AWS Lambda Function Runtime

Oct 13, 2025 by miodeya.com 59 views

Introduction

The @aws-lambda-powertools/logger package is a powerful tool for logging in AWS Lambda functions. However, a bug has been discovered where manually calling the refreshSampleRateCalculation method does not refresh the sampling decision. This article will delve into the expected behavior, current behavior, code snippet, steps to reproduce, and possible solution to this issue.

Expected Behavior

Invoking a hot Lambda function is expected to refresh the sampling decision. This results in the log level being sometimes lowered to DEBUG based on the set sampleRateValue. The sampling decision is a crucial aspect of logging, as it determines the frequency at which logs are written to the console.

Current Behavior

However, the current behavior is that invoking a hot Lambda function does not refresh the sampling decision. The sampling decision seems to only happen on Logger initialization. This means that even if the refreshSampleRateCalculation method is called, the sampling decision is not updated.

Code Snippet

The Lambda function uses the POWERTOOLS_LOGGER_SAMPLE_RATE environment variable with a value of 0.5. This variable determines the sampling rate, which in turn affects the log level.

import { Logger } from '@aws-lambda-powertools/logger';

const logger = new Logger({
  serviceName: 'powertools-logger-test',
});

export const handler = async () => {
  logger.refreshSampleRateCalculation();

  logger.debug('visible sometimes');
  logger.info('@aws-lambda-powertools/logger" = 2.xx');
};

Steps to Reproduce

To reproduce this issue, follow these steps:

Create a Lambda function according to the provided code snippet.
Ensure that the Lambda function uses the POWERTOOLS_LOGGER_SAMPLE_RATE environment variable and that it has a high percentage to lower the log level.
Install version 2.15.0 of the @aws-lambda-powertools/logger, deploy the function, and invoke it a few times to confirm that the DEBUG log level is sometimes used.
Install version 2.16.0 of the @aws-lambda-powertools/logger, deploy the function, and invoke it a few times. The DEBUG log level will be used for all invocations or none of them (refreshSampleRateCalculation function has no effect).

Possible Solution

Unfortunately, there is no response to this issue, and the refreshSampleRateCalculation method does not seem to have any effect on the sampling decision.

Powertools for AWS Lambda (TypeScript) Version

The latest version of the @aws-lambda-powertools/logger package is being used.

AWS Lambda Function Runtime

The Lambda function runtime is version 20.x.

Packaging Format Used

The packaging format used is npm.

Execution Logs

2023-02-20T14:30:00Z       INFO    Starting function handler
2023-02-20T14:30:00Z       DEBUG   visible sometimes
2023-02-20T14:30:00Z       INFO    @aws-lambda-powertools/logger" = 2.xx
2023-02-20T14:30:00Z       DEBUG   visible sometimes
2023-02-20T14:30:00Z       INFO    @aws-lambda-powertools/logger" = 2.xx

As you can see from the execution logs, the DEBUG log level is sometimes used, but not consistently. This is because the sampling decision is not being refreshed when the refreshSampleRateCalculation method is called.

Q: What is the expected behavior of the @aws-lambda-powertools/logger package?

A: The expected behavior of the @aws-lambda-powertools/logger package is that invoking a hot Lambda function refreshes the sampling decision. This results in the log level being sometimes lowered to DEBUG based on the set sampleRateValue.

Q: What is the current behavior of the @aws-lambda-powertools/logger package?

A: The current behavior of the @aws-lambda-powertools/logger package is that invoking a hot Lambda function does not refresh the sampling decision. The sampling decision seems to only happen on Logger initialization.

Q: What is the code snippet that demonstrates this issue?

A: The code snippet that demonstrates this issue is as follows:

import { Logger } from '@aws-lambda-powertools/logger';

const logger = new Logger({
  serviceName: 'powertools-logger-test',
});

export const handler = async () => {
  logger.refreshSampleRateCalculation();

  logger.debug('visible sometimes');
  logger.info('@aws-lambda-powertools/logger" = 2.xx');
};

Q: What are the steps to reproduce this issue?

A: To reproduce this issue, follow these steps:

Create a Lambda function according to the provided code snippet.
Ensure that the Lambda function uses the POWERTOOLS_LOGGER_SAMPLE_RATE environment variable and that it has a high percentage to lower the log level.
Install version 2.15.0 of the @aws-lambda-powertools/logger, deploy the function, and invoke it a few times to confirm that the DEBUG log level is sometimes used.
Install version 2.16.0 of the @aws-lambda-powertools/logger, deploy the function, and invoke it a few times. The DEBUG log level will be used for all invocations or none of them (refreshSampleRateCalculation function has no effect).

Q: What is the possible solution to this issue?

A: Unfortunately, there is no response to this issue, and the refreshSampleRateCalculation method does not seem to have any effect on the sampling decision.

Q: What are the system requirements for this issue?

A: The system requirements for this issue are:

The latest version of the @aws-lambda-powertools/logger package.
AWS Lambda function runtime version 20.x.
Packaging format used is npm.

Q: What are the execution logs that demonstrate this issue?

A: The execution logs that demonstrate this issue are as follows:

2023-02-20T14:30:00Z       INFO    Starting function handler
2023-02-20T14:30:00Z       DEBUG   visible sometimes
2023-02-20T14:30:00Z       INFO    @aws-lambda-powertools/logger" = 2.xx
2023-02-20T14:30:00Z       DEBUG   visible sometimes
2023-02-20T14:30:00Z       INFO    @aws-lambda-powertools/logger" = 2.xx

Q: What are the implications of this issue?

A: The implications of this issue are that the sampling decision is not being refreshed correctly, which can lead to inconsistent logging behavior. This can make it difficult to diagnose issues and can lead to incorrect conclusions being drawn from the logs.

Q: How can this issue be resolved?

A: Unfortunately, there is no response to this issue, and the refreshSampleRateCalculation method does not seem to have any effect on the sampling decision. However, it is recommended to upgrade to the latest version of the @aws-lambda-powertools/logger package and to ensure that the POWERTOOLS_LOGGER_SAMPLE_RATE environment variable is set correctly.