I am using EMR step functions to analyze data.
I wanted to store the count of the analyzed dataframe to decide whether I can save it as a csv or parquet. I would prefer CSV but if the size is too big, I wont be able to download it and use it on my laptop.
I used the count() method to store it to a int variable limit
When i try using the following code:
coalesce(1).write.format("text").option("header", "false").mode("overwrite").save("output.txt")
It says that:
int doesnt have any attribute called write
Is there a way to write integers or string to a file so that I can open it in my s3 bucket and inspect after the EMR step has run?
Update:
I tried the dataframe method as suggested by #Shu, but am getting the following error.
Caused by: org.apache.spark.SparkException: Job aborted due to stage
failure: Task 0 in stage 13.0 failed 4 times, most recent failure:
Lost task 0.3 in stage 13.0 (TID 19396, ip-10-210-13-34.ec2.internal,
executor 11): org.apache.spark.SparkException: Task failed while
writing rows. at
org.apache.spark.sql.execution.datasources.FileFormatWriter$.org$apache$spark$sql$execution$datasources$FileFormatWriter$$executeTask(FileFormatWriter.scala:257)
at
org.apache.spark.sql.execution.datasources.FileFormatWriter$$anonfun$write$1.apply(FileFormatWriter.scala:170)
What could be the root cause of this?
You can parallelize the int variable to create an rdd then write to HDFS using .saveAsTextFile
df.show()
#+---+
#| _1|
#+---+
#| a|
#| b|
#+---+
limit=df.count()
spark.sparkContext.parallelize([limit]).coalesce(1).saveAsTextFile("<path>")
#content of file
#cat <path>/part-00000
#2
Other way would be creating dataframe from count variable then write in csv format as header false.
from pyspark.sql.types import *
spark.createDataFrame(spark.sparkContext.parallelize([limit]),IntegerType()).coalesce(1).write.format("csv").option("header", "false").mode("overwrite").save("<path>")
#or in text format
spark.createDataFrame(spark.sparkContext.parallelize([limit]),StringType()).coalesce(1).write.format("text").mode("overwrite").save("<path>")
#cat part-*
#2
Related
My homework is giving me a hard time with pyspark. I have this view of my "df2" after a groupBy:
df2.groupBy('years').count().show()
+-----+-----+
|years|count|
+-----+-----+
| 2003|11904|
| 2006| 3476|
| 1997| 3979|
| 2004|13362|
| 1996| 3180|
| 1998| 4969|
| 1995| 1995|
| 2001|11532|
| 2005|11389|
| 2000| 7462|
| 1999| 6593|
| 2002|11799|
+-----+-----+
Every attempt to save this (and then load with pandas) to a file gives back the original source data text file form I read with pypspark with its original columns and attributes, only now its .csv but that's not the point.
What can I do to overcome this ?
For your concern I do not use SparkContext function in the begining of the code, just plain "read" and "groupBy".
df2.groupBy('years').count().write.csv("sample.csv")
or
df3=df2.groupBy('years').count()
df3.write.csv("sample.csv")
both of them will create sample.csv in your working directory
You can assign the results into a new dataframe results, and then write the results to a csv file. Note that there are two ways to output the csv. If you use spark you need to use .coalesce(1) to make sure only one file is outputted. The other way is to convert .toPandas() and use to_csv() function of pandas DataFrame.
results = df2.groupBy('years').count()
# writes a csv file "part-xxx.csv" inside a folder "results"
results.coalesce(1).write.csv("results", header=True)
# or if you want a csv file, not a csv file inside a folder (default behaviour of spark)
results.toPandas().to_csv("results.csv")
I have a series of files that are in JSON that need to be split into multiple files to reduce their size. One issue is that the files are extracted using a third party tool and arrive as a JSON object on a single line.
I can use S3 select to process a small file (say around 300Mb uncompressed) but when I try and use a larger file - say 1Gb uncompressed (90Mb gzip compressed) I get the following error:
[ERROR] EventStreamError: An error occurred (InternalError) when calling the SelectObjectContent operation: We encountered an internal error. Please try again.
