Using ETL checkpoints in Glue for resilience
In modern data pipelines, resilience and fault tolerance are critical. Enterprises rely on robust ETL (Extract, Transform, Load) processes to move and prepare data across platforms reliably. AWS Glue, a fully managed serverless ETL service, provides scalable data integration. One essential technique to make Glue jobs more resilient and fault-tolerant is by using ETL checkpoints.
In this blog, we’ll explore how to implement ETL checkpoints in AWS Glue, and how they improve resilience, especially in long-running or failure-prone jobs.
๐ง What Are ETL Checkpoints?
ETL checkpoints refer to intermediate save points in your ETL process. They allow you to persist processed data at various stages of the pipeline so that if a job fails, you can resume from the last successful step rather than restarting from scratch. In AWS Glue, you can implement checkpoints manually by writing intermediate datasets to Amazon S3 or a database before proceeding to the next transformation or load step.
๐ Why Use Checkpoints in Glue?
Glue jobs may fail due to:
Data quality issues
Timeouts or memory limits
Schema mismatches
External service errors
Checkpoints provide partial recovery, reduce data reprocessing time, and support incremental loading. They're especially useful in long-running or multi-stage jobs.
✅ When to Use Checkpoints
Use ETL checkpoints when:
You’re processing large datasets in stages
You’re running Glue jobs on a schedule or in batches
Downstream transformations depend on successful prior steps
You need to debug complex ETL logic without rerunning the entire job
๐ ️ How to Implement ETL Checkpoints in AWS Glue
Let’s walk through a sample scenario using Glue’s PySpark interface:
Step 1: Read and Clean Raw Data
python
raw_df = glueContext.create_dynamic_frame.from_catalog(
database="sales_db",
table_name="raw_transactions"
)
cleaned_df = raw_df.drop_fields(["unnecessary_column"])
Step 2: Save Intermediate Checkpoint
python
glueContext.write_dynamic_frame.from_options(
frame=cleaned_df,
connection_type="s3",
connection_options={"path": "s3://my-etl-checkpoints/cleaned/"},
format="parquet"
)
This saves your progress. If a failure happens later, you can resume from this checkpoint.
Step 3: Load from Checkpoint (Optional Restart)
python
checkpoint_df = glueContext.create_dynamic_frame.from_options(
connection_type="s3",
connection_options={"paths": ["s3://my-etl-checkpoints/cleaned/"]},
format="parquet"
)
Step 4: Perform Transformation and Load to Target
python
transformed_df = ApplyMapping.apply(frame=checkpoint_df, mappings=[
("order_id", "string", "order_id", "string"),
("amount", "double", "order_total", "double")
])
glueContext.write_dynamic_frame.from_catalog(
frame=transformed_df,
database="analytics_db",
table_name="final_sales"
)
๐ Best Practices
Use partitioned S3 paths (e.g., by date) for checkpoints to keep data organized.
Clean up outdated checkpoints using AWS Lambda or lifecycle rules.
Store metadata logs about checkpoint creation (e.g., timestamp, record count) in DynamoDB for tracking.
Enable job bookmarks if suitable — AWS Glue provides bookmarks for automatic tracking of previously processed data.
๐งช Limitations
Checkpoints consume storage — balance cost vs. recovery needs.
Manual checkpointing requires additional logic.
AWS Glue job bookmarks can conflict with manual checkpoints if not managed properly.
๐ Conclusion
ETL checkpoints in AWS Glue are a practical strategy to improve the resilience and efficiency of data pipelines. By saving intermediate data stages, you reduce risk, avoid unnecessary reprocessing, and speed up recovery after failures. Whether you’re handling large datasets or mission-critical ETL workflows, incorporating checkpoints is a smart move for robust data engineering on AWS.
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