feat: Add JSON log format for proper Datadog parsing

Configure env_logger to output structured JSON logs with timestamp,
level, target, and message fields. This ensures Datadog correctly
parses and categorizes log levels instead of treating all logs as
a single severity level.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: mantono

Cargo.lock

@@ -14,6 +14,7 @@ tokio = { version = "1", features = ["full"] }
 axum = { version = "0.6.18", features = ["headers", "http1", "json", "tokio", "query"] }
 log = { version = "0.4", optional = true }
 env_logger = { version = "0.11.8", optional = true }
+chrono = { version = "0.4", optional = true }
 clap = { version = "4.5.53", features = ["color", "derive", "help", "usage", "std", "env"] }
 redis = { version = "0.25.4", features = [ "ahash", "aio", "tokio-comp" ] }
 sha2 = "0.10.9"
@@ -23,5 +24,5 @@ tower = "0.4"
 
 [features]
 default = ["logging"]
-logging = ["dep:log", "dep:env_logger"]
+logging = ["dep:log", "dep:env_logger", "dep:chrono"]
 redis = []

Cargo.toml

@@ -21,6 +21,17 @@ async fn main() {
     env_logger::Builder::new()
         .target(env_logger::Target::Stdout)
         .filter_level(cfg.log_level().to_level_filter())
+        .format(|buf, record| {
+            use std::io::Write;
+            writeln!(
+                buf,
+                "{{\"timestamp\":\"{}\",\"level\":\"{}\",\"target\":\"{}\",\"message\":\"{}\"}}",
+                chrono::Utc::now().to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
+                record.level(),
+                record.target(),
+                record.args()
+            )
+        })
         .init();
 
     if cfg.api_key().is_none() {