Finding the Max value in JavaPairDStream - hadoop

Is there a way to find the max from a JavaPairDStream? My key is a String and value is ArrayList<Row>. I need to find a tuple which has the max value of a certain column of the row in the ArrayList . I am using spark 1.6
I want to implement something similar to javaRDD.max() for a JavaPairDstream.
Using updateStateByKey is not an option as i need the associative state for all the keys and not per key .
I have tried using accumulators in the following the way :
**
if(accumulator.value()< max)
{
accumulator.setValue(max);
}
**
i do this inside reduceByKey , but i get the following exception :
org.apache.spark.SparkException: Job aborted due to stage failure: Task 0 in stage 0.0 failed 1 times, most recent failure: Lost task 0.0 in stage 0.0 (TID 0, localhost): java.lang.UnsupportedOperationException: Can't read accumulator value in task
at org.apache.spark.Accumulable.value(Accumulators.scala:98)
at sample.sample.SampleJdd$2.call(SampleJdd.java:82)
at sample.sample.SampleJdd$2.call(SampleJdd.java:74)
at org.apache.spark.api.java.JavaPairRDD$$anonfun$toScalaFunction2$1.apply(JavaPairRDD.scala:996)
at org.apache.spark.util.collection.ExternalSorter$$anonfun$5.apply(ExternalSorter.scala:200)
at org.apache.spark.util.collection.ExternalSorter$$anonfun$5.apply(ExternalSorter.scala:199)
at org.apache.spark.util.collection.AppendOnlyMap.changeValue(AppendOnlyMap.scala:138)
at org.apache.spark.util.collection.SizeTrackingAppendOnlyMap.changeValue(SizeTrackingAppendOnlyMap.scala:32)
at org.apache.spark.util.collection.ExternalSorter.insertAll(ExternalSorter.scala:205)
at org.apache.spark.shuffle.sort.SortShuffleWriter.write(SortShuffleWriter.scala:56)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:68)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:41)
at org.apache.spark.scheduler.Task.run(Task.scala:64)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:203)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Driver stacktrace:
at org.apache.spark.scheduler.DAGScheduler.org$apache$spark$scheduler$DAGScheduler$$failJobAndIndependentStages(DAGScheduler.scala:1204)
at org.apache.spark.scheduler.DAGScheduler$$anonfun$abortStage$1.apply(DAGScheduler.scala:1193)
at org.apache.spark.scheduler.DAGScheduler$$anonfun$abortStage$1.apply(DAGScheduler.scala:1192)
at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:47)
at org.apache.spark.scheduler.DAGScheduler.abortStage(DAGScheduler.scala:1192)
at org.apache.spark.scheduler.DAGScheduler$$anonfun$handleTaskSetFailed$1.apply(DAGScheduler.scala:693)
at org.apache.spark.scheduler.DAGScheduler$$anonfun$handleTaskSetFailed$1.apply(DAGScheduler.scala:693)
at scala.Option.foreach(Option.scala:236)
at org.apache.spark.scheduler.DAGScheduler.handleTaskSetFailed(DAGScheduler.scala:693)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:1393)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:1354)
org.apache.spark.util.EventLoop$$anon$1.run(EventLoop.scala:48

