metrics_cloudwatch_embedded

The interface is not stable

This is a Minimum Viable Product for feedback, experimentation and iteration

Purpose

Provide a backend for the metrics facade crate, to emit metrics in CloudWatch Embedded Metrics Format

Simple Example

let metrics = metrics_cloudwatch_embedded::Builder::new()
    .cloudwatch_namespace("MyApplication")
    .init()
    .unwrap();

metrics::increment_counter!("requests", "Method" => "Default");

metrics
    .set_property("RequestId", "ABC123")
    .flush();

AWS Lambda Example

The Lambda Runtime intergration feature handles flushing metrics after each invoke via either run() alternatives or MetricService which inplements the tower::Service trait. It also provides optional helpers for emiting a metric on cold starts and decorating metric documents with request id and/or x-ray trace id.

In your Cargo.toml add:

metrics_cloudwatch_embedded = {  version = "0.3", features = ["lambda"] }

use lambda_runtime::{Error, LambdaEvent};
use metrics_cloudwatch_embedded::lambda::handler::run;
use serde::{Deserialize, Serialize};

#[derive(Deserialize)]
struct Request {}

#[derive(Serialize)]
struct Response {
}

async fn function_handler(event: LambdaEvent<()>) -> Result<Response, Error> {
    metrics::increment_counter!("requests", "Method" => "Default");

    Ok( Response {})
}

#[tokio::main]
async fn main() -> Result<(), Error> {
    tracing_subscriber::fmt()
        .with_env_filter(tracing_subscriber::filter::EnvFilter::from_default_env())
        .with_target(false)
        .without_time()
        .compact()
        .init();

    let metrics = metrics_cloudwatch_embedded::Builder::new()
        .cloudwatch_namespace("MetricsExample")
        .with_dimension("Function", std::env::var("AWS_LAMBDA_FUNCTION_NAME").unwrap())
        .lambda_cold_start_metric("ColdStart")
        .with_lambda_request_id("RequestId")
        .init()
        .unwrap();

    run(metrics, function_handler).await
}

Limitations

Histograms retain up to 100 values (the maximum for a single metric document) between calls to collector::Collector::flush, overflow will report an error via the tracing crate
Dimensions set at initialization via Builder::with_dimension(...) may not overlap with metric labels
Only the subset of metric units in metrics::Unit are supported https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_MetricDatum.html
Registering different metric types with the same metrics::Key will fail with an error via the tracing crate
The Embedded Metric Format supports a maximum of 30 dimensions per metric, attempting to register a metric with more than 30 dimensions/labels will fail with an error via the tracing crate

Thanks