go-aws-emf

Go library for generating AWS CloudWatch Embedded Metric Format (EMF) JSON logs. Publish custom CloudWatch metrics directly from structured logs — no CloudWatch SDK or agent required.

Why use it

CloudWatch EMF lets you embed custom metrics inside log events. Instead of making separate PutMetricData API calls, you write a specially formatted JSON log line and CloudWatch extracts the metrics automatically. This library handles the EMF JSON structure so you don’t have to.

Zero external dependencies (stdlib only)
Full validation against the AWS EMF schema
Multiple dimensions and metrics per log entry
High-resolution metrics (1-second resolution) support

Quick start

go get github.com/zlatkoc/go-aws-emf/pkg/emf

Basic usage

metricLog := emf.NewMetricLog("MyApplicationMetrics")

metricLog.PutDimension("ServiceName", "UserService")
metricLog.PutDimension("Environment", "Production")

metricLog.WithDimensionSet([]string{"ServiceName"})
metricLog.WithDimensionSet([]string{"ServiceName", "Environment"})

metricLog.PutMetric("Latency", 42.0, emf.UnitMilliseconds)
metricLog.PutMetric("RequestCount", 1, emf.UnitCount)

fmt.Println(metricLog.String())

Builder pattern

metricLog := emf.NewMetricLog("MyApplicationMetrics")

metricLog.Builder().
    Dimension("ServiceName", "UserService").
    Dimension("Environment", "Production").
    DimensionSet([]string{"ServiceName"}).
    DimensionSet([]string{"ServiceName", "Environment"}).
    Metric("Latency", 42.0, emf.UnitMilliseconds).
    Metric("RequestCount", 1, emf.UnitCount).
    Property("RequestId", "12345").
    Build()

fmt.Println(metricLog.String())