add envconfig to parse envvars (#36)

capture-server/Cargo.toml

@@ -10,3 +10,4 @@ tokio = { workspace = true }
 tracing-subscriber = { workspace = true }
 tracing = { workspace = true }
 time = { workspace = true }
+envconfig = "0.10.0"

capture-server/src/main.rs

@@ -1,11 +1,22 @@
-use std::env;
+use envconfig::Envconfig;
 use std::net::SocketAddr;
 use std::sync::Arc;
 
 use capture::{billing_limits::BillingLimiter, redis::RedisClient, router, sink};
 use time::Duration;
 use tokio::signal;
 
+#[derive(Envconfig)]
+struct Config {
+    #[envconfig(default = "false")]
+    print_sink: bool,
+    #[envconfig(default = "127.0.0.1:3000")]
+    address: SocketAddr,
+    redis_url: String,
+    kafka_hosts: String,
+    kafka_topic: String,
+}
+
 async fn shutdown() {
     let mut term = signal::unix::signal(signal::unix::SignalKind::terminate())
         .expect("failed to register SIGTERM handler");
@@ -23,18 +34,15 @@ async fn shutdown() {
 
 #[tokio::main]
 async fn main() {
-    let use_print_sink = env::var("PRINT_SINK").is_ok();
-    let address = env::var("ADDRESS").unwrap_or(String::from("127.0.0.1:3000"));
-    let redis_addr =
-        env::var("REDIS_URL").expect("redis required; please set the REDIS_URL env var");
+    let config = Config::init_from_env().expect("Invalid configuration:");
 
     let redis_client =
-        Arc::new(RedisClient::new(redis_addr).expect("failed to create redis client"));
+        Arc::new(RedisClient::new(config.redis_url).expect("failed to create redis client"));
 
     let billing = BillingLimiter::new(Duration::seconds(5), redis_client.clone())
         .expect("failed to create billing limiter");
 
-    let app = if use_print_sink {
+    let app = if config.print_sink {
         router::router(
             capture::time::SystemTime {},
             sink::PrintSink {},
@@ -43,10 +51,7 @@ async fn main() {
             true,
         )
     } else {
-        let brokers = env::var("KAFKA_HOSTS").expect("Expected KAFKA_HOSTS");
-        let topic = env::var("KAFKA_TOPIC").expect("Expected KAFKA_TOPIC");
-
-        let sink = sink::KafkaSink::new(topic, brokers).unwrap();
+        let sink = sink::KafkaSink::new(config.kafka_topic, config.kafka_hosts).unwrap();
 
         router::router(
             capture::time::SystemTime {},
@@ -58,14 +63,14 @@ async fn main() {
     };
 
     // initialize tracing
-
     tracing_subscriber::fmt::init();
+
     // run our app with hyper
     // `axum::Server` is a re-export of `hyper::Server`
 
-    tracing::info!("listening on {}", address);
+    tracing::info!("listening on {}", config.address);
 
-    axum::Server::bind(&address.parse().unwrap())
+    axum::Server::bind(&config.address)
         .serve(app.into_make_service_with_connect_info::<SocketAddr>())
         .with_graceful_shutdown(shutdown())
         .await