Portable monitoring package for Rust servers, exposing metric and healthcheck endpoints

What

Holter is intended to be a simple implementation of web-based monitoring metrics scraping and healthcheck endpoints. It creates a small Axum webserver with a /metrics and a /healthz endpoint for exporing Prometheus metrics for scraping (collected in rust by the metrics crate) as well as a healthcheck endpoint for monitoring availability and health behind automated infra solutions such as Kubernetes container orchestration (when wrapped in a container HEALTHCHECK) or when fronted by an application load balancer.

How

By default, the server listens on the local 127.0.0.1 address at the default Prometheus port 9090 but this can be configured by passing it a std::netSocketAddr at startup. The service can also be configured, via the db feature to monitor the ability to reach any database supported by sqlx by pinging the database on each healthcheck endpoint request.

Features

• default: bare bones metrics and healthz rest endpoints
• db: monitoring of a sqlx database connection
• api-metrics: provides a tower middleware that, when injected into an axum router, measures and returns request/response latency histograms and invocation counts on all endpoints served by the router.