Related

Hadoop Spark SQL insert failing

I'm trying to insert something around 13M rows into a new table but I'm getting the following error:
22/12/09 19:33:56 ERROR Utils: Aborting task
java.lang.AssertionError: assertion failed: Created file counter 11 is beyond max value 10
at scala.Predef$.assert(Predef.scala:223)
at org.apache.spark.sql.execution.datasources.DynamicPartitionDataWriter.$anonfun$increaseCreatedFileAndCheck$1(FileFormatDataWriter.scala:191)
at scala.runtime.java8.JFunction1$mcVI$sp.apply(JFunction1$mcVI$sp.java:23)
at scala.Option.foreach(Option.scala:407)
at org.apache.spark.sql.execution.datasources.DynamicPartitionDataWriter.increaseCreatedFileAndCheck(FileFormatDataWriter.scala:188)
at org.apache.spark.sql.execution.datasources.DynamicPartitionDataWriter.write(FileFormatDataWriter.scala:277)
at org.apache.spark.sql.execution.datasources.FileFormatWriter$.$anonfun$executeTask$1(FileFormatWriter.scala:280)
at org.apache.spark.util.Utils$.tryWithSafeFinallyAndFailureCallbacks(Utils.scala:1473)
at org.apache.spark.sql.execution.datasources.FileFormatWriter$.executeTask(FileFormatWriter.scala:288)
at org.apache.spark.sql.execution.datasources.FileFormatWriter$.$anonfun$write$15(FileFormatWriter.scala:211)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:90)
at org.apache.spark.scheduler.Task.run(Task.scala:131)
at org.apache.spark.executor.Executor$TaskRunner.$anonfun$run$3(Executor.scala:498)
at org.apache.spark.util.Utils$.tryWithSafeFinally(Utils.scala:1439)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:501)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
22/12/09 19:33:57 ERROR FileFormatWriter: Job job_202212091917352650741377131539872_0020 aborted.
22/12/09 19:33:57 ERROR Executor: Exception in task 0.1 in stage 20.0 (TID 26337)
org.apache.spark.SparkException: Task failed while writing rows.
at org.apache.spark.sql.execution.datasources.FileFormatWriter$.executeTask(FileFormatWriter.scala:298)
at org.apache.spark.sql.execution.datasources.FileFormatWriter$.$anonfun$write$15(FileFormatWriter.scala:211)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:90)
at org.apache.spark.scheduler.Task.run(Task.scala:131)
at org.apache.spark.executor.Executor$TaskRunner.$anonfun$run$3(Executor.scala:498)
at org.apache.spark.util.Utils$.tryWithSafeFinally(Utils.scala:1439)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:501)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.AssertionError: assertion failed: Created file counter 11 is beyond max value 10
at scala.Predef$.assert(Predef.scala:223)
at org.apache.spark.sql.execution.datasources.DynamicPartitionDataWriter.$anonfun$increaseCreatedFileAndCheck$1(FileFormatDataWriter.scala:191)
at scala.runtime.java8.JFunction1$mcVI$sp.apply(JFunction1$mcVI$sp.java:23)
at scala.Option.foreach(Option.scala:407)
at org.apache.spark.sql.execution.datasources.DynamicPartitionDataWriter.increaseCreatedFileAndCheck(FileFormatDataWriter.scala:188)
at org.apache.spark.sql.execution.datasources.DynamicPartitionDataWriter.write(FileFormatDataWriter.scala:277)
at org.apache.spark.sql.execution.datasources.FileFormatWriter$.$anonfun$executeTask$1(FileFormatWriter.scala:280)
at org.apache.spark.util.Utils$.tryWithSafeFinallyAndFailureCallbacks(Utils.scala:1473)
at org.apache.spark.sql.execution.datasources.FileFormatWriter$.executeTask(FileFormatWriter.scala:288)
The insert operation is like the following:
insert overwrite table fake_table_txt partition(partition_name)
select id, name, type, description from ( inner query )
I'm a Hadoop beginner and I have no idea what may be causing this.
Could anybody please give me any direction?
After struggling a little, I was told that increasing the property "files per task" would do the trick.
set spark.sql.maxCreatedFilesPerTask = 15;
It was defaulted to 10 previously.

