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Logging output from AWS Lambda functions

Like most other application logs, Lambda function logging from CloudWatch logs provides valuable information that can be used during an investigation to facilitate answering questions about the functions behavior and health. Use this procedure to search all CloudWatch logs collected for a specific Lambda function.

Data required 

AWS CloudWatch data

Procedure

  1. Configure the Splunk Add-on for Amazon Web Services.
  2. Ensure that your deployment is ingesting AWS data through one of the following methods:
    • Pulling the data from Splunk via AWS APIs. At small scale, pull via the AWS APIs will work fine.
    • Pushing the data from AWS into Splunk via Lambda/Firehose to Splunk HTTP event collector. As the size and scale of either your AWS accounts or the amount of data to be collected grows, pushing data from AWS into Splunk is the easier and more scalable method.
  3. Run the following search. You can optimize it by specifying an index and adjusting the time range.
index="<AWS index name>" sourcetype="aws:cloudwatchlogs" source="*/aws/lambda/*" 
source="*<Lambda function name>*"

Search explanation

The table provides an explanation of what each part of this search achieves. You can adjust this query based on the specifics of your environment.

Splunk Search Explanation
index="<AWS index name>" sourcetype="aws:cloudwatchlogs" Search the index(s) where AWS data is stored, filtered to just the AWS Cloudwatch logs.
source="*/aws/lambda/*" 
source="*<Lambda function name>*"
Filter results to those associated to a given Lambda function.

Next steps

In the search, add additional keywords relevant to the investigation. For instance, adding (error OR fail*) to the search might help uncover problems occurring with the Lambda function.

You might also be interested in other processes associated with the Managing an Amazon Web Services environment use case.