feat: more info

Author: prestwich

src/utils/calc.rs

@@ -1,6 +1,8 @@
 use crate::utils::from_env::{FromEnv, FromEnvErr, FromEnvVar};
 use core::num;
 
+use super::from_env::EnvItemInfo;
+
 // Env vars
 pub(crate) const START_TIMESTAMP: &str = "START_TIMESTAMP";
 pub(crate) const SLOT_OFFSET: &str = "SLOT_OFFSET";
@@ -125,8 +127,24 @@ impl SlotCalculator {
 impl FromEnv for SlotCalculator {
     type Error = SlotCalcEnvError;
 
-    fn inventory() -> Vec<&'static str> {
-        vec![START_TIMESTAMP, SLOT_OFFSET, SLOT_DURATION]
+    fn inventory() -> Vec<&'static EnvItemInfo> {
+        vec![
+            &EnvItemInfo {
+                var: START_TIMESTAMP,
+                description: "The start timestamp of the chain",
+                optional: false,
+            },
+            &EnvItemInfo {
+                var: SLOT_OFFSET,
+                description: "The slot offset of the chain",
+                optional: false,
+            },
+            &EnvItemInfo {
+                var: SLOT_DURATION,
+                description: "The slot duration of the chain",
+                optional: false,
+            },
+        ]
     }
 
     fn from_env() -> Result<Self, FromEnvErr<Self::Error>> {

src/utils/from_env.rs

@@ -1,5 +1,18 @@
 use std::{convert::Infallible, env::VarError, num::ParseIntError, str::FromStr};
 
+/// Details about an environment variable. This is used to generate
+/// documentation for the environment variables and by the [`FromEnv`] trait to
+/// check if necessary environment variables are present.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct EnvItemInfo {
+    /// The environment variable name.
+    pub var: &'static str,
+    /// A description of the environment variable function in the CFG.
+    pub description: &'static str,
+    /// Whether the environment variable is optional or not.
+    pub optional: bool,
+}
+
 /// Error type for loading from the environment. See the [`FromEnv`] trait for
 /// more information.
 #[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]
@@ -93,8 +106,28 @@ pub trait FromEnv: core::fmt::Debug + Sized + 'static {
     /// Error type produced when loading from the environment.
     type Error: core::error::Error;
 
-    /// Get the environment variable names for this type.
-    fn inventory() -> Vec<&'static str>;
+    /// Get the required environment variable names for this type.
+    ///
+    /// ## Note
+    ///
+    /// This MUST include the environment variable names for all fields in the
+    /// struct, including optional vars.
+    fn inventory() -> Vec<&'static EnvItemInfo>;
+
+    /// Get a list of missing environment variables.
+    fn check_inventory() -> Result<(), Vec<&'static EnvItemInfo>> {
+        let mut missing = Vec::new();
+        for var in Self::inventory() {
+            if std::env::var(var.var).is_err() && !var.optional {
+                missing.push(var);
+            }
+        }
+        if missing.is_empty() {
+            Ok(())
+        } else {
+            Err(missing)
+        }
+    }
 
     /// Load from the environment.
     fn from_env() -> Result<Self, FromEnvErr<Self::Error>>;

src/utils/metrics.rs

@@ -1,6 +1,8 @@
 use crate::utils::from_env::{FromEnv, FromEnvErr, FromEnvVar};
 use metrics_exporter_prometheus::PrometheusBuilder;
 
+use super::from_env::EnvItemInfo;
+
 /// Metrics port env var
 const METRICS_PORT: &str = "METRICS_PORT";
 
@@ -40,8 +42,12 @@ impl From<u16> for MetricsConfig {
 impl FromEnv for MetricsConfig {
     type Error = std::num::ParseIntError;
 
-    fn inventory() -> Vec<&'static str> {
-        vec![METRICS_PORT]
+    fn inventory() -> Vec<&'static EnvItemInfo> {
+        vec![&EnvItemInfo {
+            var: METRICS_PORT,
+            description: "Port on which to serve metrics",
+            optional: true,
+        }]
     }
 
     fn from_env() -> Result<Self, FromEnvErr<Self::Error>> {

src/utils/otlp.rs

@@ -1,4 +1,4 @@
-use crate::utils::from_env::{FromEnv, FromEnvErr, FromEnvVar};
+use crate::utils::from_env::{EnvItemInfo, FromEnv, FromEnvErr, FromEnvVar};
 use opentelemetry::{trace::TracerProvider, KeyValue};
 use opentelemetry_sdk::trace::SdkTracerProvider;
 use opentelemetry_sdk::Resource;
@@ -110,8 +110,29 @@ pub struct OtelConfig {
 impl FromEnv for OtelConfig {
     type Error = url::ParseError;
 
-    fn inventory() -> Vec<&'static str> {
-        vec![OTEL_ENDPOINT, OTEL_LEVEL, OTEL_TIMEOUT, OTEL_ENVIRONMENT]
+    fn inventory() -> Vec<&'static EnvItemInfo> {
+        vec![
+            &EnvItemInfo {
+                var: OTEL_ENDPOINT,
+                description: "OTLP endpoint to send traces to",
+                optional: true,
+            },
+            &EnvItemInfo {
+                var: OTEL_LEVEL,
+                description: "OTLP level to export",
+                optional: true,
+            },
+            &EnvItemInfo {
+                var: OTEL_TIMEOUT,
+                description: "OTLP timeout in milliseconds",
+                optional: true,
+            },
+            &EnvItemInfo {
+                var: OTEL_ENVIRONMENT,
+                description: "OTLP environment name",
+                optional: true,
+            },
+        ]
     }
 
     fn from_env() -> Result<Self, FromEnvErr<Self::Error>> {