Search code examples
importapache-sparkpysparkgoogle-cloud-dataproc

use an external library in pyspark job in a Spark cluster from google-dataproc

I have a spark cluster I created via google dataproc. I want to be able to use the csv library from databricks (see https://github.com/databricks/spark-csv). So I first tested it like this:

I started a ssh session with the master node of my cluster, then I input:

pyspark --packages com.databricks:spark-csv_2.11:1.2.0

Then it launched a pyspark shell in which I input:

df = sqlContext.read.format('com.databricks.spark.csv').options(header='true', inferschema='true').load('gs:/xxxx/foo.csv')
df.show()

And it worked.

My next step is to launch this job from my main machine using the command:

gcloud beta dataproc jobs submit pyspark --cluster <my-dataproc-cluster> my_job.py

But here It does not work and I get an error. I think because I did not gave the --packages com.databricks:spark-csv_2.11:1.2.0 as an argument, but I tried 10 different ways to give it and I did not manage.

My question are:

  1. was the databricks csv library installed after I typed pyspark --packages com.databricks:spark-csv_2.11:1.2.0
  2. can I write a line in my job.py in order to import it?
  3. or what params should I give to my gcloud command to import it or install it?
Solution

  • Short Answer

    There are quirks in ordering of arguments where --packages isn't accepted by spark-submit if it comes after the my_job.py argument. To workaround this, you can do the following when submitting from Dataproc's CLI:

    gcloud beta dataproc jobs submit pyspark --cluster <my-dataproc-cluster> \
    --properties spark.jars.packages=com.databricks:spark-csv_2.11:1.2.0 my_job.py

    Basically, just add --properties spark.jars.packages=com.databricks:spark-csv_2.11:1.2.0 before the .py file in your command.

    Long Answer

    So, this is actually a different issue than the known lack of support for --jars in gcloud beta dataproc jobs submit pyspark; it appears that without Dataproc explicitly recognizing --packages as a special spark-submit-level flag, it tries to pass it after the application arguments so that spark-submit lets the --packages fall through as an application argument rather than properly parsing it as a submission-level option. Indeed, in an SSH session, the following does not work:

    # Doesn't work if job.py depends on that package.
spark-submit job.py --packages com.databricks:spark-csv_2.11:1.2.0

    But switching the order of the arguments does work again, even though in the pyspark case, both orderings work:

    # Works with dependencies on that package.
spark-submit --packages com.databricks:spark-csv_2.11:1.2.0 job.py
pyspark job.py --packages com.databricks:spark-csv_2.11:1.2.0
pyspark --packages com.databricks:spark-csv_2.11:1.2.0 job.py

    So even though spark-submit job.py is supposed to be a drop-in replacement for everything that previously called pyspark job.py, the difference in parse ordering for things like --packages means it's not actually a 100% compatible migration. This might be something to follow up with on the Spark side.

    Anyhow, fortunately there's a workaround, since --packages is just another alias for the Spark property spark.jars.packages, and Dataproc's CLI supports properties just fine. So you can just do the following:

    gcloud beta dataproc jobs submit pyspark --cluster <my-dataproc-cluster> \
    --properties spark.jars.packages=com.databricks:spark-csv_2.11:1.2.0 my_job.py

    Note that the --properties must come before the my_job.py, otherwise it gets sent as an application argument rather than as a configuration flag. Hope that works for you! Note that the equivalent in an SSH session would be spark-submit --packages com.databricks:spark-csv_2.11:1.2.0 job.py.