The query that I am trying to run is:
select count(*) as rowcount from s3object[*][*] s
I can't run the query from the console because the file is larger than 128Mb but the code that is performing the operation is as follows:
def execute_select_query(bucket, key, query):
"""
Runs a query against an object in S3.
"""
if key.endswith("gz"):
compression = "GZIP"
else:
compression = "NONE"
LOGGER.info("Running query |%s| against s3://%s/%s", query, bucket, key)
return S3_CLIENT.select_object_content(
Bucket=bucket,
Key=key,
ExpressionType='SQL',
Expression=query,
InputSerialization={"JSON": {"Type": "DOCUMENT"}, "CompressionType": compression},
OutputSerialization={'JSON': {}},
)
I have set up a spark cluster with a master and 2 slaves (I'm using Spark Standalone). The cluster is working well with some of the examples but not my application. My application workflow is that, it will read the csv -> extract each line in the csv along with the header -> convert to JSON -> save to S3. Here is my code:
def upload_func(row):
f = row.toJSON()
f.saveAsTextFile("s3n://spark_data/"+ row.name +".json")
print(f)
print(row.name)
if __name__ == "__main__":
spark = SparkSession \
.builder \
.appName("Python Spark SQL data source example") \
.getOrCreate()
df = spark.read.csv("sample.csv", header=True, mode="DROPMALFORMED")
df.rdd.map(upload_func)
I have also export the AWS_Key_ID and AWS_Secret_Key into the ec2 environment. However with the above code, my application does not work. Below are the issues:
The JSON files are not saved in S3, I have tried run the application few times and also reload the S3 page but no data. The application completed without any error in the log. Also, the print(f) and print(row.name) are not printed out in the log. What do I need to fix to get the JSON save on S3 and is there anyway for me to print on the log for debug purpose?
Currently I need to put the csv file in the worker node so the application can read the csv file. How can I put the file in another place, let say the master node and when the application runs, it will split the csv file to all the worker nodes so they can do the upload parallel as a distributed system?
Help is really appreciated. Thanks for your help in advance.
UPDATED
After putting Logger to debug, I have identified the issue that the map function upload_func() is not being called or the application could not get inside this function (Logger printed messages before and after function call). Please help if you know the reason why?
you need to force the map to be evaluated; spark will only execute work on demand.
df.rdd.map(upload_func).count() should do it
I am trying to trigger hive on spark using hue interface . The job works perfectly when run from commandline but when i try to run from hue it throws exceptions. In hue, I tried mainly two things:
1) when I give all the properties in .hql file using set commands
set spark.home=/usr/lib/spark;
set hive.execution.engine=spark;
set spark.eventLog.enabled=true;
add jar /usr/lib/spark/assembly/lib/spark-assembly-1.5.0-cdh5.5.1-hadoop2.6.0-cdh5.5.1.jar;
set spark.eventLog.dir=hdfs://10.11.50.81:8020/tmp/;
set spark.executor.memory=2899102923;
I get an error
ERROR : Failed to execute spark task, with exception 'org.apache.hadoop.hive.ql.metadata.HiveException(Unsupported execution engine: Spark. Please set hive.execution.engine=mr)'
org.apache.hadoop.hive.ql.metadata.HiveException: Unsupported execution engine: Spark. Please set hive.execution.engine=mr
2) when I give properties in hue properties, it just works with mr engine but not spark execution engine.
Any help would be appreciated
I have solved this issue by using a shell action in oozie.
This shell action invokes a pyspark action bearing my sql file.
Even though the job shows as MR in jobtracker, spark history server recognizes as a spark action and the output is achieved.
shell file:
#!/bin/bash
export PYTHONPATH=`pwd`
spark-submit --master local testabc.py
python file:
from pyspark.sql import HiveContext
from pyspark import SparkContext
sc = SparkContext();
sqlContext = HiveContext(sc)
result = sqlContext.sql("insert into table testing_oozie.table2 select * from testing_oozie.table1 ");
result.show()
I'm not getting the Google example work
https://cloud.google.com/hadoop/examples/bigquery-connector-spark-example
PySpark
There are a few mistakes in the code i think, like:
'# Output Parameters
'mapred.bq.project.id': '',
Should be: 'mapred.bq.output.project.id': '',
and
'# Write data back into new BigQuery table.
