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From Fabian Hueske <fhue...@gmail.com>
Subject Re: Classpath/ClassLoader issues
Date Wed, 20 Sep 2017 14:15:53 GMT
Hi Garrett,

I think I identified the problem.
You said you put the Hive/HCat dependencies into your user fat Jar,
correct? In this case, they are loaded with Flink's userClassLoader (as
described before).

In the OutputFormatVertex.finalizeOnMaster() method, Flink correctly loads
the user classes with the user class loader.
However, when the HCatOutputFormat.getOutputCommitter() method is called,
Hive tries to load additional classes with the current thread class loader
(see at org.apache.hadoop.hive.common.JavaUtils.loadClass(JavaUtils.
java:78)).
This behavior is actually OK, because we usually set the context
classloader to be the user classloader before calling user code. However,
this has not been done here.
So, this is in fact a bug.

I created this JIRA issue: https://issues.apache.org/jira/browse/FLINK-7656
and will open a PR for that.

Thanks for helping to diagnose the issue,
Fabian

2017-09-19 22:05 GMT+02:00 Garrett Barton <garrett.barton@gmail.com>:

> Fabian,
>
>  It looks like hive instantiates both input and output formats when doing
> either. I use hive 1.2.1, and you can see in HCatUtil.getStorageHandler
> where it tries to load both.  It looks like its happening after the writes
> complete and flink is in the finish/finalize stage.  When I watch the
> counters in the Flink ui, i see all output tasks mark finished along with
> bytes sent and records sent being exactly what I expect them to be.  The
> first error also mentions the master, is this the flink jobmanager process
> then?
>
> The expanded stacktrace is:
>
> Caused by: java.lang.Exception: Failed to finalize execution on master
> at org.apache.flink.runtime.executiongraph.ExecutionGraph.
> vertexFinished(ExecutionGraph.java:1325)
> at org.apache.flink.runtime.executiongraph.ExecutionVertex.
> executionFinished(ExecutionVertex.java:688)
> at org.apache.flink.runtime.executiongraph.Execution.
> markFinished(Execution.java:797)
> at org.apache.flink.runtime.executiongraph.ExecutionGraph.
> updateState(ExecutionGraph.java:1477)
> at org.apache.flink.runtime.jobmanager.JobManager$$
> anonfun$handleMessage$1$$anonfun$applyOrElse$4.apply$
> mcV$sp(JobManager.scala:710)
> at org.apache.flink.runtime.jobmanager.JobManager$$
> anonfun$handleMessage$1$$anonfun$applyOrElse$4.apply(JobManager.scala:709)
> at org.apache.flink.runtime.jobmanager.JobManager$$
> anonfun$handleMessage$1$$anonfun$applyOrElse$4.apply(JobManager.scala:709)
> ... 8 more
> Caused by: java.lang.RuntimeException: java.io.IOException: Failed to load
> foster storage handler
> at org.apache.flink.api.java.hadoop.mapreduce.HadoopOutputFormatBase.
> finalizeGlobal(HadoopOutputFormatBase.java:202)
> at org.apache.flink.runtime.jobgraph.OutputFormatVertex.finalizeOnMaster(
> OutputFormatVertex.java:118)
> at org.apache.flink.runtime.executiongraph.ExecutionGraph.
> vertexFinished(ExecutionGraph.java:1320)
> ... 14 more
> Caused by: java.io.IOException: Failed to load foster storage handler
> at org.apache.hive.hcatalog.common.HCatUtil.getStorageHandler(HCatUtil.
> java:409)
> at org.apache.hive.hcatalog.common.HCatUtil.getStorageHandler(HCatUtil.
> java:367)
> at org.apache.hive.hcatalog.mapreduce.HCatBaseOutputFormat.
> getOutputFormat(HCatBaseOutputFormat.java:77)
> at org.apache.hive.hcatalog.mapreduce.HCatOutputFormat.getOutputCommitter(
> HCatOutputFormat.java:275)
> at org.apache.flink.api.java.hadoop.mapreduce.HadoopOutputFormatBase.
> finalizeGlobal(HadoopOutputFormatBase.java:200)
> ... 16 more
> Caused by: java.lang.ClassNotFoundException: org.apache.hadoop.hive.ql.io
> .orc.OrcInputFormat
> at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
> at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
> at sun.misc.Launcher$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.<ini
> t>(FosterStorageHandler.68)
> at org.apache.hive.hcatalog.common.HCatUtil.getStorageHandler(H
> CatUtil.java:404)
>
>
> Thank you all for any help. :)
>
> On Tue, Sep 19, 2017 at 11:05 AM, Fabian Hueske <fhueske@gmail.com> wrote:
>
>> Hi Garrett,
>>
>> Flink distinguishes between two classloaders: 1) the system classloader
>> which is the main classloader of the process. This classloader loads all
>> jars in the ./lib folder and 2) the user classloader which loads the job
>> jar.
>> AFAIK, the different operators do not have distinct classloaders. So, in
>> principle all operators should use the same user classloader.
>>
>> According to the stacktrace you posted, the OrcInputFormat cannot be
>> found when you try to emit to an ORC file.
>> This looks suspicious because I would rather expect the OrcOutputFormat
>> to be the problem than the input format.
>> Can you post more of the stacktrace? This would help to identify the spot
>> in the Flink code where the exception is thrown.
>>
>> Thanks, Fabian
>>
>> 2017-09-18 18:42 GMT+02:00 Garrett Barton <garrett.barton@gmail.com>:
>>
>>> 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
>>> ClassNotFoundExceptions:
>>>
>>> Caused by: java.lang.ClassNotFoundException:
>>> org.apache.hadoop.hive.ql.io.orc.OrcInputFormat
>>> 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.<ini
>>> t>(FosterStorageHandler.68)
>>> at org.apache.hive.hcatalog.common.HCatUtil.getStorageHandler(H
>>> CatUtil.java:404)
>>>
>>> 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",
>>> "table",null));
>>> HCatSchema outSchema = HCatOutputFormat.getTableSchem
>>> a(job.getConfiguration());
>>> HCatOutputFormat.setSchema(job.getConfiguration(), outSchema);
>>>
>>> HCatOutputFormat outputFormat = new HCatOutputFormat();
>>>
>>> HadoopOutputFormat<NullWritable, DefaultHCatRecord> out = new
>>> HadoopOutputFormat(outputFormat, job);
>>>
>>> // from previous processing step
>>> hcat.output(out);
>>> env.execute("run");
>>>
>>>
>>>
>>> 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 wonderful!
>>>
>>
>>
>

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