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What is AWS Glue Crawler Cost: AWS::Glue::Crawler | Use Cases

adminMay 9, 2024

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AWS Glue Crawler is a script that scans data stores, AWS Glue Crawler is a script that scans data sources, extracts metadata, and generates table definitions in the AWS Glue Data Catalog. It is the primary method used by AWS Glue users to populate the Data Catalog with tables. The crawler can analyze multiple data stores in a single run and automatically create or update tables in the Data Catalog based on the metadata it gathers.

What is AWS Glue Crawler

The AWS Glue Crawler is a powerful tool and the main method employed by AWS Glue users to populate the AWS Glue Data Catalog with tables. By running the crawler, multiple data stores can be crawled in a single execution, resulting in the creation or update of one or more tables in the Data Catalog.

What is AWS Glue Crawler

Here’s how it Glue crawler works:

1. Crawling Process:

- A crawler scans your data sources (such as Amazon S3, RDS, or other databases) to understand their structure and metadata.
- It identifies data formats, schemas, and properties.
- The crawler then creates or updates tables in the Data Catalog based on this information.

2. Data Catalog Tables:

- These tables serve as sources and targets for ETL (Extract, Transform, Load) jobs defined in AWS Glue.
- ETL jobs read from and write to the data stores specified in these tables.

3. Benefits of Crawlers:

- Automation: Crawlers automate the process of discovering and cataloging data, saving you time and effort.
- Flexibility: You can use crawlers to scan multiple data stores in a single run.
- Metadata Management: The Glue Catalog provides a centralized metadata repository for your data.

4. Usage:

- To add a crawler, configure it using the AWS Glue console.
- Run the crawler to extract metadata from your data sources.
- View the resulting tables in the Data Catalog.

Remember, crawlers are essential for managing and organizing your data, making it easier to work with in AWS Glue!

What are the Limitations of AWS Glue Crawlers?

While AWS Glue crawlers simplify data cataloging, understanding their limitations helps you make informed decisions! Here are some limitations of AWS Glue crawlers:

1. Customization Work:

- While AWS Glue crawlers automate data discovery and schema inference, customizing the crawling behavior can be challenging.
- You might need to fine-tune settings or write custom classifiers for specific data formats.

2. Integration with Other Platforms:

- AWS Glue might not seamlessly integrate with all external platforms or tools.
- Consider compatibility and potential workarounds when integrating with other services.

3. Real-Time Data Limitations:

- AWS Glue crawlers are primarily designed for batch processing.
- Real-time data ingestion might require additional solutions beyond Glue.

4. Required Skillset:

- Users need to understand data formats, schemas, and AWS Glue concepts.
- Some technical expertise is necessary for effective use.

5. Database Support:

- While Glue supports various data sources, certain databases might have limitations.
- For example, Oracle Database and MySQL don’t support schemas in the path.

6. Process Speed and Flexibility:

- Crawling large datasets can take time.
- Balancing speed and flexibility (e.g., depth of traversal) is essential.

7. Lack of Use Cases and Documentation:

- Some users find limited examples or documentation for specific scenarios.
- Exploring community forums and experimenting with Glue can help overcome this.

What are the Best Practices When Using AWS Glue Crawlers?

When using AWS Glue crawlers, consider the following best practices:

1. Use Fewer Files for Tables:

- To build tables and bootstrap your data lake, use fewer files.
- Reducing the number of files can improve performance and save costs.

2. Optimize Crawler Usage:

- Minimize the number of crawlers you run to save costs.
- Consider using AWS Glue APIs or Hive DDLs to manage data catalog tables.

3. Manage Partitions Efficiently:

- Use AWS Glue APIs to manage partitions.
- Proper partitioning improves query performance in downstream tools like Amazon Athena.

4. Sync Partition Schema:

- Avoid “HIVE_PARTITION_SCHEMA_MISMATCH” errors by keeping partition schemas in sync.
- Ensure consistency between the data catalog and actual data.

5. Update Table Metadata:

- Regularly update metadata for your tables.
- Accurate metadata helps downstream tools understand your data better.

6. Working with CSV Files:

- If dealing with CSV files, consider the following:
  - Ensure CSV data is enclosed in quotes.
  - Handle CSV files with headers appropriately.

Remember these practices to optimize your AWS Glue crawlers and enhance your data workflows! 😊🚀

How do I Handle Schema Evolution with Glue Crawlers?

AWS Glue Crawlers

When dealing with schema evolution in AWS Glue crawlers, it’s essential to follow best practices to ensure consistent data cataloging and smooth transitions. Here are some recommendations:

1. Maintain a Centralized Data Catalog:

- Use AWS Glue to create and manage a centralized Data Catalog that stores metadata and schema information.
- Regularly update the Data Catalog to reflect changes in data sources and schema definitions.

