Monitoring Apache Iceberg metadata layer using AWS Lambda, AWS Glue, and AWS CloudWatch

In the era of big data, data lakes have emerged as a cornerstone for storing vast amounts of raw data in its native format. They support structured, semi-structured, and unstructured data, offering a flexible and scalable environment for data ingestion from multiple sources. Data lakes provide a unified repository for organizations to store and use large volumes of data. This enables more informed decision-making and innovative insights through various analytics and machine learning applications.

Despite their advantages, traditional data lake architectures often grapple with challenges such as understanding deviations from the most optimal state of the table over time, identifying issues in data pipelines, and monitoring a large number of tables. As data volumes grow, the complexity of maintaining operational excellence also increases. Monitoring and tracking issues in the data management lifecycle are essential for achieving operational excellence in data lakes.

This is where Apache Iceberg comes into play, offering a new approach to data lake management. Apache Iceberg is an open table format designed specifically to improve the performance, reliability, and scalability of data lakes. It addresses many of the shortcomings of traditional data lakes by providing features such as ACID transactions, schema evolution, row-level updates and deletes, and time travel.

In this blog post, we’ll discuss how the metadata layer of Apache Iceberg can be used to make data lakes more efficient. You will learn about an open-source solution that can collect important metrics from the Iceberg metadata layer. Based on collected metrics, we will provide recommendations on how to improve the efficiency of Iceberg tables. Additionally, you will learn how to use Amazon CloudWatch anomaly detection feature to detect ingestion issues.

Deep dive into Iceberg’s Metadata layer

Before diving into a solution, let’s understand how the Apache Iceberg metadata layer works. The Iceberg metadata layer provides an open specification instructing integrated big data engines such as Spark or Trino how to run read and write operations and how to resolve concurrency issues. It’s crucial for maintaining inter-operability between different engines. It stores detailed information about tables such as schema, partitioning, and file organization in versioned JSON and Avro files. This ensures that each change is tracked and reversible, enhancing data governance and auditability.

History and versioning: Iceberg’s versioning feature captures every change in table metadata as immutable snapshots, facilitating data integrity, historical views, and rollbacks.

File organization and snapshot management: Metadata closely manages data files, detailing file paths, formats, and partitions, supporting multiple file formats like Parquet, Avro, and ORC. This organization helps with efficient data retrieval through predicate pushdown, minimizing unnecessary data scans. Snapshot management allows concurrent data operations without interference, maintaining data consistency across transactions.

In addition to its core metadata management capabilities, Apache Iceberg also provides specialized metadata tables—snapshots, files, and partitions—that provide deeper insights and control over data management processes. These tables are dynamically generated and provide a live view of the metadata for query purposes, facilitating advanced data operations:

• Snapshots table: This table lists all snapshots of a table, including snapshot IDs, timestamps, and operation types. It enables users to track changes over time and manage version history effectively.
• Files table: The files table provides detailed information on each file in the table, including file paths, sizes, and partition values. It is essential for optimizing read and write performance.
• Partitions table: This table shows how data is partitioned across different files and provides statistics for each partition, which is crucial for understanding and optimizing data distribution.

Metadata tables enhance Iceberg’s functionality by making metadata queries straightforward and efficient. Using these tables, data teams can gain precise control over data snapshots, file management, and partition strategies, further improving data system reliability and performance.

Before you get started

The next section describes a packaged open source solution using Apache Iceberg’s metadata layer and AWS services to enhance monitoring across your Iceberg tables.

Before we deep dive into the suggested solution, let’s mention Iceberg MetricsReporter, which is a native way to emit metrics for Apache Iceberg. It supports two types of reports: one for commits and one for scans. The default output is log based. It produces log files as a result of commit or scan operations. To submit metrics to CloudWatch or any other monitoring tool, users need to create and configure a custom MetricsReporter implementation. MetricsReporter is supported in Apache Iceberg v1.1.0 and later versions, and customers who want to use it must enable it through Spark configuration on their existing pipelines.

The following is deployed independently and doesn’t require any configuration changes to existing data pipelines. It can immediately start monitoring all the tables within the AWS account and AWS Region where it’s deployed. This solution introduces an additional latency of metrics arrival between 20 and 80 seconds compared to MetricsReporter but offers seamless integration without the need for custom configurations or changes to current workflows.

