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📈 Prometheus Metrics Export

Monitoring real-time application throughput, request latencies, and error rates requires exporting metrics to monitoring platforms like Prometheus and Grafana.

ferrox-metrics initializes a Prometheus HTTP exporter running on a dedicated telemetry listener port.

1. Initializing Prometheus Exporter​

Call setup_metrics during application bootstrap:

use ferrox_metrics::{setup_metrics, record_http_request};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Starts Prometheus HTTP listener on port 9000
    setup_metrics()?;

    println!("📊 Prometheus metrics available at http://0.0.0.0:9000/metrics");
    Ok(())
}

2. Pre-Registered Metric Counters​

ferrox-metrics pre-registers standard counters:

Metric NameTypeDescription
http_requests_totalCounterTotal number of HTTP requests processed
db_queries_totalCounterTotal number of database queries executed
events_published_totalCounterTotal number of domain events published

3. Incrementing Counters in Controllers​

Increment counters using helper functions or standard metrics macros:

use ferrox_metrics::record_http_request;
use metrics::counter;

pub async fn my_controller_handler() {
    record_http_request();
    counter!("orders_created_total").increment(1);
}

4. Scraping /metrics Output​

curl http://localhost:9000/metrics

Output:

# HELP http_requests_total Total number of HTTP requests processed
# TYPE http_requests_total counter
http_requests_total 15420

\n\n---\n\n## 1. Philosophy / Purpose\n\nDocument the philosophy and core purpose of this component here.\n\n## 2. Architectural Layering\n\nExplain where this component sits within the Onion Architecture (e.g., Domain, Application, Infrastructure, or Presentation). \n\n## 3. How it Works (Under the hood)\n\nDetail the internal mechanics, memory model, and execution flow.\n\n## 4. Why it was designed this way\n\nExplain the historical context, trade-offs, and design rationale.\n\n## 5. Usage Guide & Code Examples\n\nProvide integration examples, setup guides, and typical use cases.\n\n## 6. Anti-Patterns\n\nList common mistakes, misconfigurations, and patterns to avoid when using this component.\n\n## 7. Pro-Tips / Best Practices\n\nProvide advanced tips, performance optimizations, and recommended patterns.