro.  Building my code in a shaded jar
with that dependency did not work for me.  However when I put the hive/hcat
jars in the lib folder it caused lots of other errors.  Since the shading
didn't work for the hadoop-compatability jar it makes me think there is
some funky class loader stuff going on.  I don't understand why this doesnt
work.  The orc code is shaded and verified in my jar, the classes are
present, plus I successfully read from an ORC table.

Any help or explanation into how the classpath/classloading works would be

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