2. Database, Table, and Column Names:

- When creating schema in AWS Glue for querying in Athena, consider the following:
  - Database, table, and column names must be valid UTF-8 strings.
  - Avoid names less than 1 or more than 255 bytes long.
  - Characters allowed include spaces (but avoid leading spaces).
  - Be cautious when using auto-generated database names.

3. Using AWS Glue Crawlers:

- Crawlers automatically discover schema from your data sources and register them as tables in the Data Catalog.
- They can also detect and register partitions.
- Define crawlers to keep your Data Catalog and Amazon S3 in sync.

4. Syncing Partition Schema:

- To avoid “HIVE_PARTITION_SCHEMA_MISMATCH” errors, ensure consistent partition schemas.
- Use AWS Glue APIs to manage partitions effectively.

5. Updating Table Metadata:

- Regularly update metadata for your tables.
- Accurate metadata helps downstream tools understand your data better.

6. Working with CSV Files:

- If dealing with CSV files:
  - Ensure CSV data is enclosed in quotes.
  - Handle CSV files with headers appropriately.

Remember these practices to handle schema evolution effectively in AWS Glue crawlers! 😊🚀

AWS Glue Crawler Pricing:

Crawlers incur charges at a rate of $0.44 per DPU-Hour. For example, if you run a crawler with 2 DPUs for half an hour, you would be billed $0.44. Similarly, if you generate statistics on Glue tables and the process takes 10 minutes with 1 DPU, you would be charged approximately $0.07

How to Create Terraform Glue Crawler:

In Terraform, you can use the aws_glue_crawler a resource to define and manage an AWS Glue crawler. Here’s an example of how to create a AWS Glue crawler terraform:

resource “aws_glue_crawler” “example_crawler” {
name = “example-crawler”
role = aws_iam_role.crawler_role.arn
database_name = aws_glue_catalog_database.example_db.name
targets {
s3_targets {
path = “s3://example-bucket/data/”
}}
schedule {
schedule_expression = “cron(0 0 * * ? *)”
}}

In this example, the aws_glue_crawler the resource creates a crawler named “example-crawler”. It specifies the IAM role for the crawler, the Glue database it will populate, and the target location of the data (in this case, an S3 bucket). It also sets a schedule for the crawler to run daily at midnight.

In this example, the AWS::Glue::Crawler resource creates a crawler named “MyCrawler”. It specifies the IAM role for the crawler, the Glue database it will populate, and the target location of the data (an S3 bucket). It also sets a schedule for the crawler to run daily at midnight using a cron expression.

CDK Glue Crawler:

CDK Glue Crawler

In AWS CDK (Cloud Development Kit), you can use the glue.CfnCrawler construct to define and deploy an AWS Glue crawler. Here’s an example of how to create a Glue crawler using CDK:

import * as glue from ‘@aws-cdk/aws-glue’;
import * as cdk from ‘@aws-cdk/core’;

const app = new cdk.App();
const stack = new cdk.Stack(app, ‘MyStack’);

const crawler = new glue.CfnCrawler(stack, ‘MyCrawler’, {
name: ‘MyCrawler’,
role: ‘arn:aws:iam::123456789012:role/my-crawler-role’,
databaseName: ‘my-database’,
targets: {
s3Targets: [{
path: ‘s3://my-bucket/data/’
}]
},
schedule: {
scheduleExpression: ‘cron(0 0 * * ? *)’
}
});

app.synth();

In this example, the glue.CfnCrawler construct creates a crawler named “MyCrawler”. It specifies the IAM role for the crawler, the Glue database it will populate, and the target location of the data (an S3 bucket). It also sets a schedule for the crawler to run daily at midnight using a cron expression.

AWS Glue vs Athena

The AWS Glue Data Catalog is responsible for storing and managing metadata information about data sources, tables, and their schemas. When a new table schema is created, Athena, which utilizes Apache Hive, uses the Data Catalog to define tables and store their schemas. Athena is particularly well-suited for ad-hoc querying and data analysis tasks.

AWS Glue Interview Questions:

Here are some commonly asked interview questions about AWS Glue:

What is AWS Glue, and what are its key features?
What is the purpose of the AWS Glue Data Catalog?
How does AWS Glue handle schema evolution in data sources?
Explain the concept of a Glue Crawler and its role in AWS Glue.
What is the difference between AWS Glue ETL and AWS Glue DataBrew?
How does AWS Glue handle incremental data processing and data deduplication?
What are the benefits of using AWS Glue over traditional ETL processes?
How do you handle errors and exceptions in AWS Glue ETL jobs?
What is the underlying technology used by AWS Glue for ETL processing?
Can you explain the difference between AWS Glue and AWS Athena?
How do you monitor and troubleshoot AWS Glue jobs?
What are the security and compliance considerations when using AWS Glue?
Discuss the pricing model and factors influencing the cost of using AWS Glue.
Can you explain how AWS Glue integrates with other AWS services like Amazon S3, Amazon Redshift, and Amazon RDS?
Share an example of a complex ETL job you have implemented using AWS Glue.