Pyspark streaming write in elasticsearch

Is there a way to write through Spark Streaming, reading from kafka and write in ElasticSearch?
I tried something like... As explained in the ElasticSearch docs (with very little documentation regarding pyspark):
sc = SparkContext("local[2]", appName="TwitterStreamKafka")
ssc = StreamingContext(sc, batchIntervalSeconds)
topic = url_topic
tweets = KafkaUtils.createStream(ssc, zkQuorum, "spark-streaming-consumer", {topic: 1})
tweets.pprint()
conf = {"es.resource": "credentials/credential"} # assume Elasticsearch is running on localhost defaults
if tweets.count() > 0:
tweets.foreachRDD(lambda rdd: rdd.saveAsNewAPIHadoopFile(
path='-',
outputFormatClass="org.elasticsearch.hadoop.mr.EsOutputFormat",
keyClass="org.apache.hadoop.io.NullWritable",
valueClass="org.elasticsearch.hadoop.mr.LinkedMapWritable",
conf=conf))
ssc.start()
ssc.awaitTermination()
But it doesn't work. The error is:
17/11/10 17:16:35 ERROR Utils: Aborting task
org.elasticsearch.hadoop.rest.EsHadoopInvalidRequest: Found unrecoverable error [127.0.0.1:9200] returned Bad Request(400) - failed to parse; Bailing out..
at org.elasticsearch.hadoop.rest.RestClient.processBulkResponse(RestClient.java:251)
at org.elasticsearch.hadoop.rest.RestClient.bulk(RestClient.java:203)
at org.elasticsearch.hadoop.rest.RestRepository.tryFlush(RestRepository.java:222)
at org.elasticsearch.hadoop.rest.RestRepository.flush(RestRepository.java:244)
at org.elasticsearch.hadoop.rest.RestRepository.close(RestRepository.java:269)
at org.elasticsearch.hadoop.mr.EsOutputFormat$EsRecordWriter.doClose(EsOutputFormat.java:214)
at org.elasticsearch.hadoop.mr.EsOutputFormat$EsRecordWriter.close(EsOutputFormat.java:196)
at org.apache.spark.internal.io.SparkHadoopMapReduceWriter$$anonfun$4.apply(SparkHadoopMapReduceWriter.scala:155)
at org.apache.spark.internal.io.SparkHadoopMapReduceWriter$$anonfun$4.apply(SparkHadoopMapReduceWriter.scala:144)
at org.apache.spark.util.Utils$.tryWithSafeFinallyAndFailureCallbacks(Utils.scala:1375)
at org.apache.spark.internal.io.SparkHadoopMapReduceWriter$.org$apache$spark$internal$io$SparkHadoopMapReduceWriter$$executeTask(SparkHadoopMapReduceWriter.scala:159)
at org.apache.spark.internal.io.SparkHadoopMapReduceWriter$$anonfun$3.apply(SparkHadoopMapReduceWriter.scala:89)
at org.apache.spark.internal.io.SparkHadoopMapReduceWriter$$anonfun$3.apply(SparkHadoopMapReduceWriter.scala:88)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87)
at org.apache.spark.scheduler.Task.run(Task.scala:108)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:335)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
17/11/10 17:16:35 ERROR SparkHadoopMapReduceWriter: Task attempt_20171110171633_0003_r_000000_0 aborted.
17/11/10 17:16:35 ERROR Executor: Exception in task 0.0 in stage 3.0 (TID 3)
org.apache.spark.SparkException: Task failed while writing rows
at org.apache.spark.internal.io.SparkHadoopMapReduceWriter$.org$apache$spark$internal$io$SparkHadoopMapReduceWriter$$executeTask(SparkHadoopMapReduceWriter.scala:178)
at org.apache.spark.internal.io.SparkHadoopMapReduceWriter$$anonfun$3.apply(SparkHadoopMapReduceWriter.scala:89)
at org.apache.spark.internal.io.SparkHadoopMapReduceWriter$$anonfun$3.apply(SparkHadoopMapReduceWriter.scala:88)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87)
at org.apache.spark.scheduler.Task.run(Task.scala:108)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:335)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
This is the command I use to execute it:
spark-submit --jars elasticsearch-hadoop-5.6.4.jar,spark-streaming-kafka-0-10-assembly_2.11-2.2.0.jar es_spark_write.py
I am using spark 2.2.0
The messages from Kafka are key-message json like these:
(u'urls', u'{"token": "secret_token", "count": 2443}')

