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.


๐Ÿง  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.


๐Ÿ” 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


๐Ÿ› ️ 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"

)


๐Ÿ“Š 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.


๐Ÿงช 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.


๐Ÿš€ 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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