Solution overview

This solution is specifically designed for customers who run Apache Iceberg on Amazon Simple Storage Service (Amazon S3) and use AWS Glue as their data catalog.

Key features

This solution uses an AWS Lambda deployment package to collect metrics from Apache Iceberg tables. The metrics are then submitted to CloudWatch where you can create metrics visualizations to help recognize trends and anomalies over time.

The solution is designed to be lightweight, focusing on collecting metrics directly from the Iceberg metadata layer without scanning the actual data layer. This approach significantly reduces the compute capacity required, making it efficient and cost-effective. Key features of the solution include:

• Time-series metrics collection: The solution monitors Iceberg tables continuously to identify trends and detect anomalies in data ingestion rates, partition skewness, and more.
• Event-driven architecture: The solution uses Amazon EventBridge to launch a Lambda function when the state of an AWS Glue Data Catalog table changes. This ensures real-time metrics collection every time a transaction is committed to an Iceberg table.
• Efficient data retrieval: Incorporates minimal compute resources by utilizing AWS Glue interactive sessions and the pyiceberg library to directly access Iceberg metadata tables such as snapshots, partitions, and files.

Metrics tracked

As of the blog release date, the solution collects over 25 metrics. These metrics are categorized into several groups:

• Snapshot metrics: Include total and changes in data files, delete files, records added or removed, and size changes.
• Partition and file metrics: Aggregated and per-partition metrics like average, maximum, minimum record counts and file sizes, which help in understanding data distribution and help optimizing storage.

To see the complete list of metrics, go to the GitHub repository.

Visualizing data with CloudWatch dashboards

The solution also provides a sample CloudWatch dashboard to visualize the collected metrics. Metrics visualization is important for real-time monitoring and detecting operational issues. The provided helper script simplifies the set up and deployment of the dashboard.

You can go to the GitHub repository to learn more about how to deploy the solution in your AWS account.

What are the vital metrics for Apache Iceberg tables?

This section discusses specific metrics from Iceberg’s metadata and explains why they’re important for monitoring data quality and system performance. The metrics are broken down into three parts: insight, challenge, and action. This provides a clear path for practical application. In this section, we provide only a subset of the available metrics that the solution can collect, for a complete list, see the solution Github page.

1. snapshot.added_data_files, snapshot.added_records

• Metric insight: The number of data files and number of records added to the table during the last transaction. The ingestion rate measures the speed at which new data is added to the data lake. This metric helps identify bottlenecks or inefficiencies in data pipelines, guiding capacity planning and scalability decisions.
• Challenge: A sudden drop in the ingestion rate can indicate failures in data ingestion pipelines, source system outages, configuration errors or traffic spikes.
• Action: Teams need to establish real-time monitoring and alert systems to detect drops in ingestion rates promptly, allowing quick investigations and resolutions.

2. files.avg_record_count, files.avg_file_size

• Metric insight: These metrics provide insights into the distribution and storage efficiency of the table. Small file sizes might suggest excessive fragmentation.
• Challenge: Excessively small file sizes can indicate inefficient data storage leading to increased read operations and higher I/O costs.
• Action: Implementing regular data compaction processes helps consolidate small files, optimizing storage and enhancing content delivery speeds as demonstrated by a streaming service. Data Catalog offers automatic compaction of Apache Iceberg tables. To learn more about compacting Apache Iceberg tables, see Enable compaction in Working with tables on the AWS Glue console.

3. partitions.skew_record_count, partitions.skew_file_count

• Metric insight: The metrics indicate the asymmetry of the data distribution across the available table partitions. A skewness value of zero, or very close to zero, suggests that the data is balanced. Positive or negative skewness values might indicate a problem.
• Challenge: Imbalances in data distribution across partitions can lead to inefficiencies and slow query responses.
• Action: Regularly analyze data distribution metrics to adjust partitioning configuration. Apache Iceberg allows you to transform partitions dynamically, which enables optimization of table partitioning as query patterns or data volumes change, without impacting your existing data.