'# BigQueryOutputFormat discards keys, so set key to None.
(word_counts
.map(lambda pair: None, json.dumps(pair))
.saveAsNewAPIHadoopDataset(conf))
will give an error message. If I change it to:
(word_counts
.map(lambda pair: (None, json.dumps(pair)))
.saveAsNewAPIHadoopDataset(conf))
I get the error message:
org.apache.hadoop.io.Text cannot be cast to com.google.gson.JsonObject
And whatever I try I can not make this work.
There is a dataset created in BigQuery with the name I gave it in the 'conf' with a trailing '_hadoop_temporary_job_201512081419_0008'
And a table is created with '_attempt_201512081419_0008_r_000000_0' on the end. But are always empty
Can anybody help me with this?
Thanks
We are working to update the documentation because, as you noted, the docs are incorrect in this case. Sorry about that! While we're working to update the docs, I wanted to get you a reply ASAP.
Casting problem
The most important problem you mention is the casting issue. Unfortunately,PySpark cannot use the BigQueryOutputFormat to create Java GSON objects. The solution (workaround) is to save the output data into Google Cloud Storage (GCS) and then load it manually with the bq command.
Code example
Here is a code sample which exports to GCS and loads the data into BigQuery. You could also use subprocess and Python to execute the bq command programatically.
#!/usr/bin/python
"""BigQuery I/O PySpark example."""
import json
import pprint
import pyspark
sc = pyspark.SparkContext()
# Use the Google Cloud Storage bucket for temporary BigQuery export data used
# by the InputFormat. This assumes the Google Cloud Storage connector for
# Hadoop is configured.
bucket = sc._jsc.hadoopConfiguration().get('fs.gs.system.bucket')
project = sc._jsc.hadoopConfiguration().get('fs.gs.project.id')
input_directory ='gs://{}/hadoop/tmp/bigquery/pyspark_input'.format(bucket)
conf = {
# Input Parameters
'mapred.bq.project.id': project,
'mapred.bq.gcs.bucket': bucket,
'mapred.bq.temp.gcs.path': input_directory,
'mapred.bq.input.project.id': 'publicdata',
'mapred.bq.input.dataset.id': 'samples',
'mapred.bq.input.table.id': 'shakespeare',
}
# Load data in from BigQuery.
table_data = sc.newAPIHadoopRDD(
'com.google.cloud.hadoop.io.bigquery.JsonTextBigQueryInputFormat',
'org.apache.hadoop.io.LongWritable',
'com.google.gson.JsonObject',
conf=conf)
# Perform word count.
word_counts = (
table_data
.map(lambda (_, record): json.loads(record))
.map(lambda x: (x['word'].lower(), int(x['word_count'])))
.reduceByKey(lambda x, y: x + y))
# Display 10 results.
pprint.pprint(word_counts.take(10))
# Stage data formatted as newline delimited json in Google Cloud Storage.
output_directory = 'gs://{}/hadoop/tmp/bigquery/pyspark_output'.format(bucket)
partitions = range(word_counts.getNumPartitions())
output_files = [output_directory + '/part-{:05}'.format(i) for i in partitions]
(word_counts
.map(lambda (w, c): json.dumps({'word': w, 'word_count': c}))
.saveAsTextFile(output_directory))
# Manually clean up the input_directory, otherwise there will be BigQuery export
# files left over indefinitely.
input_path = sc._jvm.org.apache.hadoop.fs.Path(input_directory)
input_path.getFileSystem(sc._jsc.hadoopConfiguration()).delete(input_path, True)
print """
###########################################################################
# Finish uploading data to BigQuery using a client e.g.
bq load --source_format NEWLINE_DELIMITED_JSON \
--schema 'word:STRING,word_count:INTEGER' \
wordcount_dataset.wordcount_table {files}
# Clean up the output
gsutil -m rm -r {output_directory}
###########################################################################
""".format(
files=','.join(output_files),
output_directory=output_directory)