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Making the Most of AWS Lambda Logs

How can you get the most out of monitoring your AWS Lambda functions? In this post, we’ll take a look at the monitoring and logging data that Lambda makes available, and the value that it can bring to your AWS operations. You may be thinking, “Why should I even monitor AWS Lambda? Doesn’t AWS take care of all of the system and housekeeping stuff with Lambda? I thought that all the user had to do was write some code and run it!”

A Look at AWS Lambda

If that is what you’re thinking, then for the most part, you’re right. AWS Lambda is designed to be a simple plug-and-play experience from the user’s point of view. Its function is simply to run user-supplied code on request in a standardized environment. You write the code, specifying some basic configuration parameters, and upload the code, the configuration information, and any necessary dependencies to AWS Lambda. This uploaded package is called a Lambda function.

To run the function, you invoke it from an application running somewhere in the AWS ecosystem (EC2, S3, or most other AWS services). When Lambda receives the invoke request, it runs your function in a container; the container pops into existence, does its job, and pops back out of existence. Lambda manages the containers—You don’t need to (and can’t) do anything with them.

So there it is—Lambda. It’s simple, it’s neat, it’s clean, and it does have some metrics which can be monitored, and which are worth monitoring.

Which Lambda Metrics to Monitor?

So, which Lambda metrics are important, and why would you monitor them? There are two kinds of monitoring information which AWS Lambda provides: metrics displayed in the AWS CloudWatch console, and logging data, which is handled by both CloudWatch and the CloudTrail monitoring service. Both types of data are valuable to the user—the nature of that value and the best way to make use of it depend largely on the type of data.

Monitoring Lambda CloudWatch Console Metrics

Because AWS Lambda is strictly a standardized platform for running user-created code, the metrics that it displays in the CloudWatch console are largely concerned with the state of that code. These metrics include the number of invocation requests that a function receives, the number of failures resulting from errors in the function, the number of failures in user-configured error handling, the function’s duration, or running time, and the number of invocations that were throttled as a result of the user’s concurrency limits.

These are useful metrics, and they can tell you a considerable amount about how well the code is working, how well the invocations work, and how the code operates within its environment. They are, however, largely useful in terms of functionality, debugging, and day-to-day (or millisecond-to-millisecond) operations.

Monitoring and Analyzing AWS Lambda Logs

With AWS Lambda, logging data is actually a much richer source of information in many ways. This is because logging provides a cumulative record of actions over time, including all API calls made in connection with AWS Lambda. Since Lambda functions exist for the most part to provide support for applications and websites running on other AWS services, Lambda log data is the main source of data about how a function is doing its job.

“Logs,” you say, like Indiana Jones surrounded by hissing cobras. “Why does it always have to be logs? Digging through logs isn’t just un-fun, boring, and time-consuming. More often than not, it’s counter-productive, or just plain impractical!”

And once again, you’re right. There isn’t much point in attempting to manually analyze AWS Lambda logs. in fact, you have three basic choices: either ignore the logs, write your own script for extracting and analyzing log data, or let a monitoring and analytics service do the work for you. For the majority of AWS Lambda users, the third option is by far the most practical and the most useful.

Sumo Logic’s Log Analytics Dashboards for Lambda

To get a clearer picture of what can be done with AWS Lambda metrics and logging data, let’s take a look at how the Sumo Logic App for AWS Lambda extracts useful information from the raw data, and how it organizes that data and presents it to the user.

On the AWS side, you can use a Lambda function to collect CloudWatch logs and route them to Sumo Logic. Sumo integrates accumulated log and metric information to present a comprehensive picture of your AWS Lambda function’s behavior, condition, and use over time, using three standard dashboards:

The Lambda Overview Dashboard

The Overview dashboard provides a graphic representation of each function’s duration, maximum memory usage, compute usage, and errors. This allows you to quickly see how individual functions perform in comparison with each other.

The Overview dashboard also breaks duration, memory, and compute usage down over time, making it possible to correlate Lambda function activity with other AWS-based operations, and it compares the actual values for all three metrics with their predicted values over time. This last set of values (actual vs. predicted) can help you pinpoint performance bottlenecks and allocate system resources more efficiently.

The Lambda Duration and Memory Dashboard

Sumo Logic’s AWS Lambda Duration and Memory dashboard displays duration and maximum memory use for all functions over a 24-hour period in the form of both outlier and trend charts. The Billed Duration by Hour trend chart compares actual billed duration with predicted duration on an hourly basis.

In a similar manner, the Unused Memory trend chart shows used, unused, and predicted unused memory size, along with available memory. These charts, along with the Max Memory Used box plot chart, can be very useful in determining when and how to balance function invocations and avoid excessive memory over- or underuse.

The Lambda Usage Dashboard

The Usage dashboard breaks down requests, duration, and memory usage by function, along with requests by version alias. It includes actual request counts broken down by function and version alias.

The Usage dashboard also includes detailed information on each function, including individual request ID, duration, billing, memory, and time information for each request. The breakdown into individual requests makes it easy to identify and examine specific instances of a function’s invocation, in order to analyze what is happening with that function on a case-by-case level.

It is integrated, dashboard-based analytics such as those presented by the Sumo Logic App for AWS Lambda that make it not only possible but easy to extract useful data from Lambda, and truly make the most of AWS Lambda monitoring.

About the Author

Michael Churchman started as a scriptwriter, editor, and producer during the anything-goes early years of the game industry. He spent much of the ‘90s in the high-pressure bundled software industry, where the move from waterfall to faster release was well under way, and near-continuous release cycles and automated deployment were already de facto standards. During that time he developed a semi-automated system for managing localization in over fifteen languages. For the past ten years, he has been involved in the analysis of software development processes and related engineering management issues.

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