Ephemeral Storage & /tmp in AWS Lambda

Overview

AWS Lambda provides a serverless compute service that allows you to run your code without provisioning or managing servers. One key aspect of Lambda functions is their temporary or ephemeral storage, which is used for various purposes during function execution.

What is Ephemeral Storage?

Ephemeral storage refers to temporary storage that is available for the duration of a process. In AWS Lambda, this storage is located in the /tmp directory and is limited in size.

Key Characteristics

• Temporary storage that lasts only for the duration of the Lambda invocation.
• Useful for data processing tasks that require temporary file storage.
• Storage is automatically cleaned up after the function execution ends.

Understanding /tmp in Lambda

The /tmp directory is the Linux file system's temporary storage location. In AWS Lambda, this allows your function to write files during execution.

Accessing /tmp

To access /tmp in your Lambda function, you can use standard file operations in your programming language of choice. Here’s an example in Python:

import os

def lambda_handler(event, context):
    # Write a temporary file in /tmp
    file_path = '/tmp/my_temp_file.txt'
    with open(file_path, 'w') as f:
        f.write('Hello, Lambda!')
    
    # Read the file back
    with open(file_path, 'r') as f:
        content = f.read()
    
    return {
        'statusCode': 200,
        'body': content
    }

Use Cases

Ephemeral storage in AWS Lambda can be utilized in various scenarios, including:

1. Data Processing: Storing intermediate results while processing large datasets.
2. File Manipulation: Temporarily storing files before uploading them to S3 or other services.
3. Cache: Storing transient data that does not need to persist beyond the function execution.

Best Practices

• Limit the use of ephemeral storage to necessary tasks to optimize performance.
• Regularly clean up files in /tmp to avoid reaching storage limits.
• Monitor your Lambda function’s ephemeral storage usage through AWS CloudWatch.

FAQ