Overview

Extensions for the aws-embedded-metrics npm module, adding flatcount metrics that emit a total count instead of an array of each individual count, and the ability to disable metrics without removing metrics method calls.

Installation

The package is available on npm as @shutterstock/aws-embedded-metrics-flatten

npm i @shutterstock/aws-embedded-metrics-flatten

Importing

import { FlatCountMetrics, metricScopeDummy } from '@shutterstock/aws-embedded-metrics-flatten';
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Features

• Flattens count metrics into a single emitted line
  • This works around the max length limitation of CloudWatch Embedded Metrics log messages
  • Rather than emitting an array, such as [1, 1, 1, 1, 1], it emits a single count of [5], dramatically reducing the size of the log message when counting thousands of iterations in a Lambda function
• Gives the ability to disable the metrics without having to protect each metric emit with a conditional

Flattening Count Metrics

CloudWatch embedded metrics (parsed from CloudWatch logs) have a limit of something like 1,000 items in a metrics log statement. Metrics beyond that point will be ignored.

aws-embedded-metrics will emit metrics with 10,000 calls to .putMetric('MyMetric', 1, metricUnit.Count); as an array with 10,000 elements all with the value of 1... and about 9,000 of those will get ignored as a result.

Optional Metrics

metricScopeDummy is a replacement for metricScope that will pass an MetricsLoggerDummy instance instead of a MetricsLogger instance to the callback function. MetricsLoggerDummy implements the same interface as MetricsLogger but it does not accumulate data and does not emit any logs.

Coupled with a configuration setting / env var it is possible to emit metrics or not emit metrics by changing which function is used to create the metrics object.

Contributing

Setting up Build Environment

• nvm use
• npm i
• npm run build
• npm run lint
• npm run test

Running Examples

metrics-flatten

1. npm run example:metrics-flatten
   1. Will print 2 lines of metrics
   2. MyFlatMetric will have a single value of 10000
2. FLATTEN_METRICS=false npm run example:metrics-flatten
   1. Will print many lines of metrics
   2. MyFlatMetric will have 10,000 values of 1 across many different lines

metrics-optional

1. npm run example:metrics-optional
   1. Metrics will print
2. EMIT_METRICS=false npm run example:metrics-optional
   1. Metrics will not print