refactor: telemetry module

src/lib.rs

@@ -1,3 +1,4 @@
 pub mod configurations;
 pub mod routes;
 pub mod startup;
+pub mod telemetry;

src/main.rs

@@ -1,23 +1,17 @@
 use sqlx::PgPool;
 use std::net::TcpListener;
 use tracing::subscriber::set_global_default;
-use tracing_bunyan_formatter::{BunyanFormattingLayer, JsonStorageLayer};
 use tracing_log::LogTracer;
-use tracing_subscriber::{layer::SubscriberExt, EnvFilter, Registry};
-use zero2prod::{configurations::get_configuration, startup::run};
+use zero2prod::{configurations::get_configuration, startup::run, telemetry::get_subscriber};
 
 #[tokio::main]
 async fn main() -> Result<(), std::io::Error> {
     // Logger setup
     LogTracer::init().expect("Failed to set logger");
     // Info or above will be logged if the RUST_LOG environment variable is not set
-    let env_filter = EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new("info"));
-    let foirmatting_layer = BunyanFormattingLayer::new("zero2prod".into(), std::io::stdout);
-    let subscriber = Registry::default()
-        .with(env_filter)
-        .with(JsonStorageLayer)
-        .with(foirmatting_layer);
+    let subscriber = get_subscriber("zero2prod".into(), "info".into());
     set_global_default(subscriber).expect("Failed to set subscriber");
+
     // We want to panic if we cannot read the configuration
     let configuration = get_configuration().expect("Failed to read configurations");
     let connection = PgPool::connect(&configuration.database.get_connnection_string())

src/telemetry.rs

@@ -0,0 +1,34 @@
+use tracing::{subscriber::set_global_default, Subscriber};
+use tracing_bunyan_formatter::{BunyanFormattingLayer, JsonStorageLayer};
+use tracing_log::LogTracer;
+use tracing_subscriber::{layer::SubscriberExt, EnvFilter, Registry};
+
+/// Compose multiple layers into a `tracing`'s subscriber.
+///
+/// # Implementation Notes
+///
+/// We are using `impl Subscriber` as return type to avoid having to
+/// spell out the actual type of the returned subscriber, which is
+/// indeed quite complex.
+/// We need to explicitly call out that the returned subscriber is
+/// `Send` and `Sync` to make it possible to pass it to `init_subscriber`
+/// later on.
+pub fn get_subscriber(name: String, env_filter: String) -> impl Subscriber + Send + Sync {
+    let env_filter =
+        EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new(env_filter));
+    let formatting_layer = BunyanFormattingLayer::new(name.into(), std::io::stdout);
+    Registry::default()
+        .with(env_filter)
+        .with(JsonStorageLayer)
+        .with(formatting_layer)
+}
+
+/// Register a subscriber as global default to process span data.\
+///
+/// # Implementation Notes
+///
+/// It is important to call this function only once.
+pub fn inti_subscriber(subscriber: impl Subscriber + Send + Sync) {
+    LogTracer::init().expect("Failed to set logger");
+    set_global_default(subscriber).expect("Failed to set subscriber");
+}