4. snapshot.deleted_records, snapshot.total_delete_files, snapshot.added_position_deletes

• Metric insight: Deletion metrics in Apache Iceberg provide important information on the volume and nature of data deletions within a table. These metrics help track how often data is removed or updated, which is essential for managing data lifecycle and compliance with data retention policies.
• Challenge: High values in these metrics can indicate excessive deletions or updates, which might lead to fragmentation and decreased query performance.
• Action: To address these challenges, run compaction periodically to ensure deleted rows do not persist in new files. Regularly review and adjust data retention policies and consider expiring old snapshots to keep only necessary amount of data files. You can run compaction operation on specific partitions using Amazon Athena Optimize

Effective monitoring is essential for making informed decisions about necessary maintenance actions for Apache Iceberg tables. Determining the right timing for these actions is crucial. Implementing timely preventative maintenance ensures high operational efficiency of the data lake and helps to address potential issues before they become significant problems.

Using Amazon CloudWatch for anomaly detection and alerts

This section assumes that you have completed the solution setup and collected operational metrics from your Apache Iceberg tables into Amazon CloudWatch.

Now you can start setting up some alerts and detect anomalies.

We guide you on setting up the anomaly detection and configuring alerts in CloudWatch to monitor the snapshot.added_records metric, which indicates the ingestion rate of data written into an Apache Iceberg table.

Set up anomaly detection

CloudWatch anomaly detection applies machine learning algorithms to continuously analyze system metrics, determine normal baselines, and identify items that are outside of the established patterns. Here is how you configure it:

1. Select Metrics: In the AWS Management Console for Cloudwatch, go to the Metrics  tab and search for and select snapshot.added_records.
2. Create anomaly detection models: Choose the Graphed metrics tab and click the Pulse icon to enable anomaly detection.
3. Set Sensitivity: The second parameter of the ANOMALY_DETECTION_BAND (m1, 5) is to adjust the sensitivity of the anomaly detection. The goal is to balance detecting real issues and reducing false positives.

Configure alerts

After the anomaly detection model is set up, set up an alert to notify operations teams about potential issues:

1. Create alarm: Choose the bell icon under Actions on the same Graphed metrics tab.
2. Alarm settings: Set the alarm to notify the operations team when the snapshot.added_records metric is outside the anomaly detection band for two consecutive periods. This helps reduce the risk of false alerts.
3. Alarm actions: Configure CloudWatch to send an alarm email to the operations team. In addition to sending emails, CloudWatch alarm actions can automatically launch remediation processes, such as scaling operations or initiating data compaction.

Best practices

• Regularly review and adjust models: As data patterns evolve, periodically review and adjust anomaly detection models and alarm settings to remain effective.
• Comprehensive coverage: Ensure that all critical aspects of the data pipeline are monitored, not just a few metrics.
• Documentation and communication: Maintain clear documentation of what each metric and alarm represent and ensure that your operations team understands the monitoring set up and response procedures. Set up the alerting mechanisms to send notifications through appropriate channels such as email, corporate messenger, or telephone to ensure your operations team stays informed and can quickly address the issues.
• Create playbooks and automate remediation tasks: Establish detailed playbooks that describe step-by-step responses for common scenarios identified by alerts. Additionally, automate remediation tasks where possible to speed up response times and reduce the manual burden on teams. This ensures consistent and effective responses to all incidents.

CloudWatch anomaly detection and alerting features help organizations proactively manage their data lakes. This ensures data integrity, reduces downtime, and maintains high data quality. As a result, it enhances operational efficiency and supports robust data governance.

Conclusion

In this blog post, we explored Apache Iceberg’s transformative impact on data lake management. Apache Iceberg addresses the challenges of big data with features like ACID transactions, schema evolution, and snapshot isolation, enhancing data reliability, query performance, and scalability.

We delved into Iceberg’s metadata layer and related metadata tables such as snapshots, files, and partitions that allow easy access to crucial information about the current state of the table. These metadata tables facilitate the extraction of performance-related data, enabling teams to monitor and optimize the data lake’s efficiency.

Finally, we showed you a practical solution for monitoring Apache Iceberg tables using Lambda, AWS Glue, and CloudWatch. This solution uses Iceberg’s metadata layer and CloudWatch monitoring capabilities to provide a proactive operational framework. This framework detects trends and anomalies, ensuring robust data lake management.

About the Author

Michael Greenshtein is a Senior Analytics Specialist at Amazon Web Services. He is an experienced data professional with over 8 years in cloud computing and data management. Michael is passionate about open-source technology and Apache Iceberg.