Groovy Script Execution Exception

Can anyone tell me what approach I need to take to solve the below exception?
[2017-05-23 15:28:48,783][DEBUG][action.search.type ] [Mister Buda] [2217] Failed to execute fetch phase
org.elasticsearch.script.groovy.GroovyScriptExecutionException: NullPointerException[null]
at org.elasticsearch.script.groovy.GroovyScriptEngineService$GroovyScript.run(GroovyScriptEngineService.java:274)
at org.elasticsearch.search.fetch.script.ScriptFieldsFetchSubPhase.hitExecute(ScriptFieldsFetchSubPhase.java:74)
at org.elasticsearch.search.fetch.FetchPhase.execute(FetchPhase.java:194)
at org.elasticsearch.search.SearchService.executeFetchPhase(SearchService.java:516)
at org.elasticsearch.search.action.SearchServiceTransportAction$17.call(SearchServiceTransportAction.java:452)
at org.elasticsearch.search.action.SearchServiceTransportAction$17.call(SearchServiceTransportAction.java:449)
at org.elasticsearch.search.action.SearchServiceTransportAction$23.run(SearchServiceTransportAction.java:559)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
I see this exception during querying an index, that query contains a script_field.
I am using elasticsearch version 1.5.
This is the script,
(( _source.rating.'${amount}'.costRating.value * costWeighting) + ( _source.rating.flexibilityRating.value * (1 - costWeighting))) * 10
Here's the image of the sample data in the index,

slave lost and very slow join in spark

I did a join of two dataframes on one common column and then ran a show method:
df= df1.join(df2, df1.col1== df2.col2, 'inner')
df.show()
Then join ran very slow and finally raise an error: slave lost.
Py4JJavaError: An error occurred while calling o109.showString.
: org.apache.spark.SparkException: Job aborted due to stage failure: Task 0 in stage 8.0 failed 4 times, most recent failure: Lost task 0.3 in stage 8.0 : ExecutorLostFailure (executor 1 exited caused by one of the running tasks) Reason: Slave lost
Driver stacktrace:
at
org.apache.spark.scheduler.DAGScheduler.org$apache$spark$scheduler$DAGScheduler$$failJobAndIndependentStages(DAGScheduler.scala:1431)
at
org.apache.spark.scheduler.DAGScheduler$$anonfun$abortStage$1.apply(DAGScheduler.scala:1419)
at
org.apache.spark.scheduler.DAGScheduler$$anonfun$abortStage$1.apply(DAGScheduler.scala:1418)
at
scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:47)
at
org.apache.spark.scheduler.DAGScheduler.abortStage(DAGScheduler.scala:1418)
at
org.apache.spark.scheduler.DAGScheduler$$anonfun$handleTaskSetFailed$1.apply(DAGScheduler.scala:799)
at
org.apache.spark.scheduler.DAGScheduler$$anonfun$handleTaskSetFailed$1.apply(DAGScheduler.scala:799)
at scala.Option.foreach(Option.scala:236) at
org.apache.spark.scheduler.DAGScheduler.handleTaskSetFailed(DAGScheduler.scala:799)
at
org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.doOnReceive(DAGScheduler.scala:1640)
at
org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:1599)
at
org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:1588)
at org.apache.spark.util.EventLoop$$anon$1.run(EventLoop.scala:48)
at
org.apache.spark.scheduler.DAGScheduler.runJob(DAGScheduler.scala:620)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:1832) at
org.apache.spark.SparkContext.runJob(SparkContext.scala:1845) at
org.apache.spark.SparkContext.runJob(SparkContext.scala:1858) at
org.apache.spark.sql.execution.SparkPlan.executeTake(SparkPlan.scala:212)
at
org.apache.spark.sql.execution.Limit.executeCollect(basicOperators.scala:165)
at
org.apache.spark.sql.execution.SparkPlan.executeCollectPublic(SparkPlan.scala:174)
at
org.apache.spark.sql.DataFrame$$anonfun$org$apache$spark$sql$DataFrame$$execute$1$1.apply(DataFrame.scala:1499)
at
org.apache.spark.sql.DataFrame$$anonfun$org$apache$spark$sql$DataFrame$$execute$1$1.apply(DataFrame.scala:1499)
at
org.apache.spark.sql.execution.SQLExecution$.withNewExecutionId(SQLExecution.scala:56)
at
org.apache.spark.sql.DataFrame.withNewExecutionId(DataFrame.scala:2086)
at
org.apache.spark.sql.DataFrame.org$apache$spark$sql$DataFrame$$execute$1(DataFrame.scala:1498)
at
org.apache.spark.sql.DataFrame.org$apache$spark$sql$DataFrame$$collect(DataFrame.scala:1505)
at
org.apache.spark.sql.DataFrame$$anonfun$head$1.apply(DataFrame.scala:1375)
at
org.apache.spark.sql.DataFrame$$anonfun$head$1.apply(DataFrame.scala:1374)
at org.apache.spark.sql.DataFrame.withCallback(DataFrame.scala:2099)
at org.apache.spark.sql.DataFrame.head(DataFrame.scala:1374) at
org.apache.spark.sql.DataFrame.take(DataFrame.scala:1456) at
org.apache.spark.sql.DataFrame.showString(DataFrame.scala:170) at
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498) at
py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:231) at
py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:381) at
py4j.Gateway.invoke(Gateway.java:259) at
py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:133)
at py4j.commands.CallCommand.execute(CallCommand.java:79) at
py4j.GatewayConnection.run(GatewayConnection.java:209) at
java.lang.Thread.run(Thread.java:745)
After some search, it seems this is a memory related issue. Then I increased repartition to 3000, increased executor memory,increased memoryOverhead, but still no luck, I got the same slave lost error. During df.show(), I found one of the execuctor shuffle write size is very high, the others were not so high.
Any clue?
Thanks
If using scala try
val df = df1.join(df2,Seq("column name"))
if pyspark
df = df1.join(df2,["columnname"])
or
df = df1.join(df2,df1.columnname == df2.columnname)
display(df)
If trying to do same in pyspark - sql
df1.createOrReplaceTempView("left_test_table")
df2..createOrReplaceTempView("right_test_table")
left <- sql(sqlContext, "SELECT * FROM left_test_table")
right <- sql(sqlContext, "SELECT * FROM right_test_table")
head(drop(join(left, right), left$name))

