metricscloudwatchembedded

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

```rust let metrics = metricscloudwatchembedded::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: toml metrics_cloudwatch_embedded = { version = "0.3", features = ["lambda"] }

```rust use lambdaruntime::{Error, LambdaEvent}; use metricscloudwatch_embedded::lambda::handler::run; use serde::{Deserialize, Serialize};

[derive(Deserialize)]

struct Request {}

[derive(Serialize)]

struct Response { }

async fn functionhandler(event: LambdaEvent<()>) -> Result { metrics::incrementcounter!("requests", "Method" => "Default");

Ok( Response {})

}

[tokio::main]

async fn main() -> Result<(), Error> { tracingsubscriber::fmt() .withenvfilter(tracingsubscriber::filter::EnvFilter::fromdefaultenv()) .withtarget(false) .withouttime() .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

• Simon Andersson (ramn) and contributors - For the metrics_cloudwatch crate I used as a reference
• Toby Lawrence (tobz) - For answering my metrics crate questions before I even had something working