feat(shared): Metrics Server Args

crates/shared/cli-utils/src/lib.rs

@@ -12,6 +12,9 @@ pub use backtrace::Backtracing;
 mod args;
 pub use args::GlobalArgs;
 
+mod metrics;
+pub use metrics::MetricsArgs;
+
 mod logging;
 pub use logging::{LogFormat, LogRotation, LoggingArgs};
 

crates/shared/cli-utils/src/metrics.rs

@@ -0,0 +1,101 @@
+//! Utility module to house implementation and declaration of MetricsArgs since it's being used in
+//! multiple places, it's just being referenced from this module.
+
+use std::net::IpAddr;
+
+use clap::Parser;
+
+use crate::{CliResult, PrometheusServer};
+
+/// Configuration for Prometheus metrics.
+#[derive(Debug, Clone, Parser)]
+#[command(next_help_heading = "Metrics")]
+pub struct MetricsArgs {
+    /// Controls whether Prometheus metrics are enabled. Disabled by default.
+    #[arg(
+        long = "metrics.enabled",
+        global = true,
+        default_value_t = false,
+        env = "BASE_METRICS_ENABLED"
+    )]
+    pub enabled: bool,
+
+    /// The port to serve Prometheus metrics on.
+    #[arg(long = "metrics.port", global = true, default_value = "9090", env = "BASE_METRICS_PORT")]
+    pub port: u16,
+
+    /// The IP address to use for Prometheus metrics.
+    #[arg(
+        long = "metrics.addr",
+        global = true,
+        default_value = "0.0.0.0",
+        env = "BASE_METRICS_ADDR"
+    )]
+    pub addr: IpAddr,
+}
+
+impl Default for MetricsArgs {
+    fn default() -> Self {
+        Self::parse_from::<[_; 0], &str>([])
+    }
+}
+
+impl MetricsArgs {
+    /// Initialize the tracing stack and Prometheus metrics recorder.
+    ///
+    /// This function should be called at the beginning of the program.
+    pub fn init_metrics(&self) -> CliResult<()> {
+        if self.enabled {
+            PrometheusServer::init(self.addr, self.port)?;
+        }
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::net::{IpAddr, Ipv4Addr};
+
+    use clap::Parser;
+
+    use super::*;
+
+    /// Helper struct to parse MetricsArgs within a test CLI structure.
+    #[derive(Parser, Debug)]
+    struct TestCli {
+        #[command(flatten)]
+        metrics: MetricsArgs,
+    }
+
+    #[test]
+    fn test_default_metrics_args() {
+        let cli = TestCli::parse_from(["test_app"]);
+        assert!(!cli.metrics.enabled, "Default for metrics.enabled should be false.");
+        assert_eq!(cli.metrics.port, 9090, "Default for metrics.port should be 9090.");
+        assert_eq!(
+            cli.metrics.addr,
+            IpAddr::V4(Ipv4Addr::new(0, 0, 0, 0)),
+            "Default for metrics.addr should be 0.0.0.0."
+        );
+    }
+
+    #[test]
+    fn test_metrics_args_from_cli() {
+        let cli = TestCli::parse_from([
+            "test_app",
+            "--metrics.enabled",
+            "--metrics.port",
+            "9999",
+            "--metrics.addr",
+            "127.0.0.1",
+        ]);
+        assert!(cli.metrics.enabled, "metrics.enabled should be true.");
+        assert_eq!(cli.metrics.port, 9999, "metrics.port should be parsed from CLI.");
+        assert_eq!(
+            cli.metrics.addr,
+            IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)),
+            "metrics.addr should be parsed from CLI."
+        );
+    }
+}