[Misc] add structure logging, write to file and log tracing for SGL Router

sgl-router/src/logging.rs

@@ -0,0 +1,163 @@
+use std::path::PathBuf;
+use tracing::Level;
+use tracing_appender::non_blocking::WorkerGuard;
+use tracing_appender::rolling::{RollingFileAppender, Rotation};
+use tracing_log::LogTracer;
+use tracing_subscriber::fmt::time::ChronoUtc;
+use tracing_subscriber::layer::SubscriberExt;
+use tracing_subscriber::util::SubscriberInitExt;
+use tracing_subscriber::{EnvFilter, Layer};
+
+/// Configuration for the logging system
+#[derive(Debug, Clone)]
+pub struct LoggingConfig {
+    /// Log level for the application (default: INFO)
+    pub level: Level,
+    /// Whether to use json format for logs (default: false)
+    pub json_format: bool,
+    /// Path to store log files. If None, logs will only go to stdout/stderr
+    pub log_dir: Option<String>,
+    /// Whether to colorize logs when output is a terminal (default: true)
+    pub colorize: bool,
+    /// Log file name to use if log_dir is specified (default: "sgl-router")
+    pub log_file_name: String,
+    /// Custom log targets to filter (default: "sglang_router_rs")
+    pub log_targets: Option<Vec<String>>,
+}
+
+impl Default for LoggingConfig {
+    fn default() -> Self {
+        Self {
+            level: Level::INFO,
+            json_format: false,
+            log_dir: None,
+            colorize: true,
+            log_file_name: "sgl-router".to_string(),
+            log_targets: Some(vec!["sglang_router_rs".to_string()]),
+        }
+    }
+}
+
+/// Guard that keeps the file appender worker thread alive
+///
+/// This must be kept in scope for the duration of the program
+/// to ensure logs are properly written to files
+#[allow(dead_code)]
+pub struct LogGuard {
+    _file_guard: Option<WorkerGuard>,
+}
+
+/// Initialize the logging system with the given configuration
+///
+/// # Arguments
+/// * `config` - Configuration for the logging system
+///
+/// # Returns
+/// A LogGuard that must be kept alive for the duration of the program
+///
+/// # Panics
+/// Will not panic, as initialization errors are handled gracefully
+pub fn init_logging(config: LoggingConfig) -> LogGuard {
+    // Forward logs to tracing - ignore errors to allow for multiple initialization
+    let _ = LogTracer::init();
+
+    // Convert log level to filter string
+    let level_filter = match config.level {
+        Level::TRACE => "trace",
+        Level::DEBUG => "debug",
+        Level::INFO => "info",
+        Level::WARN => "warn",
+        Level::ERROR => "error",
+    };
+
+    // Create env filter
+    let env_filter = EnvFilter::try_from_default_env().unwrap_or_else(|_| {
+        // Format: <target>=<level>,<target2>=<level2>,...
+        let filter_string = if let Some(targets) = &config.log_targets {
+            targets
+                .iter()
+                .enumerate()
+                .map(|(i, target)| {
+                    if i > 0 {
+                        format!(",{}={}", target, level_filter)
+                    } else {
+                        format!("{}={}", target, level_filter)
+                    }
+                })
+                .collect::<String>()
+        } else {
+            format!("sglang_router_rs={}", level_filter)
+        };
+
+        EnvFilter::new(filter_string)
+    });
+
+    // Setup stdout/stderr layer
+    let mut layers = Vec::new();
+
+    // Standard timestamp format: YYYY-MM-DD HH:MM:SS
+    let time_format = "%Y-%m-%d %H:%M:%S".to_string();
+
+    // Configure the console stdout layer
+    let stdout_layer = tracing_subscriber::fmt::layer()
+        .with_ansi(config.colorize)
+        .with_file(true)
+        .with_line_number(true)
+        .with_timer(ChronoUtc::new(time_format.clone()));
+
+    let stdout_layer = if config.json_format {
+        stdout_layer.json().flatten_event(true).boxed()
+    } else {
+        stdout_layer.boxed()
+    };
+
+    layers.push(stdout_layer);
+
+    // Create a file appender if log_dir is specified
+    let mut file_guard = None;
+
+    if let Some(log_dir) = &config.log_dir {
+        let file_name = config.log_file_name.clone();
+        let log_dir = PathBuf::from(log_dir);
+
+        // Create log directory if it doesn't exist
+        if !log_dir.exists() {
+            if let Err(e) = std::fs::create_dir_all(&log_dir) {
+                eprintln!("Failed to create log directory: {}", e);
+                return LogGuard { _file_guard: None };
+            }
+        }
+
+        let file_appender = RollingFileAppender::new(Rotation::DAILY, log_dir, file_name);
+
+        let (non_blocking, guard) = tracing_appender::non_blocking(file_appender);
+        file_guard = Some(guard);
+
+        let file_layer = tracing_subscriber::fmt::layer()
+            .with_ansi(false) // Never use ANSI colors in log files
+            .with_file(true)
+            .with_line_number(true)
+            .with_timer(ChronoUtc::new(time_format))
+            .with_writer(non_blocking);
+
+        let file_layer = if config.json_format {
+            file_layer.json().flatten_event(true).boxed()
+        } else {
+            file_layer.boxed()
+        };
+
+        layers.push(file_layer);
+    }
+
+    // Initialize the subscriber with all layers
+    // Use try_init to handle errors gracefully in case another subscriber is already set
+    let _ = tracing_subscriber::registry()
+        .with(env_filter)
+        .with(layers)
+        .try_init();
+
+    // Return the guard to keep the file appender worker thread alive
+    LogGuard {
+        _file_guard: file_guard,
+    }
+}