feat: add optional JSON log format (#46)

* feat: add optional JSON log format via LOG_FORMAT env var

Set LOG_FORMAT=json to enable structured JSON logging output,
useful for log aggregation services like Datadog.

* style: cargo fmt

Author: Evrard-Nil

Cargo.lock

@@ -44,7 +44,7 @@ bytes = "1"
 thiserror = "2"
 anyhow = "1"
 tracing = "0.1"
-tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+tracing-subscriber = { version = "0.3", features = ["env-filter", "json"] }
 metrics = "0.24"
 metrics-exporter-prometheus = "0.18"
 

Cargo.toml

@@ -12,11 +12,19 @@ use vllm_proxy_rs::{
 #[tokio::main]
 async fn main() -> anyhow::Result<()> {
     // Initialize tracing
-    tracing_subscriber::fmt()
-        .with_env_filter(
-            tracing_subscriber::EnvFilter::try_from_default_env().unwrap_or_else(|_| "info".into()),
-        )
-        .init();
+    let env_filter =
+        tracing_subscriber::EnvFilter::try_from_default_env().unwrap_or_else(|_| "info".into());
+    let json_logs = std::env::var("LOG_FORMAT")
+        .map(|v| v.eq_ignore_ascii_case("json"))
+        .unwrap_or(false);
+    if json_logs {
+        tracing_subscriber::fmt()
+            .json()
+            .with_env_filter(env_filter)
+            .init();
+    } else {
+        tracing_subscriber::fmt().with_env_filter(env_filter).init();
+    }
 
     // Load config
     let config = config::Config::from_env()?;