Implementing OLAP on titan/cassandra graph

I am using Titan 1.0.0 on top cassandra. I want to use OLAP services using SparkGraphComputer on the titan/cassandra graph. I have two questions
1) How to do it?
config:
https://github.com/thinkaurelius/titan/blob/titan10/titan-dist/src/assembly/static/conf/hadoop-graph/read-cassandra.properties
gremlin-code:
graph = GraphFactory.open('conf/hadoop-graph/read-cassandra.properties')
g = graph.traversal(computer(SparkGraphComputer))
g.V().count() //Here is the error
Error:
11:20:33 ERROR org.apache.spark.executor.Executor - Exception in task 3.0 in stage 0.0 (TID 3)
java.lang.RuntimeException: error communicating via Thrift
at org.apache.cassandra.hadoop.ColumnFamilyRecordReader$RowIterator.<init>(ColumnFamilyRecordReader.java:267)
at org.apache.cassandra.hadoop.ColumnFamilyRecordReader$RowIterator.<init>(ColumnFamilyRecordReader.java:215)
at org.apache.cassandra.hadoop.ColumnFamilyRecordReader$StaticRowIterator.<init>(ColumnFamilyRecordReader.java:331)
at org.apache.cassandra.hadoop.ColumnFamilyRecordReader$StaticRowIterator.<init>(ColumnFamilyRecordReader.java:331)
at org.apache.cassandra.hadoop.ColumnFamilyRecordReader.initialize(ColumnFamilyRecordReader.java:171)
at com.thinkaurelius.titan.hadoop.formats.cassandra.CassandraBinaryRecordReader.initialize(CassandraBinaryRecordReader.java:39)
at com.thinkaurelius.titan.hadoop.formats.util.GiraphRecordReader.initialize(GiraphRecordReader.java:38)
at org.apache.spark.rdd.NewHadoopRDD$$anon$1.<init>(NewHadoopRDD.scala:135)
at org.apache.spark.rdd.NewHadoopRDD.compute(NewHadoopRDD.scala:107)
at org.apache.spark.rdd.NewHadoopRDD.compute(NewHadoopRDD.scala:69)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:280)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:247)
at org.apache.spark.rdd.MappedRDD.compute(MappedRDD.scala:31)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:280)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:247)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:68)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:41)
at org.apache.spark.scheduler.Task.run(Task.scala:56)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:200)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Here is the full trace :
http://pastebin.com/CiuXjFB2
2) Why convert to hadoopGraph when the data is already stored on titan/cassandra?
references:
https://groups.google.com/forum/#!topic/gremlin-users/fVijONCxvSI

Resources