OLAP traversals do not work with JanusGraph 0.5.2 and BigTable

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JanusGraph Version: 0.5.2
Storage Backend: Google Cloud BigTable

### Steps to reproduce:

Configure JanusGraph to perform an OLAP traversals on a graph persisted in HBase using Spark in YARN mode:

``read-hbase-spark-yarn.properties``

```
#
# Hadoop Graph Configuration
#
gremlin.graph=org.apache.tinkerpop.gremlin.hadoop.structure.HadoopGraph
gremlin.hadoop.graphReader=org.janusgraph.hadoop.formats.hbase.HBaseInputFormat
gremlin.hadoop.graphWriter=org.apache.hadoop.mapreduce.lib.output.NullOutputFormat

gremlin.hadoop.jarsInDistributedCache=true
gremlin.hadoop.inputLocation=none
gremlin.hadoop.outputLocation=output

gremlin.spark.persistContext=true

#
# JanusGraph HBase InputFormat configuration
#
janusgraphmr.ioformat.conf.storage.backend=hbase
janusgraphmr.ioformat.conf.storage.hbase.ext.google.bigtable.instance.id=janusgraph
janusgraphmr.ioformat.conf.storage.hbase.ext.google.bigtable.project.id=some-project-id
janusgraphmr.ioformat.conf.storage.hbase.ext.hbase.client.connection.impl=com.google.cloud.bigtable.hbase2_x.BigtableConnection

#
# SparkGraphComputer with YARN Configuration
#

spark.master=yarn
spark.executor.memory=1g
spark.serializer=org.apache.tinkerpop.gremlin.spark.structure.io.gryo.GryoSerializer
spark.submit.deployMode=client

spark.yarn.archive=/home/adbalici/janusgraph-0.5.2/lib.zip
spark.yarn.appMasterEnv.CLASSPATH=/home/adbalici/hadoop-conf:./lib.zip/*
spark.executor.extraClassPath=/home/adbalici/hadoop-conf:./lib.zip/*
```

``lib.zip`` was created based on this recipe: http://yaaics.blogspot.com/2017/07/configuring-janusgraph-for-spark-yarn.html
Assume the ``CLASSPATH`` and the Hadoop Conf are properly created as the Spark Job is submitted and appears in the YARN Resource Manager.

With all this configured, attempting to run a simple OLAP traversal will result in a ``java.lang.IllegalStateException: java.lang.UnsupportedOperationException: getRegionMetrics`` (see below for the extended stacktrace).

This error comes from ``com.google.cloud.bigtable.hbase2_x.BigtableAdmin`` (https://github.com/googleapis/java-bigtable-hbase/blob/master/bigtable-hbase-2.x-parent/bigtable-hbase-2.x/src/main/java/com/google/cloud/bigtable/hbase2_x/BigtableAdmin.java).

Otherwise, **normal OLTP traversal are working just fine**. I was able to create vertex, delete them, add edges, etc...

```
graph = GraphFactory.open('conf/hadoop-graph/read-hbase-spark-yarn.properties')
g = graph.traversal().withComputer(SparkGraphComputer)
g.V().count()
```

