Sean Pecker
03/03/2024, 5:27 PMScout
03/03/2024, 5:27 PMspark-submit
. This approach is suitable for migrating existing Spark jobs and works for Spark jobs written in Java or Scala. However, it is less integrated with Dagster's features, and writing unit tests can be cumbersome. 2. Asset accepts and produces DataFrames or RDDs: With this approach, the asset definition consists of pure logical data transformations on Spark DataFrames or RDDs. The @asset
-decorated function accepts DataFrames
as parameters and returns DataFrames
upon completion. An IO manager handles writing and reading the DataFrames to and from persistent storage. If you want your Spark driver to run inside a Spark cluster, you use a "step launcher" resource that informs Dagster how to launch the step. This approach has a clean local testing story and allows you to run an entire pipeline of Spark assets in a single process. However, it only works with PySpark, and setting up a step launcher can be difficult. For a self-hosted Spark cluster in a Docker container, you would likely use the first approach, where the asset body submits the Spark job, possibly using spark-submit
to submit jobs to your cluster. This allows you to manage your Spark cluster independently of Dagster while still using Dagster to orchestrate the overall ETL pipeline. Remember that when integrating with Spark, you may need to consider networking, storage, and other infrastructure concerns to ensure that Dagster can communicate with the Spark cluster and that data can be persisted and accessed as needed.Sean Pecker
03/03/2024, 5:30 PMScout
03/03/2024, 5:30 PMdocker-compose.yml
, Dockerfile
, and asset body specifically for orchestrating a Spark ETL pipeline in a self-hosted Spark cluster within a Docker container. However, I can guide you through the general components you would need for each part based on the documentation's guidance on Docker and Kubernetes deployments, as well as general Docker and Spark practices.
### Dockerfile
Your Dockerfile
would need to include your Dagster project, the Dagster library, and any other dependencies required to submit jobs to your Spark cluster. Here's a simplified example:
Dockerfile
FROM python:3.8-slim
# Install Java, which is required for Spark
RUN apt-get update && \
apt-get install -y openjdk-11-jre-headless && \
apt-get clean;
# Set the working directory
WORKDIR /app
# Copy your Dagster project code into the container
COPY . /app
# Install Dagster and any other dependencies
RUN pip install dagster dagster-spark
# Your entrypoint here would be whatever is appropriate for your Dagster deployment
CMD ["dagit", "-h", "0.0.0.0", "-p", "3000"]
### docker-compose.yml
Your docker-compose.yml
would define services for Dagster and your Spark cluster. Here's a simplified example:
yaml
version: '3.7'
services:
dagster:
build: .
ports:
- "3000:3000"
environment:
- SPARK_MASTER_URL=<spark://spark-master:7077>
depends_on:
- spark-master
spark-master:
image: bitnami/spark:latest
environment:
- SPARK_MODE=master
ports:
- "8080:8080"
- "7077:7077"
spark-worker:
image: bitnami/spark:latest
environment:
- SPARK_MODE=worker
- SPARK_MASTER_URL=<spark://spark-master:7077>
depends_on:
- spark-master
### Asset Body
The asset body would use Python's subprocess module to call spark-submit
and submit a job to the Spark cluster. Here's a simplified example:
python
from dagster import asset
import subprocess
@asset
def my_spark_etl():
# Define the spark-submit command
submit_command = [
"spark-submit",
"--master", "<spark://spark-master:7077>",
"--class", "org.myorg.MySparkJob",
"/path/to/my/spark-job.jar"
]
# Run the spark-submit command
result = subprocess.run(submit_command, capture_output=True, text=True)
# Handle the result
if result.returncode != 0:
raise Exception(f"Spark job failed with the following output: {result.stderr}")
# Return some result or output path
return "path/to/output"
Please note that this is a very high-level example and does not include error handling, logging, or other best practices. You would need to adapt this to your specific Spark job, cluster configuration, andScout
03/03/2024, 5:31 PMSean Pecker
03/03/2024, 5:32 PMScout
03/03/2024, 5:32 PM.zip
or .egg
file and using the --py-files
argument with spark-submit
to distribute them to the Spark workers.
Here's how you might adjust the Dockerfile
, docker-compose.yml
, and asset body to handle a PySpark job with multiple Python file dependencies:
### Dockerfile
The Dockerfile
would remain largely the same, but you should ensure that all your Python files are copied into the Docker image:
Dockerfile
FROM python:3.8-slim
# Install Java, which is required for Spark
RUN apt-get update && \
apt-get install -y openjdk-11-jre-headless && \
apt-get clean;
# Set the working directory
WORKDIR /app
# Copy your Dagster project code and PySpark job files into the container
COPY . /app
# Install Dagster, Dagster-Spark, and any other dependencies
RUN pip install dagster dagster-spark pyspark
# Your entrypoint here would be whatever is appropriate for your Dagster deployment
CMD ["dagit", "-h", "0.0.0.0", "-p", "3000"]
### docker-compose.yml
The docker-compose.yml
file would not need significant changes from the previous example, as it's mainly concerned with service orchestration and networking.
### Asset Body
For the asset body, you would use the --py-files
argument to include your .zip
or .egg
file when submitting the job. Here's an example of how you might adjust the asset body:
python
from dagster import asset
import subprocess
@asset
def my_pyspark_etl():
# Path to your main PySpark script
main_script = "/path/to/my_main_pyspark_script.py"
# Path to the .zip file containing your Python dependencies
py_files = "/path/to/my_python_files.zip"
# Define the spark-submit command
submit_command = [
"spark-submit",
"--master", "<spark://spark-master:7077>",
"--py-files", py_files,
main_script
]
# Run the spark-submit command
result = subprocess.run(submit_command, capture_output=True, text=True)
# Handle the result
if result.returncode != 0:
raise Exception(f"Spark job failed with the following output: {result.stderr}")
# Return some result or output path
return "path/to/output"
In this example, my_python_files.zip
should contain all the Python files that your main PySpark script (my_main_pyspark_script.py
) depends on. You can create this .zip
file as part of your build process or within your Dockerfile.
Remember to adjust the paths to match where your files are located within the Docker container. Also, ensure that your Docker cScout
03/03/2024, 5:32 PM