### Stack Trace

```
java.lang.IllegalStateException: java.lang.UnsupportedOperationException: getRegionMetrics
at org.apache.tinkerpop.gremlin.process.computer.traversal.step.map.VertexProgramStep.processNextStart(VertexProgramStep.java:88)
at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:143)
at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.next(ExpandableStepIterator.java:50)
at org.apache.tinkerpop.gremlin.process.computer.traversal.step.map.ComputerResultStep.processNextStart(ComputerResultStep.java:68)
at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:143)
at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.hasNext(DefaultTraversal.java:197)
at org.codehaus.groovy.vmplugin.v7.IndyInterface.selectMethod(IndyInterface.java:234)
at org.apache.tinkerpop.gremlin.console.Console$_closure3.doCall(Console.groovy:255)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:101)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:323)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:263)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1041)
at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:37)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:127)
at org.codehaus.groovy.tools.shell.Groovysh.setLastResult(Groovysh.groovy:463)
at sun.reflect.GeneratedMethodAccessor28.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.runtime.callsite.PlainObjectMetaMethodSite.doInvoke(PlainObjectMetaMethodSite.java:43)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite$PogoCachedMethodSiteNoUnwrapNoCoerce.invoke(PogoMetaMethodSite.java:190)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:58)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:51)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:63)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:168)
at org.codehaus.groovy.tools.shell.Groovysh.execute(Groovysh.groovy:201)
at org.apache.tinkerpop.gremlin.console.GremlinGroovysh.super$3$execute(GremlinGroovysh.groovy)
at sun.reflect.GeneratedMethodAccessor22.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:101)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:323)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1217)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuperN(ScriptBytecodeAdapter.java:144)
at org.apache.tinkerpop.gremlin.console.GremlinGroovysh.execute(GremlinGroovysh.groovy:83)
at org.codehaus.groovy.tools.shell.Shell.leftShift(Shell.groovy:120)
at org.codehaus.groovy.tools.shell.Shell$leftShift$1.call(Unknown Source)
at org.codehaus.groovy.tools.shell.ShellRunner.work(ShellRunner.groovy:93)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.super$2$work(InteractiveShellRunner.groovy)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:101)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:323)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1217)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuperN(ScriptBytecodeAdapter.java:144)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuper0(ScriptBytecodeAdapter.java:164)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.work(InteractiveShellRunner.groovy:138)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.runtime.callsite.PlainObjectMetaMethodSite.doInvoke(PlainObjectMetaMethodSite.java:43)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite$PogoCachedMethodSiteNoUnwrapNoCoerce.invoke(PogoMetaMethodSite.java:190)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:58)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:160)
at org.codehaus.groovy.tools.shell.ShellRunner.run(ShellRunner.groovy:57)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.super$2$run(InteractiveShellRunner.groovy)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:101)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:323)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1217)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuperN(ScriptBytecodeAdapter.java:144)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuper0(ScriptBytecodeAdapter.java:164)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.run(InteractiveShellRunner.groovy:97)
at org.codehaus.groovy.vmplugin.v7.IndyInterface.selectMethod(IndyInterface.java:234)
at org.apache.tinkerpop.gremlin.console.Console.(Console.groovy:168)
at org.codehaus.groovy.vmplugin.v7.IndyInterface.selectMethod(IndyInterface.java:234)
at org.apache.tinkerpop.gremlin.console.Console.main(Console.groovy:502)
Caused by: java.util.concurrent.ExecutionException: java.lang.UnsupportedOperationException: getRegionMetrics
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:192)
at org.apache.tinkerpop.gremlin.process.computer.traversal.step.map.VertexProgramStep.processNextStart(VertexProgramStep.java:68)
... 75 more
Caused by: java.lang.UnsupportedOperationException: getRegionMetrics
at com.google.cloud.bigtable.hbase2_x.BigtableAdmin.getRegionMetrics(BigtableAdmin.java:797)
at org.apache.hadoop.hbase.mapreduce.RegionSizeCalculator.init(RegionSizeCalculator.java:82)
at org.apache.hadoop.hbase.mapreduce.RegionSizeCalculator.(RegionSizeCalculator.java:61)
at org.apache.hadoop.hbase.mapreduce.TableInputFormatBase.createRegionSizeCalculator(TableInputFormatBase.java:593)
at org.apache.hadoop.hbase.mapreduce.TableInputFormatBase.oneInputSplitPerRegion(TableInputFormatBase.java:294)
at org.apache.hadoop.hbase.mapreduce.TableInputFormatBase.getSplits(TableInputFormatBase.java:257)
at org.apache.hadoop.hbase.mapreduce.TableInputFormat.getSplits(TableInputFormat.java:254)
at org.janusgraph.hadoop.formats.hbase.HBaseBinaryInputFormat.getSplits(HBaseBinaryInputFormat.java:57)
at org.janusgraph.hadoop.formats.util.HadoopInputFormat.getSplits(HadoopInputFormat.java:51)
at org.apache.spark.rdd.NewHadoopRDD.getPartitions(NewHadoopRDD.scala:130)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:253)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:251)
at scala.Option.getOrElse(Option.scala:121)
at org.apache.spark.rdd.RDD.partitions(RDD.scala:251)
at org.apache.spark.rdd.MapPartitionsRDD.getPartitions(MapPartitionsRDD.scala:49)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:253)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:251)
at scala.Option.getOrElse(Option.scala:121)
at org.apache.spark.rdd.RDD.partitions(RDD.scala:251)
at org.apache.spark.rdd.MapPartitionsRDD.getPartitions(MapPartitionsRDD.scala:49)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:253)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:251)
at scala.Option.getOrElse(Option.scala:121)
at org.apache.spark.rdd.RDD.partitions(RDD.scala:251)
at org.apache.spark.rdd.MapPartitionsRDD.getPartitions(MapPartitionsRDD.scala:49)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:253)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:251)
at scala.Option.getOrElse(Option.scala:121)
at org.apache.spark.rdd.RDD.partitions(RDD.scala:251)
at org.apache.spark.rdd.MapPartitionsRDD.getPartitions(MapPartitionsRDD.scala:49)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:253)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:251)
at scala.Option.getOrElse(Option.scala:121)
at org.apache.spark.rdd.RDD.partitions(RDD.scala:251)
at org.apache.spark.rdd.MapPartitionsRDD.getPartitions(MapPartitionsRDD.scala:49)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:253)
at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:251)
at scala.Option.getOrElse(Option.scala:121)
at org.apache.spark.rdd.RDD.partitions(RDD.scala:251)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2158)
at org.apache.spark.rdd.RDD$$anonfun$fold$1.apply(RDD.scala:1098)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
at org.apache.spark.rdd.RDD.withScope(RDD.scala:363)
at org.apache.spark.rdd.RDD.fold(RDD.scala:1092)
at org.apache.spark.api.java.JavaRDDLike$class.fold(JavaRDDLike.scala:414)
at org.apache.spark.api.java.AbstractJavaRDDLike.fold(JavaRDDLike.scala:45)
at org.apache.tinkerpop.gremlin.spark.process.computer.traversal.strategy.optimization.interceptor.SparkStarBarrierInterceptor.apply(SparkStarBarrierInterceptor.java:101)
at org.apache.tinkerpop.gremlin.spark.process.computer.traversal.strategy.optimization.interceptor.SparkStarBarrierInterceptor.apply(SparkStarBarrierInterceptor.java:66)
at org.apache.tinkerpop.gremlin.spark.process.computer.SparkGraphComputer.lambda$submitWithExecutor$1(SparkGraphComputer.java:380)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
```

Start by reproducing the OLAP count with the provided read-hbase-spark-yarn.properties configuration and inspect the HBaseBinaryInputFormat, HadoopInputFormat, and Spark NewHadoopRDD path. Trace the getRegionMetrics failure from BigtableAdmin through RegionSizeCalculator, and consider the issue complete when the same OLAP traversal runs successfully against Google Cloud BigTable.

Written by the indexing model from the issue text.